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uiability-lifecycle.md 11.79 KB
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Luobniz 提交于 17天前 . MultiAppMode

UIAbility组件生命周期

概述

当用户在执行应用启动、应用前后台切换、应用退出等操作时,系统会触发相关应用组件的生命周期回调。其中,UIAbility组件的核心生命周期回调包括onCreateonForegroundonBackgroundonDestroy。作为一种包含UI的应用组件,UIAbility的生命周期不可避免地与WindowStage的生命周期存在关联关系。

UIAbility的生命周期示意图如下所示。

UIAbility-Life-Cycle

以UIAbility实例的冷启动为例说明:

  1. 当用户启动一个UIAbility时,系统首先触发onCreate()回调告知应用该UIAbility正在被启动。紧接着,系统触发onForeground()回调将UIAbility切换到与用户交互的前台状态。

  2. 当用户跳转到其他应用时,系统会触发onBackground()回调将UIAbility切换到后台状态。

  3. 当用户退出UIAbility时,系统会触发onDestroy()回调告知应用该UIAbility将被销毁。

生命周期回调

说明:

  • 生命周期回调是在应用主线程执行,为了确保应用性能,建议在生命周期回调中,仅执行必要的轻量级操作。对于耗时任务,推荐采用异步处理或交由子线程执行,避免阻塞主线程。
  • 如果需要感知UIAbility生命周期变化,开发者可以使用ApplicationContext注册接口监听UIAbility生命周期变化。详见订阅进程内UIAbility生命周期变化

onCreate()

在首次创建UIAbility实例时,系统触发onCreate()回调。开发者可以在该回调中执行UIAbility整个生命周期中仅发生一次的启动逻辑。

import { AbilityConstant, UIAbility, Want } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    // 执行UIAbility整个生命周期中仅发生一次的业务逻辑
  }
  // ...
}

onWindowStageCreate()

UIAbility实例创建完成之后,在进入前台之前,系统会创建一个WindowStage。WindowStage创建完成后会进入onWindowStageCreate()回调,开发者可以在该回调中进行UI加载、WindowStage的事件订阅。

在onWindowStageCreate()回调中通过loadContent()方法设置应用要加载的页面,并根据需要调用on('windowStageEvent')方法订阅WindowStage的事件(获焦/失焦、切到前台/切到后台、前台可交互/前台不可交互)。

说明:

import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { hilog } from '@kit.PerformanceAnalysisKit';

const DOMAIN_NUMBER: number = 0xFF00;

export default class EntryAbility extends UIAbility {
  // ...
  onWindowStageCreate(windowStage: window.WindowStage): void {
    // 设置WindowStage的事件订阅(获焦/失焦、切到前台/切到后台、前台可交互/前台不可交互)
    try {
      windowStage.on('windowStageEvent', (data) => {
        let stageEventType: window.WindowStageEventType = data;
        switch (stageEventType) {
          case window.WindowStageEventType.SHOWN: // 切到前台
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage foreground.`);
            break;
          case window.WindowStageEventType.ACTIVE: // 获焦状态
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage active.`);
            break;
          case window.WindowStageEventType.INACTIVE: // 失焦状态
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage inactive.`);
            break;
          case window.WindowStageEventType.HIDDEN: // 切到后台
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage background.`);
            break;
          case window.WindowStageEventType.RESUMED: // 前台可交互状态
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage resumed.`);
            break;
          case window.WindowStageEventType.PAUSED: // 前台不可交互状态
            hilog.info(DOMAIN_NUMBER, 'testTag', `windowStage paused.`);
            break;
          default:
            break;
        }
      });
    } catch (exception) {
      hilog.error(DOMAIN_NUMBER, 'testTag',
        `Failed to enable the listener for window stage event changes. Cause: ${JSON.stringify(exception)}`);
    }
    hilog.info(DOMAIN_NUMBER, 'testTag', `%{public}s`, `Ability onWindowStageCreate`);
    // 设置UI加载
    windowStage.loadContent('pages/Index', (err, data) => {
      // ...
    });
  }
}

onForeground()

