[harmonyos] [ark UI] how does harmonyos ETS language realize double clicking the return key to exit

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【Harmony OS】【ARK UI】Date Basic operation

Custom component lifecycle callback function

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Ideas ：

Define a global variable , Judge the difference between the click time and the last click time , If more than 2 Second prompt ‘ Press again to exit the program ’ word , Less than 2 Seconds to exit the application , The code is as follows

import prompt from '@system.prompt';
import app from '@system.app'
@Entry
@Component
struct Index {
  //todo  Define global variables 
  @State exitTime: number= 0;

  private onBackPress() {
    this.ExitApp();
    return true;
  }

  public ExitApp() {
    //todo  Judge the difference between the click time and the last click time , If more than 5 Second prompt ‘ Press again to exit the program ’ word 
    if ((new Date().getTime() - this.exitTime) > 5000) {
      prompt.showToast({
        message: ' Press again to exit the program ',
        duration: 2000,
      });
      this.exitTime = new Date().getTime();
    } else {
      //todo  Less than 5 Seconds to exit the application 
      app.terminate();
    }
  }

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Text(' Double click to return to app sign out ')
        .fontSize(40)
        .height(200)
        .width("100%")
        .textAlign(TextAlign.Center)
        .fontWeight(FontWeight.Bold)
    }
    .width('100%')
    .height('100%')
  }
}

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