[Context](../reference/apis/js-apis-inner-application-context.md) is the context of an object in an application. It provides basic information about the application, for example, **resourceManager**, **applicationInfo**, **dir** (application development path), and **area** (encrypted level). It also provides basic methods such as **createBundleContext()** and **getApplicationContext()**. The UIAbility component and ExtensionAbility derived class components have their own **Context** classes, for example, the base class **Context**, **ApplicationContext**, **AbilityStageContext**, **UIAbilityContext**, **ExtensionContext**, and **ServiceExtensionContext**.
[Context](../reference/apis/js-apis-inner-application-context.md) is the context of an object in an application. It provides basic information about the application, for example, **resourceManager**, **applicationInfo**, **dir** (application file path), and **area** (encryption level). It also provides basic methods such as **createBundleContext()** and **getApplicationContext()**. The UIAbility component and ExtensionAbility derived class components have their own **Context** classes, for example, the base class **Context**, **ApplicationContext**, **AbilityStageContext**, **UIAbilityContext**, **ExtensionContext**, and **ServiceExtensionContext**.
- The figure below illustrates the inheritance relationship of contexts.
- The figure below illustrates the holding relationship of contexts.
The following describes the information provided by different contexts.
-The following describes the information provided by different contexts.
-[UIAbilityContext](../reference/apis/js-apis-inner-application-uiAbilityContext.md): Each UIAbility has the **Context** attribute, which provides APIs to operate an application component, obtain the application component configuration, and more.
```ts
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@@ -67,63 +70,68 @@ The following describes the information provided by different contexts.
This topic describes how to use the context in the following scenarios:
-[Obtaining the Application Development Path](#obtaining-the-application-development-path)
-[Obtaining and Modifying Encryption Levels](#obtaining-and-modifying-encryption-levels)
-[Creating Context of Another Application or Module](#creating-context-of-another-application-or-module)
-[Subscribing to UIAbility Lifecycle Changes in a Process](#subscribing-to-uiability-lifecycle-changes-in-a-process)
### Obtaining the Application Development Path
### Obtaining Application File Paths
The following table describes the application development paths obtained from context.
The base class [Context](../reference/apis/js-apis-inner-application-context.md) provides the capability of obtaining application file paths. **ApplicationContext**, **AbilityStageContext**, **UIAbilityContext**, and **ExtensionContext** inherit this capability. The application file paths are a type of application sandbox paths. For details, see [Application Sandbox Directory](../file-management/app-sandbox-directory.md).
**Table 1** Application development paths
The application file paths obtained by the preceding contexts are different.
| bundleCodeDir | string | Yes | No | Path for storing the application's installation package, that is, installation directory of the application on the internal storage. |
| cacheDir | string | Yes| No| Path for storing the cache files, that is, cache directory of the application on the internal storage.<br>It is the content of **Storage** of an application under **Settings > Apps & services > Apps**.|
| filesDir | string | Yes | No | Path for storing the common files, that is, file directory of the application on the internal storage.<br>Files in this directory may be synchronized to other directories during application migration or backup.|
| preferencesDir | string | Yes | Yes | Path for storing the preference files, that is, preferences directory of the application. |
| tempDir | string | Yes | No | Path for storing the temporary files.<br>Files in this directory are deleted after the application is uninstalled.|
| databaseDir | string | Yes | No | Path for storing the application's database, that is, storage directory of the local database. |
| distributedFilesDir | string | Yes| No| Path for storing the distributed files.|
- The application file path obtained through **ApplicationContext** is at the application level. This path is recommended for storing global application information, and the files in the path will be deleted when the application is uninstalled.
The capability of obtaining the application development path is provided by the base class **Context**. This capability is also provided by **ApplicationContext**, **AbilityStageContext**, **UIAbilityContext**, and **ExtensionContext**. However, the paths obtained from different contexts may differ, as shown below.
**Figure 1** Application development paths obtained from context
The sample code is as follows:
```ts
import UIAbility from '@ohos.app.ability.UIAbility';
export default class EntryAbility extends UIAbility {
onCreate(want, launchParam) {
let applicationContext = this.context.getApplicationContext();
let cacheDir = applicationContext.cacheDir;
let tempDir = applicationContext.tempDir;
let filesDir = applicationContext.filesDir;
let databaseDir = applicationContext.databaseDir;
let bundleCodeDir = applicationContext.bundleCodeDir;
let distributedFilesDir = applicationContext.distributedFilesDir;
let preferencesDir = applicationContext.preferencesDir;
...
}
}
```
- The application file path obtained through **AbilityStageContext**, **UIAbilityContext**, or **ExtensionContext** is at the HAP level. This path is recommended for storing HAP-related information, and the files in this path are deleted when the HAP is uninstalled. However, the deletion does not affect the files in the application-level path unless all HAPs of the application are uninstalled.
- Obtain the application-level path through **ApplicationContext**. It is recommended that global application information be stored in this path. Files stored in this path will be deleted only when the application is uninstalled.
- Obtain the HAP level path through **AbilityStageContext**, **UIAbilityContext**, and **ExtensionContext**. It is recommended that the HAP information be stored in this path. The file content stored in this path will be deleted when the HAP is uninstalled. The file content in the application-level path will be deleted only after all the HAPs of the application are uninstalled.
> The sample code obtains the sandbox path of the application development path. The absolute path can be obtained by running the **find / -name <fileName>** command in the hdc shell after file creation or modification.
### Obtaining and Modifying Encryption Levels
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@@ -153,22 +158,23 @@ In practice, you need to select a proper encryption level based on scenario-spec
>
> - AreaMode.EL2: user-level encryption. Directories with this encryption level are accessible only after the device is powered on and the password is entered (for the first time).
You can obtain and set the encryption level by reading and writing the [area attribute in Context](../reference/apis/js-apis-inner-application-context.md).
You can obtain and set the encryption level by reading and writing the **area** attribute in [Context](../reference/apis/js-apis-inner-application-context.md).
### Creating Context of Another Application or Module
The base class **Context** provides [createBundleContext(bundleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatebundlecontext), [createModuleContext(moduleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatemodulecontext), and [createModuleContext(bundleName:string, moduleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatemodulecontext-1) to create the context of other applications or modules, so as to obtain the resource information, for example, [obtaining the application development paths](#obtaining-the-application-development-path) of other modules.
The base class **Context** provides [createBundleContext(bundleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatebundlecontext), [createModuleContext(moduleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatemodulecontext), and [createModuleContext(bundleName:string, moduleName:string)](../reference/apis/js-apis-inner-application-context.md#contextcreatemodulecontext-1) to create the context of other applications or modules, so as to obtain the resource information, for example, [obtaining application file paths](#obtaining-application-development-paths) of other modules.
- Call **createBundleContext(bundleName:string)** to create the context of another application.
