## How do I take screenshots on a development board?
Applicable to: OpenHarmony SDK 3.2.2.5, stage model of API version 9
- Method 1: Click the screenshot button in the Control Panel from the development board UI. The screenshot is displayed in Gallery.
- Method 2: Run the screenshot script. Connect to the development board to a computer running Windows. Create a text file on the computer, copy the following script content to the file, change the file name extension to **.bat** (the HDC environment variables must be configured in advance), and click **Run**. The screenshot is saved to the same directory as the **.bat** script file.
Example:
```
set filepath=/data/%date:~0,4%%date:~5,2%%date:~8,2%%time:~1,1%%time:~3,2%%time:~6,2%.png
echo %filepath%
: pause
hdc_std shell snapshot_display -f %filepath%
: pause
hdc_std file recv %filepath% .
: pause
```
## How do I adjust Previewer in DevEco Studio so that the preview looks the same as what's displayed on a real RK3568 development board?
## What should I do if Device Manager incorrectly identifies a development board as FT232R USB UART even when the development board already has a driver installed?
Possible cause: The USB serial driver of the development version is not installed.
Solution: Search for **FT232R USB UART**, and download and install the driver.
## How do I complete authentication when logging in to the development board?
Applicable to: OpenHarmony SDK 3.2.2.5
When connecting to the network that requires authentication, open any web page in the browser to access the authentication page.
If there is no browser on the development board, you can install the [sample browser application](https://gitee.com/openharmony/app_samples/tree/master/device/Browser).
## 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 ${this.myName.toUpperCase()}') // ok.
ForEach(this.arr.reverse(), ..., ...) // invalid: Array.reverse modifies the @State array varible in place
}
buildSpecial() // invalid: no function calls
Text(this.calcTextValue()) // this function call is ok.
}
```
## How do I use router to implement page redirection in the stage model?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
To implement page redirection through **router**, add all redirected-to pages to the pages list in the **main_pages.json** file.
Page routing APIs in **router** can be invoked only after page rendering is complete. Do not call these APIs in **onInit** or **onReady** when the page is still in the rendering phase.
## Will a page pushed into the stack through router.push be reclaimed?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
After being pushed to the stack through **router.push**, a page can be reclaimed only when it is popped from the stack through **router.back**.
## How do I dynamically replace the %s placeholder in a resource file?
Applicable to: OpenHarmony SDK 3.2.5.3, stage model of API version 9
In an application, you can replace the %s placeholder by using the second parameter in `$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($r('app.string.entry_desc','aaa'))
.fontSize(100)
.fontColor(Color.Black)
//do something
}
```
## How do I read an XML file in Resource and convert data in it to the string type?
Applicable to: OpenHarmony SDK 3.2.2.5, stage model of API version 9
1. Obtain data in Uint8Array format by calling the **RawFile** API of **resourceManager**.
2. Convert data in Uint8Array format to the string type by calling the **String.fromCharCode** API.
## What should I do if the global static variables of a class do not work?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Objects imported to abilities and pages are packaged into two different closures, that is, two global objects. In this case, a static variable referenced by the abilities is not the same object as that referenced by the pages. Therefore, global variables cannot be defined by defining static variables in the class. You are advised to use AppStorage to manage global variables.
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
The stage model allows an application to obtain a **ResourceManager** object based on **context** and call its resource management APIs without first importing the required bundle. This method, however, is not applicable to the FA model.
Example:
```
const context = getContext(this) as any
context
.resourceManager
.getString($r('app.string.entry_desc').id)
.then(value => {
this.message = value.toString()
})
```
## How do I position a container component to the bottom of the screen?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Create a **<Stack\>** component, and set the target container at the bottom of the **<Stack\>** component.
Example:
```
build() {
Stack({alignContent : Alignment.Bottom}) {
// The container is at the bottom.
Stack() {
Column()
.width('100%')
.height('100%')
.backgroundColor(Color.Yellow)
}
.width('100%')
.height('10%')
}
.width('100%')
.height('100%')
.backgroundColor('rgba(255,255,255, 0)')
}
```
## Can CustomDialog be used in TypeScript files?
Applicable to: OpenHarmony SDK 3.2.2.5, stage model of API version 9
No. Currently, **CustomDialog** can be used only on eTS pages.
## 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.
Example:
```
// CustomDialog component
@CustomDialog
struct MyDialog {
controller: CustomDialogController
title: string
data: string
cancel: () => void
confirm: (data: string) => void
Button('confirm')
.onClick(() => {
this.controller.close()
this.data = 'test'
this.confirm(this.data)
}).backgroundColor(0xffffff).fontColor(Color.Red)
// Page
@Entry
@Component
struct DialogTest {
dialogController: CustomDialogController = new CustomDialogController({
confirm: this.onAccept.bind(this)}), // Bind the custom callback to the button.
cancel: this.existApp,
autoCancel: true
})
onAccept(data:string) {
console.info('Callback when the second button is clicked ' + data)
}
}
```
## 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 taks 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](https://gitee.com/openharmony/docs/blob/master/zh-cn/application-dev/ui/ui-ts-layout-grid-container.md).
## How do I execute JavaScript functions in the \<Web> component in eTS code?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
Call the **runJavaScript** API in the **WebController** to asynchronously execute JavaScript scripts. This API uses a callback to return the execution result. Note: **runJavaScript** can only be called after **loadUrl** has been completed. For example, it can be called in **onPageEnd**.
## What are the differences between JavaScript, TypeScript, and eTS?
Applicable to: OpenHarmony SDK 3.2.3.5, stage model of API version 9
- JavaScript: a lightweight, weakly-typed programming language, most commonly known as the scripting language for web pages.
- TypeScript: a superset of JavaScript, with additions of static typing and more object-oriented APIs, enums, etc.
- eTS: a superset of TypeScript and the programming language for OpenHarmony ArkUI development, which powers UI development through a declarative development paradigm.
## How do I convert the time to the HHMMSS format?
