Android 实现点击两次BACK键退出应用

package com.example.clickexittest; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; import android.view.KeyEvent; import android.widget.Toast; public class MainActivity extends
Activity { private static final String TAG = MainActivity_Exit.class.getSimpleName(); // 定义一个变量，来标识是否退出 private static boolean isExit = false; private static Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { super.handleMessage(msg);
isExit = false; } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK)
{ exit(); return true; } return super.onKeyDown(keyCode, event); } private void exit() { if (!isExit) { isExit = true; Toast.makeText(getApplicationContext(), "再按一次后退键退出程序", Toast.LENGTH_SHORT).show(); // 利用handler延迟发送更改状态信息 mHandler.sendEmptyMessageDelayed(0,
2000); } else { Log.e(TAG, "exit application"); this.finish(); } } }