@Override

public boolean onKeyDown(int keyCode, KeyEvent event) {

if (keyCode==KeyEvent.KEYCODE_BACK) {

exitBy2Click();

}

return false;

}

private static Boolean isExit = false;

private void exitBy2Click() {

Timer tExit = null;

if (isExit == false) {

isExit = true; // 准备退出

Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();

tExit = new Timer();

tExit.schedule(new TimerTask() {

@Override

public void run() {

isExit = false; // 取消退出

}

}, 2000); // 如果2秒钟内没有按下返回键，则启动定时器取消掉刚才执行的任务

} else {

AppManager.getAppManager().AppExit(this);

System.exit(0);

}

}