## Is a guide similar to the Data ability development in the FA model available for the stage model?
## How do I obtain a notification when the device orientation changes?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
A guide is available for the **DataShareExtensionAbility** class, which provides APIs for sharing data with other applications and managing the data, in the stage model.
Use the **UIAbility.onConfigurationUpdate\(\)** callback to subscribe to system environment variable changes (including the language, color mode, and screen orientation).
## What should I do if the UI does not respond when an ability is started?
**Reference**
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
[Subscribing to System Environment Variable Changes](../application-models/subscribe-system-environment-variable-changes.md#using-uiability-for-subscription)
1. If the ability is started using **startAbility**, check whether the **abilityName** field in **want** uses the bundle name as the prefix. If yes, delete the bundle name.
## How do I redirect a user to a specified page after they touch a service widget?
2. Make sure the ability's home page file configured by **onWindowStageCreate** in the **MainAbility.ts** file is defined in the **main_pages.json** file.
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
3. You are advised to use the SDK and OpenHarmony SDK versions released on the same day.
Configure a widget event with the redirected-to UIAbility specified, and call **loadContent** in the **onWindowStageCreate\(\)** callback of the target UIAbility to redirect to the specified page.
## How do I set the UI of an ability to transparent?
**Reference**
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
## Can I create a UIAbility and specify the process to run the UIAbility in the FA and Stage models?
.height('100%')
.backgroundColor('rgba(255,255,255, 0)')
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
}
```
**Solution**
Yes.
- FA model
The FA model supports multiple processes. By default, all components of an application run in the same process. This default scenario is suitable for most applications. To run a specific component in an independent process, configure the **process** tag under **ability** in the configuration file. Note that this tag is available only for system applications.
- Stage model
The stage model supports multiple processes. The process model is defined by the system, and third-party applications cannot be configured with multiple processes. To customize an independent process, you must request special permissions, and then specify the **process** tag under **module** in the configuration file. This tag specifies the process in which all the abilities in an HAP run. If this tag is not set, the bundle name is used as the process name by default.
## What are the differences between the stage model and the FA model in intra-process object sharing?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
- In the stage model, multiple application components share the same ArkTS engine instance. Therefore, they can easily share objects and state with each other. This also reduces the memory usage of complex applications.
- In the FA model, each application component exclusively uses an ArkTS engine instance. Therefore, you are advised to use the stage model when developing complex applications in distributed scenarios.
**Reference**
[Data Synchronization Between UIAbility and UI](../application-models/uiability-data-sync-with-ui.md)
## How do I use the lifecycle functions of AbilityStage?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
Add the field **"srcEntry": "./ets/myabilitystage/MyAbilityStage.ts"** under **module** in the **module.json5** file.
## How do I delete the mission snapshot in Recents after terminateself is called in the multiton scenario?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
You can set **removeMissionAfterTerminate** to **true** in the **module.json5** file.
## Why can't I start a UIAbility instance by using startAbility\(\)?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
- If the UIAbility is started using **startAbility**, check whether the **abilityName** field in **want** uses the bundle name as the prefix. If yes, delete the bundle name.
- Make sure the UIAbility's home page file configured by **onWindowStageCreate** in the **MainAbility.ts** file is defined in the **main\_pages.json** file. You are advised to use the SDK and OpenHarmony SDK versions released on the same day.
## How do I prevent "this" in a method from changing to "undefined" when the method is called?
## How do I prevent "this" in a method from changing to "undefined" when the method is called?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
Method 1: Add **.bind(this)** when calling the method.
Method 1: Add **.bind\(this\)** when calling the method.
Method 2: Use the arrow function.
Method 2: Use the arrow function.
## What should I do when the message "must have required property 'startWindowIcon'" is displayed?
## What should I do when the error message "must have required property 'startWindowIcon'" is displayed during the UIAbility startup?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
Configure the **startWindowIcon** attribute under **abilities** in the **module.json5** file.
Configure the **startWindowIcon** attribute under **abilities** in the **module.json5** file.
Example:
**Example**
```
```
{
{
...
@@ -77,138 +133,226 @@ Example:
...
@@ -77,138 +133,226 @@ Example:
}
}
```
```
## How do I obtain a notification when the device orientation changes?
**Reference**
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Implement the **onConfigurationUpdated** callback in the **Ability** class. The callback is triggered when the system language, color mode, or display parameters (such as the orientation and density) change.
## Can I obtain the context through globalThis in the stage model?
## Can I obtain the context through globalThis in the stage model?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
Do not use **globalThis** to obtain the context in the stage model.
This is because all the processes of an application share a JS VM instance in the stage model. Multiple abilities can run on these processes and share the same global object. If **globalThis** is used, the context of different abilities of the same JS VM instance may be returned.
**Reference**
[Data Synchronization Between UIAbility and UI](../application-models/uiability-data-sync-with-ui.md)
Do not use **globalThis** to obtain the context in the stage model. This is because all the processes of an application share a JS VM instance in the stage model. Multiple abilities can run on these processes and share the same global object. If **globalThis** is used, the context of different abilities of the same JS VM instance may be returned.
## What should I do when an error indicating too large size is reported during HAP deployment?
Reference of the recommended operation: [Context (Stage Model)](../application-models/application-context-stage.md)
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
## How do I obtain the HAP installation path of application B from application A?
**Symptom**
Applicable to: OpenHarmony SDK 3.0 or later, stage model of API version 9
During HAP deployment, the following error message is displayed:
First, request the system permission. For details, see [Having Your App Automatically Signed](https://developer.harmonyos.com/en/docs/documentation/doc-guides/ohos-auto-configuring-signature-information-0000001271659465). Then, import the **bundle** module, and call **bundle.getApplicationInfo()** to obtain application information based on the bundle name. Finally, use **application.moduleSourceDirs** to obtain the application storage path.
Failure\[INSTALL\_FAILED\_SIZE\_TOO\_LARGE\] error while deploying hap?
**Solution**
You can split the HAP into multiple HAPs.
