HarmonyOS 鸿蒙Next 添加折叠屏设备的折叠监听，折叠完成 需延迟（如50ms）才能获取当前状态的屏幕尺寸

刚打开应用时使用display.getDefaultDisplaySync()方法获取屏幕尺寸

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-display-V5#displaygetdefaultdisplaysync9

然后通过窗口的on('windowSizeChange')方法实现对窗口尺寸大小变化的监听：

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-window-V5#onwindowsizechange7

参考：

import { AbilityConstant, UIAbility, Want } from '[@kit](/user/kit).AbilityKit';
import { hilog } from '[@kit](/user/kit).PerformanceAnalysisKit';
import { window } from '[@kit](/user/kit).ArkUI';
import { BusinessError } from '[@kit](/user/kit).BasicServicesKit';

export default class EntryAbility extends UIAbility {
 onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');
 }

 onDestroy(): void {
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onDestroy');
 }

 onWindowStageCreate(windowStage: window.WindowStage): void {
   // Main window is created, set main page for this ability
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');
   let windowClass: window.Window | undefined = undefined;
   try {
     window.getLastWindow(this.context, (err: BusinessError, data) => {
       const errCode: number = err.code;
       if (errCode) {
         console.error('Failed to obtain the top window. Cause: ' + JSON.stringify(err));
         return;
       }
       windowClass = data;
       try {
         windowClass.on('windowSizeChange', (data) => {
           AppStorage.setOrCreate('width', data.width);
           AppStorage.setOrCreate('height', data.height);
         });
       } catch (exception) {
         console.error('Failed to enable the listener for window size changes. Cause: ' + JSON.stringify(exception));
       }
       console.info('Succeeded in obtaining the top window. Data: ' + JSON.stringify(data));
     });
   } catch (exception) {
     console.error('Failed to obtain the top window. Cause: ' + JSON.stringify(exception));
   }
   windowStage.loadContent('pages/Index', (err) => {
     if (err.code) {
       hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');
       return;
     }
     hilog.info(0x0000, 'testTag', 'Succeeded in loading the content.');
   });
 }

 onWindowStageDestroy(): void {
   // Main window is destroyed, release UI related resources
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageDestroy');
 }

 onForeground(): void {
   // Ability has brought to foreground
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onForeground');
 }

 onBackground(): void {
   // Ability has back to background
   hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onBackground');
 }
}

import display from '[@ohos](/user/ohos).display';
[@Entry](/user/Entry)
[@Component](/user/Component)
struct Index {
 [@StorageLink](/user/StorageLink)('width') width1: number = 0;
 [@StorageLink](/user/StorageLink)('height') height1: number = 0;

 aboutToAppear(): void {
   let displayClass: display.Display | null = null;
   displayClass = display.getDefaultDisplaySync();
   this.width1 = displayClass.width;
   this.height1 = displayClass.height;
 }

 build() {
   Column() {
     Text(this.width1.toString())
       .fontSize(50)
       .fontWeight(FontWeight.Bold)
     Text(this.height1.toString())
       .fontSize(50)
       .fontWeight(FontWeight.Bold)
   }
   .height('100%')
   .width('100%')
 }
}