从Service类调用活动类方法

Question

我在SO中看过很多关于此的帖子,但无法从服务类调用一个活动方法的确切和最简单的方法.广播接收器只是选项吗？没有捷径 ？我只需要在Service类中准备好媒体播放器后在Activity类中调用以下方法.

活动类:

    public void updateProgress() {
    // set Progress bar values
    songProgressBar.setProgress(0);
    songProgressBar.setMax(100);
    // Updating progress bar
    updateProgressBar();
}

服务类:

   @Override
public IBinder onBind(Intent intent) {
    Log.d(this.getClass().getName(), "BIND");
    return musicBind;
}

@Override
public boolean onUnbind(Intent intent) {
    return false;
}
    @Override
public void onPrepared(MediaPlayer mp) {
    try {
        mp.start();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    }

           // updateProgress();// Need to call the Activity method here 
  }

Answer 1

定义服务将用于通信事件的接口:

public interface ServiceCallbacks {
    void doSomething();
} 

写下你的服务课程.您的活动将绑定到此服务,因此请按照此处显示的示例进行操作.另外,我们将添加一个方法来设置ServiceCallbacks.

public class MyService extends Service {
    // Binder given to clients
    private final IBinder binder = new LocalBinder();
    // Registered callbacks
    private ServiceCallbacks serviceCallbacks;


    // Class used for the client Binder.
    public class LocalBinder extends Binder {
        MyService getService() {
            // Return this instance of MyService so clients can call public methods
            return MyService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    public void setCallbacks(ServiceCallbacks callbacks) {
        serviceCallbacks = callbacks;
    }
}

按照相同的指南编写Activity类,同时使其实现ServiceCallbacks接口.从服务绑定/取消绑定时,您将通过调用setCallbacks服务来注册/取消注册它.

public class MyActivity extends Activity implements ServiceCallbacks {
    private MyService myService;
    private boolean bound = false;

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

    @Override
    protected void onStart() {
        super.onStart();
        // bind to Service
        Intent intent = new Intent(this, MyService.class);
        bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onStop() {
        super.onStop();
        // Unbind from service
        if (bound) {
            myService.setCallbacks(null); // unregister
            unbindService(serviceConnection);
            bound = false;
        }
    }

    /** Callbacks for service binding, passed to bindService() */
    private ServiceConnection serviceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            // cast the IBinder and get MyService instance
            LocalBinder binder = (LocalBinder) service;
            myService = binder.getService();
            bound = true;
            myService.setCallbacks(MyActivity.this); // register
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            bound = false;
        }
    };

    /* Defined by ServiceCallbacks interface */
    @Override
    public void doSomething() {
        ...
    }
}

现在,当您的服务想要与活动进行通信时,只需调用之前的一种接口方法即可.在你的服务内:

if (serviceCallbacks != null) { 
    serviceCallbacks.doSomething();
}

Answer 2

使用带服务的广播接收器从服务类更新视图.例如:

1. 在我的活动课上

   public class ServiceDemoActivity extends Activity {
   
       Intent intent;
       /** Called when the activity is first created. */
       @Override
       public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.main);
           final TextView notification = (TextView) findViewById(R.id.notification);
           if (CheckIfServiceIsRunning()) {
   
           } else {
               startService(new Intent(this, MyService.class));
           }
       }
   
       private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
           @Override
           public void onReceive(Context context, Intent intent) {
               updateDate(intent);
           }
       };
   
       private void updateDate(Intent intent) {
           String time = intent.getStringExtra("time");
           Toast.makeText(getApplicationContext(), "Yea!!! Service called", Toast.LENGTH_SHORT).show();
           TextView date = (TextView) findViewById(R.id.date);
           date.setText(time);
       }
   
       @Override
       public void onResume() {
           super.onResume();
           registerReceiver(broadcastReceiver, new IntentFilter(
                   MyService.BROADCAST_ACTION));
       }
   }
   

   在我的服务类中,我在几个时间间隔之后调用我的更新ui来更新我的UI.

   public class MyService extends Service {    
   
           public static final String
           BROADCAST_ACTION = "com.mukesh.service";    
           private final Handler handler = new Handler();
   
   
           @Override
           public void onCreate() {
   
               intent = new Intent(BROADCAST_ACTION);
           }
   
           @Override   
           public void onDestroy() {
   
               stopService(intent);
           }
   
           @Override
           public void onStart(Intent intent, int startid) {
               int i = 0;
               while (i <= 2) {
                   if (i > 1) {
                       i++;
                       this.onDestroy();
                   } else {
                       counter = i;
                       i++;
                       handler.removeCallbacks(sendUpdatesToUI);
                       handler.postDelayed(sendUpdatesToUI, 1 * 1000); // 1 sec
                   }
               }       
           }
   
           private Runnable sendUpdatesToUI = new Runnable() {
               public void run() {
                   DisplayLoggingInfo();           
                           handler.postDelayed(this, 7 * 1000); // 7 sec
               }
           };
   
           private void DisplayLoggingInfo() {  
               intent.putExtra("time", new Date().toLocaleString());
               intent.putExtra("counter", String.valueOf(counter));
               sendBroadcast(intent);
               stopService(intent);
           }
    }
   

有关完整代码,请查看此链接