## How is data returned when startAbilityForResult is called?
## How is data returned when startAbilityForResult is called?
Applicable to: OpenHarmony SDK3.0, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
The callee uses **AbilityContext.terminateSelfWithResult** to destroy its ability and pass parameters to **startAbilityForResult**. For details, see [AbilityContext](../reference/apis/js-apis-ability-context.md#abilitycontextterminateselfwithresult).
**Solution**
## Can the lifecycle callback of a released FA widget be triggered when the widget is displayed in the service center so that the user login information can be obtained without opening the FA application?
The target UIAbilities uses **AbilityContext.terminateSelfWithResult** to terminate itselef and pass the result to **startAbilityForResult**.
Applicable to: OpenHarmony SDK 3.2.5.5, FA model of API version 8
**Reference**
After a widget is added, the **oncreate()** lifecycle is triggered so that related user information (silent login) can be displayed even when the application is not started. However, users must manually add the widget after the application is installed.
[Starting UIAbility in the Same Application and Obtaining the Return Result](../application-models/uiability-intra-device-interaction.md)
## How do I obtain the context?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
## How do I obtain the system timestamp?
You can use **this.context** to obtain the context in the **MainAbility.ts** file or call **getContext(this)** to obtain the context on the component page.
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
## What should I do when undefined is displayed for the calling of **abilityAccessCtrl.grantUserGrantedPermission** during API version 8 syntax verification?
**Solution**
Applicable to: OpenHarmony SDK 3.0, FA model of API version 8
Use **getCurrentTime** of **@ohos.systemDateTime** to obtain the system time and time zone.
**abilityAccessCtrl.grantUserGrantedPermission** is a system API. It is not available in the public SDK, which is provided as default on DevEco Studio. To use system APIs, switch to the full SDK. For details, see [Guide to Switching to Full SDK](../quick-start/full-sdk-switch-guide.md).
**Example**
## Which of the following Extension abilities are available in the public SDK: ServiceExtensionAbility, FormExtensionAbility, and DataShareExtensionAbility?
Use the **@ohos.systemDateTime** API as follows:
Applicable to: OpenHarmony SDK 3.2.5.6, stage model of API version 9
console.info(`Failed to get currentTime. message: ${error.message}, code: ${error.code}`);
return;
}
console.info(`Succeeded in getting currentTime : ${time}`);
});
} catch(e) {
console.info(`Failed to get currentTime. message: ${e.message}, code: ${e.code}`);
}
```
Among the aforementioned Extension abilities, only **FormExtensionAbility** is available in the public SDK. **ServiceExtensionAbility** and **DataShareExtensionAbility** are system APIs and available only in the full SDK.
Public SDK: intended for application developers and does not contain system APIs that require system permissions.
**Reference**
Full SDK: intended for original equipment manufacturers (OEMs) and contains system APIs that require system permissions.
[System time and time zone] (../reference/apis/js-apis-system-date-time.md#systemdatetimegetcurrenttime)
## Why can't I play GIF images cyclically on the widget?
## How do I obtain the cache directory of the current application?
Applicable to: OpenHarmony SDK 3.2.5.6, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
The system does not support the display of GIF images on the widget.
**Solution**
## How do I implement service login by touching a widget?
Use **Context.cacheDir** to obtain the cache directory of the application.
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
**Reference**
You can start an ability upon the touch and implement service login in the ability.
[Obtaining the Application Development Path](../application-models/application-context-stage.md#obtaining-the-application-development-path)
## How do I redirect to the application details page in Settings?
## In which JS file is the service widget lifecycle callback invoked?
Applicable to: OpenHarmony SDK 3.2.6.5
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
Refer to the following code:
**Solution**
```
When a widget is created, a **FormAblity.ts** file is generated, which contains the widget lifecycle.
## What should I do when the compilation on DevEco Studio fails while ServiceExtensionAbility and DataShareExtensionAbility APIs are used?
```
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
let listener = mediaquery.matchMediaSync('(orientation: landscape)')
onPortrait(mediaQueryResult) {
**Symptom**
if (mediaQueryResult.matches) {
// Do something here.
After the **ServiceExtensionAbility** and **DataShareExtensionAbility** APIs are used, DevEco Studio reports an error indicating that the compilation fails.
} else {
// Do something here.
**Cause**
}
}
The following types of SDKs are provided:
listener.on('change', onPortrait)
```
- Public SDK: intended for application developers and does not contain system APIs that require system permissions.
- Full SDK: intended for original equipment manufacturers (OEMs) and contains system APIs that require system permissions.
The SDK downloaded using DevEco Studio is the public SDK.
**Solution**
Third-party application cannot use **ServiceExtensionAbility** and **DataShareExtensionAbility**. To develop a system application, first [download the full SDK](../quick-start/full-sdk-switch-guide.md).
## How do I obtain the temp and files paths at the application level?
Applicable to: OpenHarmony 3.2 Beta5
**Solution**
Obtain them from the application context. Specifically, use **this.context.getApplicationContext.tempDir** i to obtain the **temp** path, and use **this.context.getApplicationContext.filesDir** to obtain the **files** path.
**Reference**
[Obtaining the Application Development Path](../application-models/application-context-stage.md#obtaining-the-application-development-path)
## Can the lifecycle callback of a released FA widget be triggered when the widget is displayed in the service center so that the user login information can be obtained without opening the FA application?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
## How do I control the shadow background size during checkbox selection?
**Solution**
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
After a widget is added, the **onCreate()** lifecycle is triggered so that related user information (silent login) can be displayed even when the application is not started. However, users must manually add the widget after the application is installed.
Set the **padding** attribute of the **\<checkbox>** component to control the shadow size.
## How do I implement service login by touching a widget?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
To create a service widget in the FA model, perform the following steps:
1. Implement lifecycle callbacks for the widget.
2. Configure the widget configuration file.
3. Persistently store widget data.
## How do I set the widget background to transparent?
4. Update widget data.
Applicable to: OpenHarmony SDK 3.2.5.5
5. Develop the widget UI page.
1. Create the **widget/resources/styles/default.json** file in the root directory of the widget.
6. Develop a widget event. You can start a UIAbility upon the touch and implement service login in the UIAbility.
2. Add the following code to the **default.json** file:
**Reference**
[Widget Development in the FA Model](../application-models/widget-development-fa.md)
## How do I redirect to the application details page in Settings?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
## How do I get UIAbilityContext within the @Component component in the stage model?
Applicable to: OpenHarmony SDK 3.2.5.5
Use **featureAbility.getWant()** and **featureAbility.getContext()** to send data through **router** in the JSON file and use **featureAbility** to receive data in the JS file.
