android 按两次返回键退出

// 返回键

private long exitTime = 0;

?

@Override

public boolean onKeyDown(int keyCode, KeyEvent event) {

if (keyCode == event.KEYCODE_BACK) {

if ((System.currentTimeMillis() - exitTime) > 2000) {

Toast.makeText(getApplicationContext(), "再按一次退出程序",

Toast.LENGTH_SHORT).show();

exitTime = System.currentTimeMillis();

} else {

finish();

// System.exit(0);

}

return true;

}

return super.onKeyDown(keyCode, event);

}