HarmonyOS如何监听到应用从前台退到应用切换选择页

import { UIAbility } from '@kit.AbilityKit'; 
import { hilog } from '@kit.PerformanceAnalysisKit'; 
import { window } from '@kit.ArkUI'; 
export default class EntryAbility extends UIAbility { 
  onWindowStageCreate(windowStage: window.WindowStage): void { 
    // Main window is created, set main page for this ability 
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate'); 
 
    windowStage.loadContent("pages/Index", (err, data) => { 
      if (err.code) { 
        hilog.error(0x0000, "testTag", "Failed to load the content. Cause: %{public}s", JSON.stringify(err) ?? ''); 
        return; 
      } 
      windowStage.on('windowStageEvent', (data) => { 
        if (data == window.WindowStageEventType.RESUMED) { 
          //前台 
          console.log('App is in Foreground') 
        } 
        else if(data == window.WindowStageEventType.PAUSED){ 
          //后台 
          console.log('App is in Background') 
        } 
      }) 
      hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? ''); 
    }); 
  } 
}
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