Applicable to: OpenHarmony 3.2 Beta5 (API version 9)
## How do I trigger router.disableAlertBeforeBackPage and router.enableAlertBeforeBackPage?
**Solution**
Applicable to: OpenHarmony SDK 3.2.5.5
You can use **UIAbility.Context** to obtain the context.
The following conditions must be met:
**Example**
1. Before the redirection to the previous page, a confirm dialog box will be displayed. Note that **router.disableAlertBeforeBackPage** is used to disable the display of a confirm dialog box before returning to the previous page (default), and **router.enableAlertBeforeBackPage** is used to enable the display.
```
import UIAbility from '@ohos.app.ability.UIAbility';
let UIAbilityContext = UIAbility.context;
let ApplicationContext = UIAbility.context.getApplicationContext();
## How do I determine whether an application is a system application?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
Use **bundleManager.getApplicationInfo** (available only for system applications) to obtain application information, and check the value of **systemApp** in the information. The application is a system application if the value is **true**.
## How do I obtain the version code and version name of an application?
Applicable to: OpenHarmony 3.2 Beta 5 (API version 9)
**Solution**
Use **bundleManager.getBundleInfoForSelf\(\)** to obtain the bundle information, which contains the version code (specified by **BundleInfo.versionCode**) and version name (specified by **BundleInfo.versionName**) .
**Example**
```
import bundleManager from '@ohos.bundle.bundleManager';
import hilog from '@ohos.hilog';
let bundleFlags = bundleManager.BundleFlag.GET_BUNDLE_INFO_DEFAULT;
[UIAbilityContext](../reference/apis/js-apis-inner-application-uiAbilityContext.md#uiabilitycontext) and [AbilityInfo](../reference/apis/js-apis-bundleManager-abilityInfo.md#abilityinfo)
## How do I obtain the application version number, version name, and screen resolution?
Applicable to: OpenHarmony 3.2 Beta5
**Solution**
1. Obtain the bundle information from the **@ohos.bundle.bundleManager** module.
The bundle information contains the application version number and version name.
```
import bundleManager from '@ohos.bundle.bundleManager';
## Can I obtain the HAP information of other applications from the current application?
Applicable to: OpenHarmony 3.2 Beta (API version 9)
According to the OpenHarmony security design specifications, the SDK does not provide APIs for third-party applications to obtain bundle information (including but not limited to the application name and version number) of other applications.
## How do I determine whether an application is a system application?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Use **bundle.getApplicationInfo** to obtain the application information, and then check the value of **systemApp** in the information. The application is a system application if the value is **true**.
## Why do the isStatusBarLightIcon and isNavigationBarLightIcon attributes not take effect when window.setSystemBarProperties() is called?
## How do I obtain the DPI of a device?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
Applicable to: OpenHarmony 3.2 Beta5 (API version 9, stage model)
In effect, the **isStatusBarLightIcon** and **isNavigationBarLightIcon** attributes turn the font white when set to **true**. If **statusBarContentColor** is also set in **window.setSystemBarProperties()**, the **isStatusBarLightIcon** attribute does not take effect. Similarly, if **navigationBarContentColor** is set, the **isNavigationBarLightIcon** attribute does not take effect.
**Solution**
## How do I set the style of the system bar?
Import the **@ohos.display** module and call the **getDefaultDisplaySync\(\)** API.
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
**Example**
Import the **\@ohos.window** module, and call **window.setSystemBarProperties()**.
console.error('Failed to enable the full-screen mode. Cause:' + JSON.stringify(err));
console.info('Succeeded in enabling the full-screen mode. Data: '+JSON.stringify(data));
return;
});
}
```
console.info('Succeeded in enabling the full-screen mode. Data: ' + JSON.stringify(data));
});
```
## How do I obtain the window width and height?
## How do I obtain the window width and height?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Applicable to: OpenHarmony SDK 3.2 Beta5 (API version 9, stage model)
Use **window.getProperties()** to obtain the window properties. The **windowRect** field in the properties specifies the window width and height.
**Solution**
Example:
Import the **@ohos.window** module, obtain a **Window** object, and use **getWindowProperties\(\)** of the object to obtain the window properties. The **windowRect** field in the properties specifies the window width and height.
**Example**
```ts
letpromise=windowClass.getProperties();
promise.then((data)=>{
console.info('Succeeded in obtaining the window properties. Data: '+JSON.stringify(data.windowRect));
}).catch((err)=>{
console.error('Failed to obtain the window properties. Cause: '+JSON.stringify(err));
});
```
```
import window from '@ohos.window';
## How do I set the color of the system bar?
let windowClass = null;
try {
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
## What should I do if the error message "npm ERR! code SELF_SIGNED_CERT_IN_CHAIN" is displayed?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
1. Run **npm config set strict-ssl=false** on the DevEco Studio terminal.
2. Run **npm install** on the DevEco Studio terminal.
## After manual updating of a DevEco Studio SDK, the error message "Cannot find module 'xxx\ets\x.x.x.x\build-tools\ArkTS-loader\node_modules\webpack\bin\webpack.js'" is displayed during HAP building. What should I do?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
1. Run **npm install** in the **ets\x.x.x.x\build-tools\ets-loader** directory of the SDK.
2. Run **npm install** in the **js\x.x.x.x\build-tools\ace-loader** directory of the SDK. Perform HAP building again.
## How do I pack a HAP file through the command line?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Method 1: Run **hvigor assembleHap**.
Method 2: In **scripts** of the project **package.json** file, define the build task script and run **npm buildOhosHaps**. The **buildOhosHaps** field can be customized.
```
"scripts": {
"buildOhosHaps": "hvigor assembleHap"
},
```
## How do I select API version 9 when creating a project in DevEco Studio?
Applicable to: DevEco Studio 3.0 Beta4 3.0.0.993(B06)
When creating a project in DevEco Studio, make sure you are on the **OpenHarmony** tab page.
