来自服务的Android更新活动UI

Question

我有一个服务,一直在检查新的任务.如果有新任务,我想刷新活动UI以显示该信息.我确实找到了https://github.com/commonsguy/cw-andtutorials/tree/master/18-LocalService/这个例子.这是一个很好的approch？还有其他例子吗？

谢谢.

Answer 1

请参阅下面的原始答案 - 该模式运行良好,但最近我开始使用不同的服务/活动通信方法:

• 使用绑定服务,使Activity能够直接引用服务,从而允许直接调用它,而不是使用Intents.

• 使用RxJava执行异步操作.

• 如果即使没有运行Activity,服务也需要继续后台操作,也可以从Application类启动服务,以便在解除绑定时不会停止.

与startService()/ LocalBroadcast技术相比,我在这种方法中发现的优点是

• 不需要数据对象来实现Parcelable - 这对我来说尤其重要,因为我现在在Android和iOS之间共享代码(使用RoboVM)
• RxJava提供了固定(和跨平台)调度,以及顺序异步操作的简单组合.
• 这应该比使用LocalBroadcast更有效,尽管使用RxJava的开销可能超过这个.

一些示例代码.首先是服务:

public class AndroidBmService extends Service implements BmService {

    private static final int PRESSURE_RATE = 500000;   // microseconds between pressure updates
    private SensorManager sensorManager;
    private SensorEventListener pressureListener;
    private ObservableEmitter<Float> pressureObserver;
    private Observable<Float> pressureObservable;

    public class LocalBinder extends Binder {
        public AndroidBmService getService() {
            return AndroidBmService.this;
        }
    }

    private IBinder binder = new LocalBinder();

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        logMsg("Service bound");
        return binder;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return START_NOT_STICKY;
    }

    @Override
    public void onCreate() {
        super.onCreate();

        sensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
        Sensor pressureSensor = sensorManager.getDefaultSensor(Sensor.TYPE_PRESSURE);
        if(pressureSensor != null)
            sensorManager.registerListener(pressureListener = new SensorEventListener() {
                @Override
                public void onSensorChanged(SensorEvent event) {
                    if(pressureObserver != null) {
                        float lastPressure = event.values[0];
                        float lastPressureAltitude = (float)((1 - Math.pow(lastPressure / 1013.25, 0.190284)) * 145366.45);
                        pressureObserver.onNext(lastPressureAltitude);
                    }
                }

                @Override
                public void onAccuracyChanged(Sensor sensor, int accuracy) {

                }
            }, pressureSensor, PRESSURE_RATE);
    }

    @Override
    public Observable<Float> observePressure() {
        if(pressureObservable == null) {
            pressureObservable = Observable.create(emitter -> pressureObserver = emitter);
            pressureObservable = pressureObservable.share();
        }
         return pressureObservable;
    }

    @Override
    public void onDestroy() {
        if(pressureListener != null)
            sensorManager.unregisterListener(pressureListener);
    }
} 

以及绑定到服务并接收压力高度更新的活动:

public class TestActivity extends AppCompatActivity {

    private ContentTestBinding binding;
    private ServiceConnection serviceConnection;
    private AndroidBmService service;
    private Disposable disposable;

    @Override
    protected void onDestroy() {
        if(disposable != null)
            disposable.dispose();
        unbindService(serviceConnection);
        super.onDestroy();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this, R.layout.content_test);
        serviceConnection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
                logMsg("BlueMAX service bound");
                service = ((AndroidBmService.LocalBinder)iBinder).getService();
                disposable = service.observePressure()
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(altitude ->
                        binding.altitude.setText(
                            String.format(Locale.US,
                                "Pressure Altitude %d feet",
                                altitude.intValue())));
            }

            @Override
            public void onServiceDisconnected(ComponentName componentName) {
                logMsg("Service disconnected");
            }
        };
        bindService(new Intent(
            this, AndroidBmService.class),
            serviceConnection, BIND_AUTO_CREATE);
    }
}

此活动的布局是:

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    >
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.controlj.mfgtest.TestActivity">

        <TextView
            tools:text="Pressure"
            android:id="@+id/altitude"
            android:gravity="center_horizontal"
            android:layout_gravity="center_vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </LinearLayout>
</layout>

如果服务需要在后台运行而没有绑定的Activity,则可以在Application类中OnCreate()使用它Context#startService().

我的原始答案(自2013年起):

在您的服务中:(在下面的示例中使用COPA作为服务).

