HarmonyOS 应用进入后台前，需要能刷新UI的回调

参考如下：

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

export default class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    try {
      windowStage.on('windowStageEvent', (data) => {
        console.info('Succeeded in enabling the listener for window stage event changes. Data: ' +
        JSON.stringify(data));

        // 根据事件状态类型选择进行相应的处理
        if (data == window.WindowStageEventType.SHOWN) {
          console.info('current window stage event is SHOWN');
          // 应用进入前台，默认为可交互状态
          // ...
        } else if (data == window.WindowStageEventType.HIDDEN) {
          console.info('current window stage event is HIDDEN');
          // 应用进入后台，默认为不可交互状态
          // ...
        } else if (data == window.WindowStageEventType.PAUSED) {
          console.info('current window stage event is PAUSED');
          // 前台应用进入多任务，转为不可交互状态
          // ...
        } else if (data == window.WindowStageEventType.RESUMED) {
          console.info('current window stage event is RESUMED');
          // 进入多任务后又继续返回前台时，恢复可交互状态
          // ...
        }

        // ...
      });
    } catch (exception) {
      console.error('Failed to enable the listener for window stage event changes. Cause:' +
      JSON.stringify(exception));
    }
  }
}

参考：https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/application-window-stage-V5