# ApplicationContext The **ApplicationContext** module provides application-level context. You can use the APIs of this module to register and deregister the ability lifecycle listener in an application. > **NOTE** > > The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version. > The APIs of this module can be used only in the stage model. ## Usage Before calling any APIs in **ApplicationContext**, obtain an **ApplicationContext** instance through the **context** instance. ```ts let applicationContext = this.context.getApplicationContext(); ``` ## ApplicationContext.on(type: 'abilityLifecycle', callback: AbilityLifecycleCallback) on(type: 'abilityLifecycle', callback: AbilityLifecycleCallback): **number**; Registers a listener to monitor the ability lifecycle of the application. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------------------ | -------- | ---- | ------------------------------ | | type | 'abilityLifecycle' | Yes | Event type.| | callback | [AbilityLifecycleCallback](js-apis-app-ability-abilityLifecycleCallback.md) | Yes | Callback used to return the ID of the registered listener.| **Return value** | Type | Description | | ------ | ------------------------------ | | number | ID of the registered listener. The ID is incremented by 1 each time the listener is registered. When the ID exceeds 2^63-1, **-1** is returned.| **Example** ```ts import UIAbility from '@ohos.app.ability.UIAbility'; let lifecycleId; export default class EntryAbility extends UIAbility { onCreate() { console.log('MyAbility onCreate'); let AbilityLifecycleCallback = { onAbilityCreate(ability) { console.log('AbilityLifecycleCallback onAbilityCreate ability: ${ability}'); }, onWindowStageCreate(ability, windowStage) { console.log('AbilityLifecycleCallback onWindowStageCreate ability: ${ability}'); console.log('AbilityLifecycleCallback onWindowStageCreate windowStage: ${windowStage}'); }, onWindowStageActive(ability, windowStage) { console.log('AbilityLifecycleCallback onWindowStageActive ability: ${ability}'); console.log('AbilityLifecycleCallback onWindowStageActive windowStage: ${windowStage}'); }, onWindowStageInactive(ability, windowStage) { console.log('AbilityLifecycleCallback onWindowStageInactive ability: ${ability}'); console.log('AbilityLifecycleCallback onWindowStageInactive windowStage: ${windowStage}'); }, onWindowStageDestroy(ability, windowStage) { console.log('AbilityLifecycleCallback onWindowStageDestroy ability: ${ability}'); console.log('AbilityLifecycleCallback onWindowStageDestroy windowStage: ${windowStage}'); }, onAbilityDestroy(ability) { console.log('AbilityLifecycleCallback onAbilityDestroy ability: ${ability}'); }, onAbilityForeground(ability) { console.log('AbilityLifecycleCallback onAbilityForeground ability: ${ability}'); }, onAbilityBackground(ability) { console.log('AbilityLifecycleCallback onAbilityBackground ability: ${ability}'); }, onAbilityContinue(ability) { console.log('AbilityLifecycleCallback onAbilityContinue ability: ${ability}'); } } // 1. Obtain applicationContext through the context attribute. let applicationContext = this.context.getApplicationContext(); // 2. Use applicationContext to register a listener for the ability lifecycle in the application. lifecycleId = applicationContext.on('abilityLifecycle', AbilityLifecycleCallback); console.log('registerAbilityLifecycleCallback lifecycleId: ${lifecycleId)}'); } } ``` ## ApplicationContext.off(type: 'abilityLifecycle', callbackId: number, callback: AsyncCallback\) off(type: 'abilityLifecycle', callbackId: **number**, callback: AsyncCallback<**void**>): **void**; Deregisters the listener that monitors the ability lifecycle of the application. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------- | -------- | ---- | -------------------------- | | type | 'abilityLifecycle' | Yes | Event type.| | callbackId | number | Yes | ID of the listener to deregister.