Question

In one of my Apps I do have a FileCache in a library project. The App itself has a Service waiting for notfications when the FileCache in the library has cached a new file.

The library is an Android library project and included in the App.

What’s the best way to send a notification from the library to the App Service?

• Sending a Broadcast needs to know the Receiver in the Service. This is not possible from within the library project.

• Calling a function within the Service from the library code isn’t possible neither.

Here’s a code skeleton:

// This is in the App
public class MyService extends Service implements OnBufferingUpdateListener, OnCompletionListener, OnErrorListener, OnInfoListener, OnPreparedListener {

    public class MyBroadcastReceiver extends BroadcastReceiver {

        public static final String BROADCASTRECEIVER = "xx.yyy.zzzzz.MyService.MyBroadcastReceiver";

        @Override
        public void onReceive(final Context context, final Intent intent) {
        }
    }
}

// This is in a library project that's included in the App
public class FileCache {

    private void doThread() {
        final Handler handler = new Handler() {

            @Override
            public void handleMessage(final Message message) {

                try {
                    if (processed.size() > 0) {
                        //TODO: Notification to Service
                        processed.clear();
                    }
                } catch (NullPointerException nullPointerException) {
                    //TODO:
                }

                if (queue.size() > 0) {
                    doThread();
                } else {
                    running = false;
                }
            }
        };

        new Thread() {

            @Override
            public void run() {
                for (Map.Entry<String, QueueElement> entry : queue.entrySet()) {
                    QueueElement element = entry.getValue();
                    if (element != null) {
                        File file = fetch(element.url);
                        if (file != null) {
                            ProcessedElement processedElement = new ProcessedElement();
                            processedElement.file = file; 
                            processedElement.url = element.url; 
                            processed.put(entry.getKey(), processedElement);
                        }
                    }

                    deleteFromQueue(entry.getKey());
                }

                handler.sendEmptyMessage(0);
            }
        }.start();
    }
}

Answer 1

Sending a Broadcast needs to know the Receiver in the Service. This is not possible from within the library project.

Sure it is. Have the client of your library project supply to the library enough information, via parameters on some method, to either:

• Identify the service (e.g., service Class object), in which case you use startService() to send a command to the service, or

• Identify the BroadcastReceiver (e.g., the action string used by its IntentFilter), in which case you use sendBroadcast()