## What should I do if no callback is received and no error code is returned for downloads?
Applicable to: all versions
1. Re-install hdc_std and set up the device connection again.
2. Run **hdc_std shell hilog -Q pidoff** to disable log log flow control.
## What should I do if the "error: unknow option. usage: aa start \<options>" message is displayed after I click Run in DevEco Studio?
Applicable to: OpenHarmony SDK 3.2.5.6, stage model of API version 9
This issue occurs when the parameter in the **aa** command is invalid and therefore the target application fails to be opened.
To fix this issue, use either of the following methods:
1. Make sure the SDK version and the OS version are the same.
2. Touch the application icon on the device to manually open the application.
## What should I do if "The hdc_std version of the SDK does not match the hdcd version of the device." message is displayed when I run an application in DevEco Studio?
Applicable to: OpenHarmony SDK 3.2.5.6, stage model of API version 9
This issue occurs when the hdc and hdcd versions do not match. Update Dev Eco Studio to 3.0.1.993 or later.
After the update, Dev Eco Studio will still indicate the version mismatch, but will not block the running.
## How do I add a custom .d.ts file to the OpenHarmony SDK?
Applicable to: OpenHarmony SDK 3.1.7.7, FA model of API version 8
Name the .d.ts file **@ohos.xxxx.d.ts**, save it to the SDK path, and restart Dev Eco Studio.
A code notification is displayed when the file is imported.
## How do I switch to the full SDK?
Applicable to: OpenHarmony SDK 3.2.7.5
Follow the instructions in [Guide to Switching to Full SDK](../quick-start/full-sdk-switch-guide.md).
## What are the restrictions on using generator functions in TypeScript?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
Below are the restrictions on using generator functions in TypeScript:
- Expressions can be used only in character strings (in the ${expression} format), **if** conditions, **ForEach** parameters, and component parameters.
- No expressions should cause any application state variables (including **@State**, **@Link**, and **@Prop**) to change. Otherwise, undefined and potentially unstable framework behavior may occur.
- The generator function cannot contain local variables.
None of the above restrictions apply to anonymous function implementations of event handlers (such as **onClick**).
Negative example:
```
build() {
let a: number = 1 // invalid: variable declaration not allowed
Column() {
Text('Hello ${this.myName.toUpperCase()}') // ok.
ForEach(this.arr.reverse(), ..., ...) // invalid: Array.reverse modifies the @State array variable in place
}
buildSpecial() // invalid: no function calls
Text(this.calcTextValue()) // this function call is ok.
}
```
## How do I dynamically replace the %s placeholder in a resource file?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
In an application, you can replace the %s placeholder by using the second parameter in **$r('app.string.xx')**, which is used to reference application resources.
Example:
```
build() {
//do something
// The second parameter indicates the referenced string resource, which can be used to replace the %s placeholder.
Text($r('app.string.entry_desc','aaa'))
.fontSize(100)
.fontColor(Color.Black)
//do something
}
```
## How do I read an XML file in Resource and convert data in it to the string type?
Applicable to: OpenHarmony SDK 3.2.2.5, stage model of API version 9
1. Obtain Uint8Array data by calling the **RawFile** API of **resourceManager**.
2. Convert the Uint8Array data to strings by calling the **String.fromCharCode** API.
## What should I do if the global static variables of a class do not work?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Objects imported to abilities and pages are packaged into two different closures, that is, two global objects. In this case, a static variable referenced by the abilities is not the same object as that referenced by the pages. Therefore, global variables cannot be defined by defining static variables in the class. You are advised to use AppStorage to manage global variables.
## How do I obtain resources in the stage model?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
The stage model allows an application to obtain a **ResourceManager** object based on **context** and call its resource management APIs without first importing the required bundle. This method, however, is not applicable to the FA model.
Example:
```
const context = getContext(this) as any
context
.resourceManager
.getString($r('app.string.entry_desc').id)
.then(value => {
this.message = value.toString()
})
```
## How do I obtain data through an API before page loading?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
In the **aboutToAppear** function, use an asynchronous API to obtain page data and **@State** to decorate related variables. After the data is obtained, the page is automatically refreshed based on the variables.
```
@Entry
@Component
struct Test6Page {
// After the data is obtained, the page is automatically refreshed.
@State message: string = 'loading.....'
aboutToAppear(){
// Simulate an asynchronous API to obtain data.
setTimeout(()=>{
this.message = 'new msg'
},3000)
}
build() {
Row() {
Column() {
Text(this.message)
.fontSize(50)
.fontWeight(FontWeight.Bold)
}
.width('100%')
}
.height('100%')
}
}
```
## Do the worker thread and the main thread run in the same global context?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
No. The worker thread and the main thread are not in the same global context. They interact with each other in data communication mode.
## Which API is used for URL encoding in OpenHarmony?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
The global function **encodeURI** is used for URI encoding, and **decodeURI** is used for URI decoding. For example, a space character is encoded as %20.
## Does OpenHarmony provide any API for parsing XML files?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Yes. The **convert** API of the **convertxml** module can be used to convert XML text into JavaScript objects.
## How do I configure application icons to be used across devices?
Applicable to: OpenHarmony SDK 3.0, stage model of API version 9
Use resource qualifiers to configure application icons to be used across devices.
## Can placeholders be configured in the string.json file of the stage model?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
The **string.json** file does not support placeholders. As an alternative, you can define variables on the target page and combine these variables and **Resource** objects.
## Is there any difference between the OpenHarmony API systemTime.getCurrentTime() and the JS API new Date().getTime() API?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
Similar to **new Date().getTime()**, **systemTime.getCurrentTime(false)** returns the number of milliseconds that have elapsed since the Unix epoch. **systemTime.getCurrentTime(true)** returns the number of nanoseconds that have elapsed since the Unix epoch. The system time is used in both APIs.
## How do I define @BuilderParam decorated attributes based on the value assigned to them?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
If no parameter is passed when assigning a value to the **@BuilderParam** decorated attribute (for example, **content: this.specificParam**), define the type of the attribute as a function without a return value (for example, **@BuilderParam content: () => voi**). If any parameter is passed when assigning a value to the **@BuilderParam** decorated attribute (for example, **callContent: this.specificParam1("111")**), define the type of the attribute as **any** (for example, **@BuilderParam callContent: any**).
