再按一次退出程序

1 public boolean onKeyDown(int keyCode, KeyEvent event) {
 2 if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
 3 if ((System.currentTimeMillis() - exitTime) > 2000) {
 4 Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
 5 exitTime = System.currentTimeMillis();
 6 } else {
 7 finish();
 8 }
 9 }
10 return false;
11 }