在后台使用Service实现一个倒计时定时器

Question

我想在我的应用程序中做什么:1. 当用户打开应用程序时，他将能够看到一个已经运行的倒计时计时器。在那个例子中，我想在一个总是每秒更新的textview中显示倒计时数字。2. 用户将能够停止它。3.用户可以离开应用程序，但是当他回到应用程序UI时，倒计时应该继续并显示更新的时间。

所以基于以上几点，我明白我需要实现在后台工作的Service。我读过这个链接，但我的问题是与实施。我对如何实现这种方式感到很困惑。话虽如此，我也想不出在用户返回应用程序时在UI中显示时间的方法。我也看到了这个链接，但我不确定是否只实现CountDownTimer使它成为一个运行的服务。那么我应该如何继续并实施它呢?任何链接到特定的教程/代码是赞赏的。谢谢。

更新:到目前为止，我已经能够做到以下几点:MainActivity.java

public class MainActivity extends Activity {
Button btnStart,btnStop;
Intent serviceIntent;
TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btnStart = (Button) findViewById(R.id.btnStart);
    btnStop = (Button) findViewById(R.id.btnStop);
    tv = (TextView) findViewById(R.id.timeView);
    //final MyCounter timer = new MyCounter(100000,1000);
    //tv.setText("100"); 
    //timer.start();
    serviceIntent = new Intent(MainActivity.this,MyService.class);
    btnStart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            startService(serviceIntent);
        }
    });
    btnStop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            stopService(serviceIntent);
        }
    });
}
@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;
}

MyService.java:

public class MyService extends Service {
MyCounter timer;
@Override
public void onCreate() {
    // TODO Auto-generated method stub
    timer = new MyCounter(100000,1000);
    super.onCreate();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    // TODO Auto-generated method stub
    timer.start();
    return super.onStartCommand(intent, flags, startId);
}
private class MyCounter extends CountDownTimer{
    public MyCounter(long millisInFuture, long countDownInterval) {
        super(millisInFuture, countDownInterval);
    }
    @Override
    public void onFinish() {
        Toast.makeText(getApplicationContext(), "death", Toast.LENGTH_LONG).show();
        stopSelf();
    }
    @Override
    public void onTick(long millisUntilFinished) {
        Toast.makeText(getApplicationContext(), (millisUntilFinished/1000)+"", Toast.LENGTH_SHORT).show();
    }
}
@Override
public void onDestroy() {
    // TODO Auto-generated method stub
    timer.cancel();
    //stopSelf();
    super.onDestroy();
}
@Override
public IBinder onBind(Intent arg0) {
    // TODO Auto-generated method stub
    return null;
}
    }

问题是:1. 除了这个Toast，我不知道如何在MainActivity UI上显示倒计时。2. 当我按下停止键时，它不会停止计数

Answer 1

使用bindService(Intent service, ServiceConnection conn, int flag)来绑定你的倒计时服务，然后在你的服务中，返回包含计数的绑定器，在你的活动中，一个实例化的ServiceConnection对象可以处理绑定器。AIDL也可以做到这一点，建议先看看如何绑定服务，希望能帮到你。

演示

public class BindService extends Service{
private int count;
private boolean quit;
private MyBinder binder = new MyBinder();
// My Binder
public class MyBinder extends Binder
{
    public int getCount()
    {
        // get the counting status：count
        return count;
    }
}
@Override
public IBinder onBind(Intent intent)
{
    System.out.println("Service is Binded");
    // return the binder instance
    return binder;
}
@Override
public void onCreate()
{
    super.onCreate();
    System.out.println("Service is Created");
    // counting work
    new Thread()
    {
        @Override
        public void run()
        {
            while (!quit)
            {
                try
                {
                    Thread.sleep(1000);
                }
                catch (InterruptedException e)
                {
                }
                count++;
            }
        }
    }.start();      
}
// invoke when the service unbind
@Override
public boolean onUnbind(Intent intent)
{
    System.out.println("Service is Unbinded");
    return true;
}
@Override
public void onDestroy()
{
    super.onDestroy();
    this.quit = true;
    System.out.println("Service is Destroyed");
}
@Override
public void onRebind(Intent intent) 
{
    super.onRebind(intent);
    this.quit = true;
    System.out.println("Service is ReBinded");
}   

}

然后是活动

public class MainActivity extends Activity{
Button bind , unbind , getServiceStatus;
BindService.MyBinder binder;
// define a ServiceConnection object
private ServiceConnection conn = new ServiceConnection()
{
    // then the Activity connected with the Service, this will be called
    @Override
    public void onServiceConnected(ComponentName name
        , IBinder service)
    {
        System.out.println("--Service Connected--");
        // achieve MyBinder instance
        binder = (BindService.MyBinder) service;
    }
    // then the connection break off
    @Override
    public void onServiceDisconnected(ComponentName name)
    {
        System.out.println("--Service Disconnected--");         
    }
};
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    bind = (Button) findViewById(R.id.bind);
    unbind = (Button) findViewById(R.id.unbind);
    getServiceStatus = (Button) findViewById(R.id.getServiceStatus);
    final Intent intent = new Intent();
    intent.setAction("org.crazyit.service.BIND_SERVICE");       
    bind.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View source)
        {
            //bind Serivce
            bindService(intent , conn , Service.BIND_AUTO_CREATE);  
        }
    });
    unbind.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View source)
        {
            //unbind Serivce
            unbindService(conn);
        }
    }); 
    getServiceStatus.setOnClickListener(new OnClickListener()
    {
        @Override
        public void onClick(View source)
        {
            // Toast to show the conut value
            Toast.makeText(MainActivity.this
                , "Serivce's count value is：" + binder.getCount()
                , 4000)
                .show();
        }
    });
}}