## How does ArkTS convert a string into a byte array?
Applicable to: all versions
Refer to the following code:
```
function stringToByte(str) {
var bytes = new Array();
var len,c;
len = str.length;
for(var i = 0;i<len;i++) {
c = str.charCodeAt(i);
if( c >= 0x010000 && c<= 0x10FFFF) {
bytes.push(((c>>18) & 0x07) | 0xf0);
bytes.push(((c>>12) & 0x3F) | 0x80);
bytes.push(((c>>6) & 0x3f) | 0x80);
bytes.push((c & 0x3F) | 0x80);
} else if(c >= 0x000800 && c<= 0x00FFF){
bytes.push(((c>>12) & 0x07) | 0xf0);
bytes.push(((c>>6) & 0x3F) | 0x80);
bytes.push((c & 0x3F) | 0x80);
} else if(c >= 0x000800 && c<= 0x0007FF) {
bytes.push(((c>>6) & 0x3F) | 0x80);
bytes.push((c & 0x3F) | 0x80);
} else {
bytes.push(c & 0xFF)
}
}
return bytes;
}
```
## What do I do if the "Too many wokers, the number of worker exceeds the maximum" message is displayed during worker creation?
Applicable to: OpenHarmony SDK 3.2.6.5
An application allows for a maximum of seven workers. Therefore, use the **termiate** API to release workers when they are not needed.
## What is the difference between a @Builder decorated method and other methods?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
If the **@Builder** decorated method uses a custom component, this component is re-created each time the method is called.
## Why is the callback registered through @Watch not triggered when the object attributes of an array change?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
As with **@State**, the callback registered through **@Watch** can be used to listen for only one layer of data changes. If the object attributes of the array changes at the inner layer, the callback will not be triggered.
## How do I listen for in-depth changes of @State decorated variables?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
To listen for in-depth changes of **@State** decorated variables, you can use **@Observed** and **@ObjectLink** decorators.
## How do I implement character string encoding and decoding?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
You can use **TextEncoder** and **TextDecoder** provided by the **util** module.
Reference: [TextEncoder](../reference/apis/js-apis-util.md#textencoder) and [TextDecoder](../reference/apis/js-apis-util.md#textdecoder)
## How do i import and export namespaces?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
- Exporting namespaces
```
namespace Util{
export function getTime(){
return Date.now()
}
}
export default Util
```
- Importing namespaces
```
import Util from './util'
Util.getTime()
```
## Can relational database operations be performed in the worker thread?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
No. Relational database operations cannot be performed in the worker thread.
3. Process the obtained **PixelMap** object. For example, render and display the image.
## How do I apply for the media read/write permission on a device?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
1. Configure the permissions **ohos.permission.READ_MEDIA** and **ohos.permission.WRITE_MEDIA** in the **module.json5** file.
Example:
```
{
"module" : {
"requestPermissions":[
{
"name" : "ohos.permission.READ_MEDIA",
"reason": "$string:reason"
},
{
"name" : "ohos.permission.WRITE_MEDIA",
"reason": "$string:reason"
}
]
}
}
```
2. Call **requestPermissionsFromUser** to request the permissions from end users in the form of a dialog box. This operation is required because the grant mode of both permissions is **user_grant**.
```
import abilityAccessCtrl from '@ohos.abilityAccessCtrl.d.ts';
let permissions: Array<string> = ['ohos.permission.READ_MEDIA','ohos.permission.WRITE_MEDIA']
let atManager = abilityAccessCtrl.createAtManager();
// context is the ability-level context of the initiator UIAbility.
## How do I obtain the frame data of a camera when using the XComponent to display the preview output stream of the camera?
Applicable to: OpenHarmony 3.2 (API version 9, stage model)
**Symptom**
Currently, the API does not support real-time preview of the camera frame data. To obtain the frame data, you must bind an action, for example, photographing.
**Solution**
Create a dual-channel preview to obtain the frame data.
## How do I obtain the preview image of the front camera?
Applicable to: OpenHarmony 3.2 (API version 9, stage model)
**Solution**
1. Use the **@ohos.multimedia.camera** module to obtain the physical camera information.
```
let cameraManager = await camera.getCameraManager(context);
let camerasInfo = await cameraManager.getSupportedCameras();
let cameraDevice = this.camerasInfo[0];
```
2. Create and start the input stream channel of the physical camera.
```
let cameraInput = await cameraManager.createCameraInput(cameraDevice);
await this.cameraInput.open();
```
3. Obtain the output formats supported by the camera, and create a preview output channel based on the surface ID provided by the XComponent.
```
let outputCapability = await this.cameraManager.getSupportedOutputCapability(cameraDevice);
let previewProfile = this.outputCapability.previewProfiles[0];
let previewOutput = await cameraManager.createPreviewOutput(previewProfile, previewId);
```
4. Create a camera session, add the camera input stream and preview output stream to the session, and start the session. The preview image is displayed on the XComponent.
```
let captureSession = await cameraManager.createCaptureSession();
await captureSession.beginConfig();
await captureSession.addInput(cameraInput);
await captureSession.addOutput(previewOutput);
await this.captureSession.commitConfig()
await this.captureSession.start();
```
## How do I set the camera focal length?
Applicable to: OpenHarmony 3.2 (API version 9, stage model)
**Solution**
1. Check whether the camera is a front camera. A front camera does not support focal length setting.
2. Use **captureSession.getZoomRatioRange\(\)** to obtain the focal length range supported by the device.
3. Check whether the target focal length is within the range obtained. If yes, call **captureSession.setZoomRatio\(\)** to set the focal length.
## How do I play music in the background?
Applicable to: OpenHarmony 3.2 (API version 9, stage model)
**Symptom**
Music cannot be played in the background.
**Solution**
**AVSession** controls media playback. When a third-party application switches to the background or encounters a screen lock event, media playback is forcibly paused and the application is unaware of the pause. To enable the application to continue the playback in the background, request a continuous task and access the AVSession capability, which allows Control Panel to control the playback behavior of third-party applications.
