HarmonyOS 应用亮度获取第一次值错误，为-1

可以参考如下demo获取跟随系统的亮度数值以及设置窗口亮度后如何获取当前窗口亮度：

import { promptAction, router, window } from '@kit.ArkUI';
import settings from '@ohos.settings';
import { BusinessError } from '@ohos.base';


@Entry
@Component
export struct Index {


  @State windowClass: window.Window | undefined = undefined;

  /**
   * 获取跟随系统的亮度数值
   */
  getLightWithoutSetting(){
    let context = getContext(this);
    let value = settings.getValueSync(context, settings.display.SCREEN_BRIGHTNESS_STATUS, '10');
    console.log(`当前屏幕的亮度为： ${JSON.stringify(value)}`);


  }

  /**
   * 只有设置窗口亮度后再获取，亮度信息才不会是-1
   */
  getLight() {
    let brightness: number = 0.78;
    let windowStage: window.WindowStage | undefined = AppStorage.get('windowStage') as window.WindowStage
    windowStage.getMainWindow((err: BusinessError, data) => {
      const errCode: number = err.code;
      if (errCode) {
        console.error('Failed to obtain the main window. Cause: ' + JSON.stringify(err));
        return;
      }
      this.windowClass = data;
      this.windowClass.setWindowBrightness(brightness, (err: BusinessError) => {
        const errCode: number = err.code;
        if (errCode) {
          console.error('Failed to set the brightness. Cause: ' + JSON.stringify(err));
          return;
        }

        let screenLight = this.windowClass?.getWindowProperties().brightness
        console.info('Succeeded in setting the brightness.');
        console.info(`Succeeded in getting the light:${screenLight}`);
      });

    });
  }


  build() {
    Column({ space: 10 }) {

      Button('获取亮度').onClick(() => {
        this.getLightWithoutSetting()
      })

      Button('点击设置并获取亮度')
        .onClick(() => {
          this.getLight()
        })

    }.width('100%')
    .height("100%")
    .justifyContent(FlexAlign.Center)
  }
}

运行上述代码前需替换EntryAbility.ets文件中的onWindowStageCreate方法

//替换代码如下：
onWindowStageCreate(windowStage: window.WindowStage): void {

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

  windowStage.loadContent('pages/Index', (err) => {
  AppStorage.setOrCreate('windowStage',windowStage)
  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.');
});
}