| | callback | AsyncCallback\ | Yes | Callback used to return the result. | **Example** ```ts import UIAbility from '@ohos.app.ability.UIAbility'; let lifecycleId; export default class EntryAbility extends UIAbility { onDestroy() { let applicationContext = this.context.getApplicationContext(); console.log('stage applicationContext: ${applicationContext}'); applicationContext.off('abilityLifecycle', lifecycleId, (error, data) => { if (error) { console.error('unregisterAbilityLifecycleCallback fail, err: ${JSON.stringify(error)}'); } else { console.log('unregisterAbilityLifecycleCallback success, data: ${JSON.stringify(data)}'); } }); } } ``` ## ApplicationContext.off(type: 'abilityLifecycle', callbackId: number) off(type: 'abilityLifecycle', callbackId: **number**): **void**; Deregisters the listener that monitors the ability lifecycle of the application. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------- | -------- | ---- | -------------------------- | | type | 'abilityLifecycle' | Yes | Event type.| | callbackId | number | Yes | ID of the listener to deregister.| **Example** ```ts import Ability from '@ohos.app.ability.UIAbility'; let lifecycleId; export default class MyAbility extends Ability { onDestroy() { let applicationContext = this.context.getApplicationContext(); console.log('stage applicationContext: ${applicationContext}'); applicationContext.off('abilityLifecycle', lifecycleId); } } ``` ## ApplicationContext.on(type: 'environment', callback: EnvironmentCallback) on(type: 'environment', callback: EnvironmentCallback): **number**; Registers a listener for system environment changes. This API uses an asynchronous callback to return the result. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------------------ | -------- | ---- | ------------------------------ | | type | 'environment' | Yes | Event type.| | callback | [EnvironmentCallback](js-apis-app-ability-environmentCallback.md) | Yes | Callback used to return the ID of the registered listener.| **Return value** | Type | Description | | ------ | ------------------------------ | | number | ID of the registered listener. The ID is incremented by 1 each time the listener is registered. When the ID exceeds 2^63-1, **-1** is returned.| **Example** ```ts import UIAbility from '@ohos.app.ability.UIAbility'; let callbackId; export default class EntryAbility extends UIAbility { onCreate() { console.log('MyAbility onCreate') globalThis.applicationContext = this.context.getApplicationContext(); let environmentCallback = { onConfigurationUpdated(config){ console.log('onConfigurationUpdated config: ${JSON.stringify(config)}'); }, onMemoryLevel(level){ console.log('onMemoryLevel level: ${level}'); } }; // 1. Obtain an applicationContext object. let applicationContext = globalThis.applicationContext; // 2. Use applicationContext to register a listener for system environment changes. callbackId = applicationContext.on('environment', environmentCallback); console.log('registerEnvironmentCallback callbackId: ${callbackId}'); } } ``` ## ApplicationContext.off(type: 'environment', callbackId: number, callback: AsyncCallback\) off(type: 'environment', callbackId: **number**, callback: AsyncCallback<**void**>): **void**; Deregisters the listener for system environment changes. This API uses an asynchronous callback to return the result. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------- | -------- | ---- | -------------------------- | | type | 'environment' | Yes | Event type.| | callbackId | number | Yes | ID of the listener to deregister. | | callback | AsyncCallback\ | Yes | Callback used to return the result. | **Example** ```ts import UIAbility from '@ohos.app.ability.UIAbility'; let callbackId; export default class EntryAbility extends UIAbility { onDestroy() { let applicationContext = this.context.getApplicationContext(); applicationContext.off('environment', callbackId, (error, data) => { if (error) { console.error('unregisterEnvironmentCallback fail, err: ${JSON.stringify(error)}'); } else { console.log('unregisterEnvironmentCallback success, data: ${JSON.stringify(data)}'); } }); } } ``` ## ApplicationContext.off(type: 'environment', callbackId: number) off(type: 'environment', callbackId: **number**, callback: AsyncCallback<**void**>): **void**; Deregisters the listener for system environment changes. This API uses an asynchronous callback to return the result. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Parameters** | Name | Type | Mandatory| Description | | ------------- | -------- | ---- | -------------------------- | | type | 'environment' | Yes | Event type.