使用LocalBroadCastManager.在您的服务onCreate中,设置广播公司:

broadcaster = LocalBroadcastManager.getInstance(this);

当您想要通知UI时:

static final public String COPA_RESULT = "com.controlj.copame.backend.COPAService.REQUEST_PROCESSED";

static final public String COPA_MESSAGE = "com.controlj.copame.backend.COPAService.COPA_MSG";

public void sendResult(String message) {
    Intent intent = new Intent(COPA_RESULT);
    if(message != null)
        intent.putExtra(COPA_MESSAGE, message);
    broadcaster.sendBroadcast(intent);
}

在您的活动中:

在onCreate上创建一个监听器:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    super.setContentView(R.layout.copa);
    receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String s = intent.getStringExtra(COPAService.COPA_MESSAGE);
            // do something here.
        }
    };
}

并在onStart中注册:

@Override
protected void onStart() {
    super.onStart();
    LocalBroadcastManager.getInstance(this).registerReceiver((receiver), 
        new IntentFilter(COPAService.COPA_RESULT)
    );
}

@Override
protected void onStop() {
    LocalBroadcastManager.getInstance(this).unregisterReceiver(receiver);
    super.onStop();
}

Answer 2

对我来说最简单的解决方案是发送一个广播,在活动oncreate我注册并定义这样的广播(updateUIReciver被定义为一个类实例):

 IntentFilter filter = new IntentFilter();

 filter.addAction("com.hello.action"); 

 updateUIReciver = new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {
                //UI update here

            }
        };
 registerReceiver(updateUIReciver,filter);

从服务中你发送的意图如下:

Intent local = new Intent();

local.setAction("com.hello.action");

this.sendBroadcast(local);

不要忘记取消注册destroy中的活动恢复:

unregisterReceiver(updateUIReciver);

Answer 3

我将使用绑定服务来执行此操作并通过在我的活动中实现侦听器与其进行通信.因此,如果您的应用程序实现myServiceListener,您可以在绑定它之后将其注册为服务中的侦听器,从绑定服务调用listener.onUpdateUI并在那里更新您的UI!

Answer 4

我建议您查看专为Android量身定制的EventBus Otto.您的活动/ UI可以从服务中侦听在总线上发布的事件,并将其自身与后端分离.

Answer 5

克莱德的解决方案有效,但它是一个广播,我相信它不会比直接调用方法效率低.我可能会弄错,但我认为广播对于应用程序间通信来说意味着更多.

我假设您已经知道如何使用Activity绑定服务.我做了类似下面的代码来处理这类问题:

class MyService extends Service {
    MyFragment mMyFragment = null;
    MyFragment mMyOtherFragment = null;

    private void networkLoop() {
        ...

        //received new data for list.
        if(myFragment != null)
            myFragment.updateList();
        }

        ...

        //received new data for textView
        if(myFragment !=null)
            myFragment.updateText();

        ...

        //received new data for textView
        if(myOtherFragment !=null)
            myOtherFragment.updateSomething();

        ...
    }
}


class MyFragment extends Fragment {

    public void onResume() {
        super.onResume()
        //Assuming your activity bound to your service
        getActivity().mMyService.mMyFragment=this;
    }

    public void onPause() {
        super.onPause()
        //Assuming your activity bound to your service
        getActivity().mMyService.mMyFragment=null;
    }

    public void updateList() {
        runOnUiThread(new Runnable() {
            public void run() {
                //Update the list.
            }
        });
    }

    public void updateText() {
       //as above
    }
}

class MyOtherFragment extends Fragment {
             public void onResume() {
        super.onResume()
        //Assuming your activity bound to your service
        getActivity().mMyService.mMyOtherFragment=this;
    }

    public void onPause() {
        super.onPause()
        //Assuming your activity bound to your service
        getActivity().mMyService.mMyOtherFragment=null;
    }

    public void updateSomething() {//etc... }
}

我省略了线程安全,这是必不可少的.在检查和使用或更改服务上的片段引用时,请确保使用锁或类似的东西.

Answer 6

Callback from service to activity to update UI.
ResultReceiver receiver = new ResultReceiver(new Handler()) {
    protected void onReceiveResult(int resultCode, Bundle resultData) {
        //process results or update UI
    }
}

Intent instructionServiceIntent = new Intent(context, InstructionService.class);
instructionServiceIntent.putExtra("receiver", receiver);
context.startService(instructionServiceIntent);