Android Clicks Twice to exit the program

Click the program twice in a row to exit the program. This is an interesting program function. Let's introduce my implementation method (You are welcome to give some suggestions ):
1. Set a long global variable firstTime = 0 in the Activity to record the time of the first press (unit: milliseconds );
2. Response to the onKeyUp event of the Activity:

@ Override
Public boolean onKeyUp (int keyCode, KeyEvent event ){
If (keyCode = KeyEvent. KEYCODE_BACK ){
Long secondTime = System. currentTimeMillis ();
If (secondTime-firstTime> 800) {// if the interval between two buttons is greater than 800 milliseconds, do not exit
Toast. makeText (MainActivity. this, "exit the program again ...",
Toast. LENGTH_SHORT). show ();
FirstTime = secondTime; // update firstTime
Return true;
} Else {
System. exit (0); // otherwise exit the program
}
}
Return super. onKeyUp (keyCode, event );
}
OK!