| | callbackId | number | Yes | ID of the listener to deregister. | **Example** ```ts import Ability from '@ohos.app.ability.UIAbility'; let callbackId; export default class MyAbility extends Ability { onDestroy() { let applicationContext = this.context.getApplicationContext(); applicationContext.off('environment', callbackId); } } ``` ## ApplicationContext.getRunningProcessInformation9+ getRunningProcessInformation(): Promise\>; Obtains information about the running processes. This API uses a promise to return the result. **Required permissions**: ohos.permission.GET_RUNNING_INFO **System capability**: SystemCapability.Ability.AbilityRuntime.Core **System API**: This is a system API and cannot be called by third-party applications. **Return value** | Type| Description| | -------- | -------- | | Promise\> | Promise used to return the API call result and the process running information. You can perform error handling or custom processing in this callback.| **Error codes** | ID| Error Message| | ------- | -------- | | 16000011 | The context does not exist. | | 16000050 | Internal error. | For details about the error codes, see [Ability Error Codes](../errorcodes/errorcode-ability.md). **Example** ```ts let applicationContext = this.context.getApplicationContext(); applicationContext.getRunningProcessInformation().then((data) => { console.log('The process running information is: ${JSON.stringify(data)}'); }).catch((error) => { console.error('error: ${JSON.stringify(error)}'); }); ``` ## ApplicationContext.getRunningProcessInformation9+ getRunningProcessInformation(callback: AsyncCallback\>): void; Obtains information about the running processes. This API uses an asynchronous callback to return the result. **Required permissions**: ohos.permission.GET_RUNNING_INFO **System capability**: SystemCapability.Ability.AbilityRuntime.Core **System API**: This is a system API and cannot be called by third-party applications. **Return value** | Type| Description| | -------- | -------- | |AsyncCallback\> | Callback used to return the API call result and the process running information. You can perform error handling or custom processing in this callback.| **Error codes** | ID| Error Message| | ------- | -------- | | 16000011 | The context does not exist. | | 16000050 | Internal error. | For details about the error codes, see [Ability Error Codes](../errorcodes/errorcode-ability.md). **Example** ```ts let applicationContext = this.context.getApplicationContext(); applicationContext.getRunningProcessInformation((err, data) => { if (err) { console.error('getRunningProcessInformation faile, err: ${JSON.stringify(err)}'); } else { console.log('The process running information is: ${JSON.stringify(data)}'); } }) ``` ## ApplicationContext.killAllProcesses9+ killAllProcesses(): Promise\; Kills all the processes where the application is located. This API uses a promise to return the result. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Return value** | Type| Description| | -------- | -------- | | Promise\ | Promise used to return the result.| **Error codes** | ID| Error Message| | ------- | -------- | | 16000011 | The context does not exist. | For details about the error codes, see [Ability Error Codes](../errorcodes/errorcode-ability.md). **Example** ```ts let applicationContext = this.context.getApplicationContext(); applicationContext.killAllProcesses(); ``` ## ApplicationContext.killAllProcesses9+ killAllProcesses(callback: AsyncCallback\); Kills all the processes where the application is located. This API uses an asynchronous callback to return the result. **System capability**: SystemCapability.Ability.AbilityRuntime.Core **Return value** | Type| Description| | -------- | -------- | |AsyncCallback\ | Callback used to return the result.| **Error codes** | ID| Error Message| | ------- | -------- | | 16000011 | The context does not exist. | For details about the error codes, see [Ability Error Codes](../errorcodes/errorcode-ability.md). **Example** ```ts let applicationContext = this.context.getApplicationContext(); applicationContext.killAllProcesses(error => { if (error) { console.error('killAllProcesses fail, error: ${JSON.stringify(error)}'); } }); ```