## Is there a native API that provides functions similar to Canvas?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
Yes. The native API **Drawing** provides similar functions. It can be used for 2D drawing.
## When a native HAP is running, the error message "Obj is not a valid object" is displayed for the imported namespace. What should I do?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
Check the **abiFilters** parameter value in the **build-profile.json5** file in the root directory of the module (not the root directory of the project). If the device is 32-bit, the value must be **armeabi-v7a**. If the device is 64-bit, the value must be **arm64-v8a**.
## What should I do when the error message "install parse profile prop check error" is displayed during the running of a native HAP?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
Check the **abiFilters** parameter value in the **build-profile.json5** file in the root directory of the module (not the root directory of the project). If the device is 32-bit, the value must be **armeabi-v7a**. If the device is 64-bit, the value must be **arm64-v8a**.
## What should I do when the error message "undefined symbol: OH_LOG_Print" is displayed during log printing by **OH_LOG_Print**?
Applicable to: OpenHarmony SDK 3.2.6.3, stage model of API version 9
Modify the **CMakeLists.txt** file by adding **libhilog_ndk.z.so** to the end of **target_link_libraries**.
## How do I obtain the value of version in the package.json file of a module?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
1. In the script file **hvigorfile.js** of Hvigor, use **subModule.getPackageJsonPath** to obtain the location of the **package.json** file in the module.
2. Use Node.js to read the **version** field in the **package.json** file and write the value to the **buildOption.cppFlags** field in the **build-profile.json5** file.
const ohosPlugin = require('@ohos/hvigor-ohos-plugin').hapTasks(subModule) // The plug-in executes the C++ build task and reads the build-profile.json5 file.
## Are the APIs used for obtaining PPG and ECG sensor data open to individual developers?
Applicable to: OpenHarmony 3.1 Beta 5 (API version 9)
Data collected by the PPG and ECG sensors of wearable devices is personal privacy data. Therefore, relative APIs are not open to individual developers.
## How do I obtain available third-party libraries?
Applicable to: OpenHarmony 3.1 Beta 5 (API version 9)
The three-party and four-party libraries that can be obtained through ohpm are summarized in the [OpenHarmony-TPC/tpc_resource repository](https://gitee.com/openharmony-tpc/tpc_resource). You can access this repository, and find the desired component based on the directory index.
## Which third-party libraries are related to network requests?
Applicable to: OpenHarmony 3.1 Beta 5 (API version 9)
The following third-party libraries are related to network requests: [Axios](https://gitee.com/openharmony-sig/axios), httpclient, and okdownload. For details, see the [OpenHarmony-TPC/tpc_resource repository](https://gitee.com/openharmony-tpc/tpc_resource).
## How do I use ohpm to import third- and fourth-party libraries?
Applicable to: OpenHarmony 3.1 Beta 5 (API version 9)
**Solution**
- Method 1:
1. Open the **Terminal** window and run the following command to go to the **entry** directory:
```
cd entry
```
2. Run the following command to install a third-party library, for example, **dayjs**:
```
ohpm install dayjs
```
3. Add the following statement in the .js file to import the third-party library:
```
import dayjs from 'dayjs';
```
- Method 2:
1. Enter the **entry** directory of the project and open the **oh-package.json5** file.
2. Write the third-party library to be installed (for example, **dayjs**) in the **oh-package.json5** file.
```
{
"dependencies": {
"dayjs": "^1.10.4",
}
}
```
3. Open the **Terminal** window and run the following command to go to the **entry** directory:
```
cd entry
```
4. Run the following command to install the third-party library:
```
ohpm install
```
5. Add the following statement in the .js file to import the third-party library:
## What does the following error message mean: "Stage model module... does not support including OpenHarmony npm packages or modules in FA model. OpenHarmony build tasks will not be executed, and OpenHarmony resources will not be packed."
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
The third- and fourth-party libraries are not yet compatible with the stage model of API version 9 and cannot be used.
## Can I transfer project-level dependencies?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
For example, if project A depends on project B and project B depends on project C, can project A directly use the APIs provided by project C?
No. Project A cannot directly use the APIs provided by project C. The project packing tool NPM does not support dependency transfer. To use the APIs provided by project C, you can add the dependency of project C to project A.
## How do I obtain available third-party libraries?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
For details, see [Third-Party Components That Can Be Directly Used on OpenHarmony](https://gitee.com/openharmony-sig/third_party_app_libs).
## Which third-party libraries are related to network requests?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The [Axios](https://gitee.com/openharmony-sig/axios) library is related to network requests.
## How do I use NPM to import third- and fourth-party libraries?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
- Method 1:
1. Open the **Terminal** window and run the following command to go to the **entry** directory:
```
cd entry
```
2. Run the following command to install a third-party package, for example, **dayjs**:
```
npm install dayjs --save
```
3. Add the following statement in the .js file to import the package:
```
import dayjs from 'dayjs';
```
- Method 2:
1. Enter the **entry** directory of the project and open the **package.json** file.
2. Write the third-party NPM package to be installed (for example, **dayjs**) in the **package.json** file.
```
{
"dependencies": {
"dayjs": "^1.10.4",
}
}
```
3. Open the **Terminal** window and run the following command to go to the **entry** directory:
```
cd entry
```
4. Run the following command to install NPM:
```
npm install
```
5. Add the following statement in the .js file to import the package:
## How do I use router to implement page redirection in the stage model?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
1. To implement page redirection through **router**, add all redirected-to pages to the pages list in the **main_pages.json** file.
2. Page routing APIs in **router** can be invoked only after page rendering is complete. Do not call these APIs in **onInit** or **onReady** when the page is still in the rendering phase.
## How do I transfer variables in CustomDialog to variables on pages?
Applicable to: OpenHarmony SDK 3.2.2.5, stage model of API version 9
Use a custom callback so that when the confirm button in the custom dialog box is clicked, the value of **data** is transferred from the dialog box to the current page.
this.dialogData = data //Obtain the data in the text box.
})
}.width("100%")
}.height("100%")
}
}
```
## What should I do if the \<List> component cannot be dragged to the bottom after it has a \<Text> component added?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
The **\<List>** component is a scrollable container. By default, it takes up the entire screen height. When any component with a fixed height takes up part of the screen height, you need to explicitly specify **layoutWeight(1)** for the parent container of the **\<List>** component to take up the remaining height instead of the entire screen height.
