HarmonyOS 获取手机设备宽高

参考以下demo

import { BusinessError } from '@kit.BasicServicesKit';
import { display } from '@kit.ArkUI';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';

  aboutToAppear(): void {
    displayWidth()
  }
  build() {
    Column(){

    }
  }
}
function displayWidth ():number {

  let displayClass: Array<display.Display> =[];
  let promise: Promise<Array<display.Display>> = display.getAllDisplays();

  promise.then((data: Array<display.Display>) => {
    displayClass = data;
    console.info('Succeeded in obtaining all the display objects. Data: ' + JSON.stringify(data));
  }).catch((err: BusinessError) => {
    console.error('Failed to obtain all the display objects. Code: ${err.code}, message: ${err.message}');
  });
  for (let index = 0; index < displayClass.length; index++) {
    const displayClass3:display.Display = displayClass[index];
    console.log('width3:'+ displayClass3?.width.toString() )
  }

  let displayClass2: display.Display | null = display.getDefaultDisplaySync();
  console.log('width2:'+ displayClass2?.width.toString())
  return displayClass2?.width
}