Click twice to exit the application system to achieve the return key

Implement application indispensable event, two clicks to achieve the return key to exit the application, here to write two methods are very simple, first began Method 1:

Define a time interval of two clicks back button

// first click and the second click time interval of 
private long exitTime;

 Then click the back key to achieve events

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0){
            exit();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

    private void exit(){
        if((System.currentTimeMillis() - exitTime) > 2000){
            Toast.makeText(this, "再次点击退出应用", Toast.LENGTH_SHORT).show();
            exitTime = System.currentTimeMillis();
        }else{
            finish();
            System.exit(0);
        }
    }

 

Next implementation 2, Handler delay by sending messages reach the exit status change application:

1  // definition of a variable is determined whether to exit 
2      Private Boolean = isExit to false ;
 . 3  
. 4      Handler Handler = new new Handler () {
 . 5          @Override
 . 6          public  void the handleMessage (@NonNull the Message MSG) {
 . 7              super.handleMessage (MSG);
 . 8              isExit = to false ;
 . 9          }
 10      };

Events then click on the system to achieve the return key (note method exit the judgment is "isExit!"):

 1 @Override
 2     public boolean onKeyDown(int keyCode, KeyEvent event) {
 3         if(keyCode == KeyEvent.KEYCODE_BACK){
 4             exit();
 5             return false;
 6         }
 7         return super.onKeyDown(keyCode, event);
 8     }
 9 
10     private void exit(){
11         if(!isExit){
12             isExit = true;
13             Toast.makeText ( the this , " Click again to exit the application " , Toast.LENGTH_SHORT) the .Show ();
 14              // send status change message by the delay Handler 
15              handler.sendEmptyMessageDelayed ( 0 , 2000 );
 16          } the else {
 . 17              Finish ( );
 18 is              System.exit ( 0 );
 . 19          }
 20 is      }