## How do I center child components in a grid container?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
By default, child components in a **\<GridContainer>** are horizontally aligned to the left. To center them, perform the following steps:
Nest a **\<Row>** component and set it to **justifyContent(FlexAlign.Center)**. For details, see [Grid Layout](../reference/arkui-ts/ts-container-gridcontainer.md).
## How do I obtain the value of param for the target page of redirection implemented using router?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
```ts
// In versions earlier than 3.1.5.5, obtain the value through router.getParams().key.
privatevalue:string=router.getParams().value;
// In 3.1.6.5 and later versions, obtain the value through router.getParams()['key'].
privatevalue:string=router.getParams()['value'];
```
## Does the \<RichText> component support redirection to a local page?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
No. This feature is not supported.
## How do I disable the transition effect for pages switched using router or navigator?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
1. Define the **pageTransition** method for the current and target pages, by following instructions in [Example](../reference/arkui-ts/ts-page-transition-animation.md#example).
2. Set the **duration** parameter of both **PageTransitionEnter** and **PageTransitionExit** to **0**.
## How do I select the pixel unit during UI development?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
It depends.
The vp unit ensures consistency of visual effects across resolutions. For example, it ensures that an icon is displayed consistently under different resolutions.
The lpx unit produces a visual effect where items are zoomed in or out proportionally.
If you are concerned about visual effect consistency of items, for example, buttons, texts, and lists, use the vp unit. If your focus is on the layout, for example, 1/2 grid, the lpx is a better choice.
## What color formats are used in ArkTS?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
The color can be represented in two formats, for example, 0x7F000000 or '\#7F000000'. The first two digits indicate opacity, and the last six digits indicate RGB.
```ts
fontColor(0x7F000000)
fontColor('#7F000000')
```
## How do I listen for the return operation on a page?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
When a return operation is performed on a page, the system calls the **onBackPress()** callback of the **@Entry** decorated custom component. You can implement related service logic in the callback.
## Can I customize the eye icon for the \<TextInput> component in password mode?
Applicable to: OpenHarmony SDK 3.0, stage model of API version 9
No. The eye icon can be shown or hidden through **showPasswordIcon** when **type** of the **\<TextInput>** component is set to **InputType.Password**. It cannot be customized.
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
HTTP is insecure and HTTP sources will be filtered out by the trustlist. For security purposes, use HTTPS.
## What should I do if the spacing set for the TextView layout does not fit the UI?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
By default, the **align** attribute of **TextView** is set to **Center**. To display the text from left to right, set the **align** attribute to **Start**.
## Why do the constraintSize settings fail to take effect?
Applicable to: OpenHarmony SDK 3.0, stage model of API version 9
If **constraintSize** is set for a component and the width of its child component is set to a percentage, for example, **width('100%')**, **constraintSize** takes effect by multiplying the maximum width by the percentage. As a result, the child component may overflow, in which case it looks like the **constraintSize** settings fail to take effect.
## How do I set the background color to transparent?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Set **backgroundColor** to **'\#00000000'**.
## What should I do if the \<Scroll> component cannot scroll to the bottom?
Applicable to: OpenHarmony SDK 3.0, stage model of API version 9
Unless otherwise specified, the height of the **\<Scroll>** component is equal to the window height. In this case, the component's bottom area will be blocked by components (if any) outside of it. To fix this issue, set the height of the **\<Scroll>** component or use the flex layout to limit this height.
## How do I use the onSubmit event of the \<TextInput> component?
Applicable to: OpenHarmony SDK 3.0, stage model of API version 9
The **onSubmit** event is triggered when the Enter key is pressed and accepts the current Enter key type as its input parameter. You can set the Enter key type for the **\<TextInput>** component through the **enterKeyType** attribute. The Enter key style of the soft keyboard requires the support of the input method.
## What is the maximum number of pages allowed during page routing?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The maximum number of pages supported by the page stack is 32. When this limit is reached, the **router.push** API cannot be used for page redirection.
## Does ArkUI allow components to be dynamically created in code?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
Yes. You can dynamically creaete components using [conditional rendering](../quick-start/arkts-rendering-control.md#conditional-rendering) and [loop rendering](../quick-start/arkts-rendering-control.md#loop-rendering).
## What should I do if the PixelMap object carried in page routing cannot be obtained from the target page?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
Page routing supports only the common object type and common JSON data structure. To pass a **PixelMap** object to the target page, store it in the **localStorage**.
## How do I use .caretPosition(0) to move the caret to the start of the text area when onEditChange is triggered for the \<TextInput> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The **onEditChange** event is triggered when the input box gains focus. Under this scenario, the caret position is related to the position where the gesture is when the event is triggered, and **caretPosition** cannot be used to change the caret position. Call **setTimeout** for asynchronous processing first.
## Is there any method for selecting all items in the \<TextInput> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
No. This feature is not supported yet.
## Why can't I select a date when the type attribute of the input text box is set to date?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
Setting the **type** attribute of the input component to **date** means that the component accepts dates as input and the user will be notified of the valid input format. It does not display a date picker. To display a date picker, use the **\<DatePicker>** component.
## What should I do if the displayed input keyboard gets squeezed when using the **\<TextInput>** component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
This issue may occur when the flex layout is used. To fix it, switch to the column layout.
## How does the parent component pass values to a @Link decorated member variable in its child component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
To pass a value from the parent component to the **@Link** decorated member variable in a child component, add **"$"** in front of the value.
## How do I share variables between Page abilities?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
1. Use a lightweight database.
2. Use persistent data management.
3. Use the emitter event communication mechanism.
## How do I customize the control bar style of the \<Video> component?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
1. Set **controls** to **false** to disable the default control bar.
2. Set **controller** for the **\<Video>** component.
3. Implement a custom control bar in ArkTS and use **VideoController** to control video playback.
## How do I optimize the performance when an ArkTS component is to be updated for multiple times?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Extract the ArkTS component to be updated into a custom component and update the **@State** decorated variables in the custom component to implement partial refresh.
