js-apis-application-applicationContext.md

# ApplicationContext

> **说明：**
> 
> 本模块首批接口从API version 9开始支持。后续版本的新增接口，采用上角标单独标记接口的起始版本。  
> 本模块接口仅可在Stage模型下使用。

提供开发者应用级别的的上下文，提供注册及取消注册应用内组件生命周期的监听接口。

## 导入模块

```
import Ability from '@ohos.application.Ability';
```

## 使用说明

在使用ApplicationContext的功能前，需要通过context的实例获取。

```js
let applicationContext = this.context.getApplicationContext();
```


## ApplicationContext.registerAbilityLifecycleCallback

registerAbilityLifecycleCallback(callback: AbilityLifecycleCallback): **number**;

注册监听应用内生命周期

**系统能力**：SystemCapability.Ability.AbilityRuntime.Core

**参数：**

| 参数名                   | 类型     | 必填 | 说明                           |
| ------------------------ | -------- | ---- | ------------------------------ |
| [AbilityLifecycleCallback](js-apis-application-abilityLifecycleCallback.md) | callback | 是   | 回调方法，返回注册监听事件的id |

**返回值：**

| 类型   | 说明                           |
| ------ | ------------------------------ |
| number | 返回的此次注册监听生命周期的id（每次注册该id会自增+1，当超过监听上限数量2^63-1时，返回-1）|


## ApplicationContext.unregisterAbilityLifecycleCallback

unregisterAbilityLifecycleCallback(callbackId: **number**,  callback: AsyncCallback<**void**>): **void**;

取消监听应用内生命周期

**系统能力**：SystemCapability.Ability.AbilityRuntime.Core

**参数：**

| 参数名        | 类型     | 必填 | 说明                       |
| ------------- | -------- | ---- | -------------------------- |
| callbackId    | number   | 是   | 注册监听应用内生命周期的id |
| AsyncCallback | callback | 是   | 回调方法                   |

**示例：**

  ```js
  import AbilityStage from "@ohos.application.AbilityStage";

  var lifecycleid;

  export default class MyAbilityStage extends AbilityStage {
      onCreate() {
          console.log("MyAbilityStage onCreate")
          let AbilityLifecycleCallback  =  {
              onAbilityCreate(ability){
                  console.log("AbilityLifecycleCallback onAbilityCreate ability:" + JSON.stringify(ability));        
              },
              onAbilityWindowStageCreate(ability){
                  console.log("AbilityLifecycleCallback onAbilityWindowStageCreate ability:" + JSON.stringify(ability));           
              },
              onAbilityWindowStageDestroy(ability){
                  console.log("AbilityLifecycleCallback onAbilityWindowStageDestroy ability:" + JSON.stringify(ability));
              },
              onAbilityDestroy(ability){
                  console.log("AbilityLifecycleCallback onAbilityDestroy ability:" + JSON.stringify(ability));             
              },
              onAbilityForeground(ability){
                  console.log("AbilityLifecycleCallback onAbilityForeground ability:" + JSON.stringify(ability));             
              },
              onAbilityBackground(ability){
                  console.log("AbilityLifecycleCallback onAbilityBackground ability:" + JSON.stringify(ability));              
              },
              onAbilityContinue(ability){
                  console.log("AbilityLifecycleCallback onAbilityContinue ability:" + JSON.stringify(ability));
              }
          }
          // 1.通过context属性获取applicationContext
          let applicationContext = this.context.getApplicationContext();
          // 2.通过applicationContext注册监听应用内生命周期
          lifecycleid = applicationContext.registerAbilityLifecycleCallback(AbilityLifecycleCallback);
          console.log("registerAbilityLifecycleCallback number: " + JSON.stringify(lifecycleid));       
      }
      onDestroy() {
          let applicationContext = this.context.getApplicationContext();
          applicationContext.unregisterAbilityLifecycleCallback(lifecycleid, (error, data) => {
          console.log("unregisterAbilityLifecycleCallback success, err: " + JSON.stringify(error));
          });
      }
  }
  ```