Android 单击两次返回键退出程序

Drop_out.java

<span style="font-size:14px;">package com.test.twiceexit;

import java.util.Timer;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;
import android.view.Menu;
import android.widget.Toast;


public class MainActivity extends Activity {
	private static Boolean isQuit = false;
	private long mExitTime = 0;

	Timer timer = new Timer();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	/**************************************************
	 * 						First
	 * ************************************************/
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			if (isQuit == false) {
				isQuit = true;
				Toast.makeText(getBaseContext(), "再按一次返回键退出程序",
						Toast.LENGTH_SHORT).show();
				TimerTask task = null;
				task = new TimerTask() {
					public void run() {
						isQuit = false;
					}
				};
				timer.schedule(task, 2000);
			} else {
				finish();
				System.exit(0);
			}
		}
		return false;
	}

	/**************************************************
	 * 						Second
	 * ************************************************/
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			if ((System.currentTimeMillis() - mExitTime) > 2000) {//
				// 如果两次按键时间间隔大于2000毫秒，则不退出
				Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
				mExitTime = System.currentTimeMillis();// 更新mExitTime
			} else {
				System.exit(0);// 否则退出程序
			}
			return true;
		}
		return super.onKeyDown(keyCode, event);

	}

	/**************************************************
	 * 						Third
	 * ************************************************/
	Handler mHandler = new Handler() {
		@Override
		public void handleMessage(Message msg) {
			super.handleMessage(msg);
			isQuit = false;
		}
	};

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			if (!isQuit) {
				isQuit = true;
				Toast.makeText(getApplicationContext(), "再按一次退出程序",
						Toast.LENGTH_SHORT).show();
				// 利用handler延迟发送更改状态信息
				mHandler.sendEmptyMessageDelayed(0, 2000);
			} else {
				finish();
				System.exit(0);
			}
		}
		return false;
	}
}
</span>