## How do I optimize the \<Tab> component performance?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
When the **\<Tab>** component is on a tab page, other tab pages are not unloaded by the system and still occupy some memory. To improve performance, you can use **if** to check whether the current tab page is being displayed and unload it if it is not. In this way, the tab pages not being displayed can be unloaded and the memory occupied by them can be released.
## How do I set state-specific styles for a component?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
You can use the polymorphic style attribute to set styles of the component for different states (being stateless, in pressed state, in disabled state, in focused state, or in clicked state).
## Why can't the onBlur or onFocus callback be triggered?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
Only the Tab button and arrow buttons on the connected keyboard can be used to trigger the focus event. In addition, to trigger a focus event by a touch, the **focusOnTouch** attribute must be added for the component.
## What should I do if the flex width and height in the \<Scroll> component conflicts with the scrolling?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The **\<Scroll>** component supports a single child component, whose height is subject to the content height. If the scrolling layout is abnormal due to asynchronous loading of an image within the content, you can set the minimum height for the child component through **constraintSize({ minHeight: '100%' })**.
## How do I block the page router from returning to the previous page?
Applicable to: OpenHarmony SDK 3.2.5.5, stage model of API version 9
Call **router.clear()** to remove all historical pages in the page stack and retain the current page at the top of the stack.
## Can tab switching be disabled for the \<Tabs> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
No. This feature is not supported.
## An error is reported when @state is used to decorate the id member variable: "TypeError: cannot read property 'get' of undefined." Why?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The ID has been added as a unique value and becomes a keyword.
## Can I use the fontFamily attribute to set different fonts for OpenHarmony applications?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
No. For applications developed based on OpenHarmony, the default font and also the only supported font is HarmonyOS Sans.
## What is the recommended data interaction mode between an ability and UI page?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
[LocalStorage](../quick-start/arkts-state-mgmt-application-level.md#localstorage) is recommended.
## How does a parent component synchronize status with its grandchild components?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
- Method 1 (recommended): Use the **@Provide** and **@Consume** decorators. Specifically, use **@Provide** in the parent component and **@Consume** in the grandchild component to implement two-way data binding between the components.
- Method 2: Use the **@State** and **@Link** decorators. Specifically, use **@State** in the parent component, and **@Link** in all involved child and grandchild components.
## How do I display an ellipsis in cases when the string is too long to display in full?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
Example:
```
beautySub(str,len) {
var reg = /[\u4e00-\u9fa5]/g;
// Reduce characters whenever possible.
var slice = str.substring(0,len)
var charNum = (~~(slice.match(reg) && slice.match(reg).length))
// The purpose of charNum-1 is to process the string that exceeds the maximum value. If the string exceeds the maximum value, the character that is not in current language is not displayed.
## How do I add a scrollbar to the \<richText> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The **\<RichText>** component is underpinned by web. To add a scrollbar, you can refer to the HTML syntax and add the **overflow: auto** style to **div**.
## How do I disable the scroll event of a grid in the \<Scroll> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
You can use the **onScrollBegin** event and the **scrollBy** method to implement nested scrolling of the containers.
## Can the white background of the custom dialog box be removed?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
No. This feature is not supported. The UI style is hardcoded in the framework and cannot be changed.
## Does the **backgroundImage** API support the SVG image format?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
No. This image format is not supported.
## How do I set the position for a custom dialog box?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
You can set the position for a custom dialog box through the **alignment** parameter. For example, to set the custom dialog box to show at the bottom, set **alignment** to **DialogAlignment.Bottom**.
## How does the scroller determine the end error of the rebound animation?
Applicable to: OpenHarmony SDK 3.2.5.3, FA model of API version 8
After the touch ends, a change in the same direction may be calculated. If the change is in the opposite direction, it indicates that a rebound occurs, and no processing is performed.
## How do I implement persistent storage of application data?
Use the **PersistentStorage** class to manage persistent application data. Persistent data with specific tags can be linked to the **AppStorage** and accessed through the **AppStorage** APIs.
## What is the domStorageAccess attribute of the \<Web> component used for?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The **domStorageAccess** attribute specifies whether to enable the DOM Storage API, which is disabled by default and provides **localStorage**, but not **sessionStorage**.
## How do I check the online status on the HTML page loaded by the \<Web> component?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
1. Configure the **ohos.permission.INTERNET** and **ohos.permission.GET_NETWORK_INFO** application permissions.
2. Obtain the online status through **window.navigator.onLine** on the HTML page.
## What should I do if the UserAgent string cannot be used in concatenation before the initial HTML5 page loading by the \<Web> component?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
By default, the **UserAgent** string is obtained through the **WebController**. A **WebController** object can control only one **\<Web>** component, and methods on the **WebController** can only be called by the **\<Web>** component bound to it. To concatenate the default **UserAgent** string and a custom string before the initial page loading, perform the following:
1. Use **@State** to define the initial **userAgent** and bind it to the **\<Web>** component.
2. In the **onUrlLoadIntercept** callback of the **\<Web>** component, use **WebController** to obtain the default **userAgent** string and modify the **userAgent** bound to the **\<Web>** component.
The code snippet is as follows:
```
@Entry
@Component
struct Index {
private controller: WebController = new WebController()
## Should the logic for loading the lottie animation be written in the onAppear or onReady function?
Applicable to: OpenHarmony SDK 3.2.6.5, stage model of API version 9
The logic for loading the lottie animation must be written in the **onReady** function. The **onReady** function is triggered when the canvas is ready, while the **onAppear** function is triggered when the canvas is displayed.
## Do I need to invoke the refresh API after invoking deleteJavaScriptRegister?
Applicable to: all versions
No. This operation is not needed.
## How do I pass data from a page to the \<Web> component?
Applicable to: OpenHarmony SDK 3.2.7.5, stage model of API version 9
1. Use **WebController** to create two message ports: message port 1 and message port 0.
2. Send message port 1 to the HTML side, which can then save and use the port.
3. Register a callback for message port 0 on the application side.
4. Use message port 0 on the application side to send messages to message port 1 on the HTML side.
letavoidAreaRect=data.regionTint[0].region;// data.regionTint is an array that contains the rectangle coordinates of the status bar and navigation bar.
