How to get an android service return message from a phonegap plugin

Question

I am trying to make a plugin for Phonegap (Android) that allows my javascript to send and receive messages to / from a service. My exact problem is, that because the messages return asynchronous, I cannot send the PluginResult to the execute function of the plugin.

This is the plugin code:

public class ServiceClient_plugin extends Plugin {
    Messenger messenger_service=null;
    boolean connected_to_service=false;
    final Messenger messenger_receive = new Messenger(new IncomingHandler());

    @Override
    public PluginResult execute(String action, JSONArray data, String callbackId) {
        PluginResult result = null;

        try {
            if (action.toUpperCase().equals("CONNECT")) {
                result = ConnectService();
            } else if (action.toUpperCase().equals("DISCONNECT")) {
                result = DisconnectService();
            } else if (action.toUpperCase().equals("IS_CONNECTED")) {
                result = new PluginResult(Status.OK,connected_to_service);
            } else if (action.toUpperCase().equals("COMMAND")) {
                sendMSG (data.getString(0));
                result = new PluginResult(Status.OK);
            } else {
                result = new PluginResult(Status.INVALID_ACTION);
            }
        } catch(JSONException e) {
             result= new PluginResult(PluginResult.Status.JSON_EXCEPTION);
        }
        return result;
    }

    private PluginResult ConnectService() {
        doBindService();
        return new PluginResult(Status.OK);
    }
    private PluginResult DisconnectService() {
        doUnbindService();
        return new PluginResult(Status.OK);
    }

    class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MoMe_Service.MSG_COMMAND:
                Log.i("CLIENT","Received from service: " + msg.getData().getString("MSG"));
                break;
            default:
                super.handleMessage(msg);
        }
    }
}

private ServiceConnection service_connection = new ServiceConnection() {
    public void onServiceConnected(ComponentName className,  IBinder service) {
        messenger_service = new Messenger(service);
        connected_to_service=true;
        try {
            Message msg = Message.obtain(null,  My_Service.MSG_REGISTERED);
            msg.replyTo = messenger_receive;
            messenger_service.send(msg);
        } catch (RemoteException e) {
            // In this case the service has crashed before we could even
            // do anything with it; we can count on soon being
            // disconnected (and then reconnected if it can be restarted)
            // so there is no need to do anything here.
        }

    }

    public void onServiceDisconnected(ComponentName className) {
        // This is called when the connection with the service has been
        // unexpectedly disconnected -- that is, its process crashed.
        messenger_service = null;
        connected_to_service=false;
    }
};    

private void doBindService() {
    // Establish a connection with the service.  We use an explicit
    // class name because there is no reason to be able to let other
    // applications replace our component.
    this.ctx.bindService(new Intent(this.ctx, My_Service.class), service_connection, Context.BIND_AUTO_CREATE);
}

private void doUnbindService() {
    if (connected_to_service) {
        if (messenger_service != null) {
            try {
                Message msg = Message.obtain(null, My_Service.MSG_UNREGISTERED);
                msg.replyTo = messenger_receive;
                messenger_service.send(msg);
            } catch (RemoteException e) {
                // There is nothing special we need to do if the service
                // has crashed.
            }
        }

        // Detach our existing connection.
        this.ctx.unbindService(service_connection);
        connected_to_service = false;
    }
}

private void sendMSG (String message) {
    try {
        Message msg=Message.obtain(null, My_Service.MSG_COMMAND);
        Bundle msg_bundle=new Bundle();
        msg_bundle.putString("MSG", message);
        msg.setData(msg_bundle);
        messenger_service.send(msg);
    } catch (RemoteException e) {
        doUnbindService();
    }
}

}

From this plugin the real trouble comes with this part of code, which handles the return messages and the plugin return (which goes to the javascript):

    @Override
    public PluginResult execute(String action, JSONArray data, String callbackId) {
        PluginResult result = null;

        try {
            result = new PluginResult(Status.ok);
            }
        } catch(JSONException e) {
             result= new PluginResult(PluginResult.Status.JSON_EXCEPTION);
        }
        return result;
    }

    class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MoMe_Service.MSG_COMMAND:
                msg.getData().getString("MSG")); // THIS IS THE DATA I NEED RETURNED
                break;
            default:
                super.handleMessage(msg);
        }
      }
     }

The only solution I can think of, is storing the response in either a database or a variable and have the javascript do a setInterval to keep checking for changes. However I am not very fond of this solution. I would like to use some sort of callback function to let the javascript know the message has returned but I have no idea how. I would greatly appreciate any help and ideas.

Thank you, Vlad

Answer 1

This might be a late answer but I started to work with Cordova Plugin around 5 months ago and I just saw your question. Since you did not choose the correct answer I wanted to answer your question.

Assuming you have asynchronous process and you have a listener and methods, success and fail , lets call it onSuccess() and onFail() . As long as you send true with pluginResult.setKeepCallback(true) , the process will remain as unfinished, so you can send your plugin result data later on when you are done with background process. Here is an example take a look.

@Override
public boolean execute(String action, JSONArray data, String callbackId)  throws JSONException {
        if (action.equals("start")) {

              start();
        } else {
            PluginResult pluginResult = new PluginResult(PluginResult.Status.INVALID_ACTION);
            callbackContext.sendPluginResult(pluginResult);
            return false;
        }
}


    private boolean start() throws JSONException {

        MyClass.startProcess(new MyInterface() {

            @Override
            public void onSuccess(String data) {

                PluginResult result = new PluginResult(PluginResult.Status.OK, data);
                result.setKeepCallback(false);
                callbackContext.sendPluginResult(result);
            }

            @Override
            public void onFail() {

                PluginResult result = new PluginResult(PluginResult.Status.ERROR);
                result.setKeepCallback(false);
                callbackContext.sendPluginResult(result);
            }

        });

    PluginResult.Status status = PluginResult.Status.NO_RESULT;

    PluginResult pluginResult = new PluginResult(status);
    pluginResult.setKeepCallback(true);
    callbackContext.sendPluginResult(pluginResult);
    return true;

    }

Answer 2

The answer to my problem was actually in the the PluginResult object and success method. I've found a plugin that had to face the same problem in order to work, and from this code i was able to figure out my answer.This is a onPhoneStatusChange plugin, which can be found here !

The mystery lies in these lines:

PluginResult res = new PluginResult(PluginResult.Status.OK, obj);
res.setKeepCallback(true);
success(res, callbackId);

Answer 3

The generic solution to this problem is to have the service store the response into persistent storage (like a database) and then fire off a broadcast intent. Then just have a BroadcastReciever in your ServiceClient_plugin class listening for the broadcast. This way you woun't have to keep polling to see if the data has arrived yet.

Answer 4

You can send PluginResult using success() function like this:

public PluginResult execute(String action, JSONArray data, String callbackId) {}
private BroadcastReceiver Wifi_Receiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        MyClass.this.success(new PluginResult(PluginResult.Status.OK,"count"+count),callback);
    }
}

here callback is callbackId of execute() function