android 按两次返回退出

把下面代码复制进Activity类中就可以了；

 

private static Boolean isExit = false;

private static Boolean hasTask = false;

Timer tExit = new Timer();

TimerTask task = new TimerTask() {

@Override

public void run() {

isExit = false;

hasTask = true;

}

};

 

public boolean onKeyDown(int keyCode, KeyEvent event) {

if (keyCode == KeyEvent.KEYCODE_BACK) {

if (isExit == false) {

isExit = true;

Toast.makeText(this, "press once again to exit", Toast.LENGTH_SHORT).show();

if (!hasTask) {

tExit.schedule(task, 2000);

} else {

finish();

System.exit(0);

}

}

}

return false;

}