android传说中的按两次返回键退出

在项目比较常用，现记录备忘，代码如下

private long exitTime;

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK
&& event.getAction() == KeyEvent.ACTION_DOWN) {


if ((System.currentTimeMillis() - exitTime) > 2000) // System.currentTimeMillis()无论何时调用，肯定大于2000
{
Toast toast = Toast.makeText(getApplicationContext(),
getResources().getString(R.string.press_again_exit),
Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER, 0, 0);
toast.show();
exitTime = System.currentTimeMillis();
} else {
finish();
System.exit(0);
}


return true;
}
return super.onKeyDown(keyCode, event);

}

本人新手，大神勿喷！