UIAbility切换至前台时且UIAbility的UI可见之前,系统触发onForeground回调。开发者可以在该回调中申请系统需要的资源,或者重新申请在onBackground()中释放的资源。系统回调该方法后,UIAbility实例进入前台状态,即UIAbility实例可以与用户交互的状态。UIAbility实例会一直处于这个状态,直到被某些动作打断(例如屏幕关闭、用户跳转到其他UIAbility)。

例如,应用在使用过程中需要使用用户定位时,假设应用已获得用户的定位权限授权。在UI显示之前,开发者可以在onForeground()回调中开启定位功能,从而获取到当前的位置信息。

import { UIAbility } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  // ...

  onForeground(): void {
    // 申请系统需要的资源,或者重新申请在onBackground()中释放的资源
  }
  // ...
}

onBackground()

UIAbility的UI完全不可见之后,系统触发onBackground回调,回调后触发UIAbility实例切换至后台状态。开发者可以在该回调中释放UI不可见时的无用资源,例如停止定位功能,以节省系统的资源消耗。

onBackground()执行时间较短,无法提供足够的时间做一些耗时动作。请勿在该方法中执行保存用户数据或执行数据库事务等耗时操作。

import { UIAbility } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  // ...

  onBackground(): void {
    // 释放UI不可见时无用的资源
  }
  // ...
}

onWindowStageWillDestroy()

UIAbility实例销毁之前,系统触发onWindowStageWillDestroy()回调。该回调在WindowStage销毁前执行,此时WindowStage可以使用。开发者可以在该回调用释放通过WindowStage获取的资源、注销WindowStage事件订阅等。

import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';

const DOMAIN_NUMBER: number = 0xFF00;

export default class EntryAbility extends UIAbility {
  windowStage: window.WindowStage | undefined = undefined;
  // ...
  onWindowStageCreate(windowStage: window.WindowStage): void {
    this.windowStage = windowStage;
    // ...
  }

  onWindowStageWillDestroy(windowStage: window.WindowStage) {
    // 释放通过windowStage对象获取的资源
    // 在onWindowStageWillDestroy()中注销WindowStage事件订阅(获焦/失焦、切到前台/切到后台、前台可交互/前台不可交互)
    try {
      if (this.windowStage) {
        this.windowStage.off('windowStageEvent');
      }
    } catch (err) {
      let code = (err as BusinessError).code;
      let message = (err as BusinessError).message;
      hilog.error(DOMAIN_NUMBER, 'testTag', `Failed to disable the listener for windowStageEvent. Code is ${code}, message is ${message}`);
    }
  }
}

onWindowStageDestroy()

UIAbility实例销毁之前,系统触发onWindowStageDestroy()回调,开发者可以在该回调中释放UI资源。该回调在WindowStage销毁后执行,此时WindowStage不可以使用。

import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';

export default class EntryAbility extends UIAbility {
  // ...

  onWindowStageCreate(windowStage: window.WindowStage): void {
    // 加载UI资源
  }

  onWindowStageDestroy() {
    // 释放UI资源
  }
}

onDestroy()

UIAbility实例销毁之前,系统触发onDestroy回调。该回调是UIAbility接收到的最后一个生命周期回调,开发者可以在onDestroy()回调中进行系统资源的释放、数据的保存等操作。

例如,调用terminateSelf()方法停止当前UIAbility实例,执行onDestroy()回调,并完成UIAbility实例的销毁。

再比如,用户使用最近任务列表关闭该UIAbility实例,执行onDestroy()回调,并完成UIAbility实例的销毁。
import { UIAbility } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  // ...

  onDestroy() {
    // 系统资源的释放、数据的保存等
  }
}

onNewWant()

当应用的UIAbility实例已创建,再次调用方法启动该UIAbility实例时,系统触发该UIAbility的onNewWant()回调。开发者可以在该回调中更新要加载的资源和数据等,用于后续的UI展示。

import { AbilityConstant, UIAbility, Want } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  // ...

  onNewWant(want: Want, launchParam: AbilityConstant.LaunchParam) {
    // 更新资源、数据
  }
}

相关实例

针对UIAbility生命周期,有以下相关实例可供参考:

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