AOA USB connection issue

Question

I have been working on making USB connection specified in the link here and successfully implemented it. Its working fine accept it is frequently getting disconnected. I got to know from this link and this link that there is a bug in android OS that there is no broadcast event of USB connection event. I have implemented a receiver for getting USB disconnecting event which is not too much important. Also I refer this link to create stable connection with USB i.e. start data communication after USB connection without any loss. This whole thing is working fine when there is single activity or single screen in application.

For multiple screen this connection thing is having problem i.e. connection is not stable and I have multiple screen in application in which I can receive data via USB in any activity at any time. So I have 2 question which I am seeking answers of with some code if possible

1. How can I make stable connection with device attached via serial USB in android over multiple screens
2. How to get rid of this frequent disconnection problem in the application over multiple screens

Any help would be greatful

EDIT:

I am adding my service which is responsible for communication with usb and starts a thread for continuous receiving data

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;

import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.content.Intent;
import android.hardware.usb.UsbManager;
import android.os.IBinder;
import arya.omnitalk.com.usb.R;
import arya.omnitalk.com.usb.constants.FileReadingWritingConstants;
import arya.omnitalk.com.usb.constants.GeneralConstant;
import arya.omnitalk.com.usb.constants.UsbDataWriterConstants;

import com.hoho.android.usbserial.driver.UsbSerialProber;

public class UsbCommunicationService extends Service{

    public static ArrayList<String> _dataArray = new ArrayList<String>();
    private Thread mCommunicationThread = null;

    private class ReadThread implements Runnable {
        @Override
        public void run() {

            while (mCommunicationThread!= null && !mCommunicationThread.isInterrupted()) {

                // Here I write code to parse data received via USB

                 }          
        }
    }

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

        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE); // Creating object of usb manager
        UsbDataWriterConstants.driver = UsbSerialProber.acquire(manager); // Acquiring usb channel

        if (UsbDataWriterConstants.driver != null) {
            try {
                UsbDataWriterConstants.driver.open();
            } catch (IOException e1) {
                e1.printStackTrace();
            }

            try {
                ReadThread mReadThread = new ReadThread();
                mCommunicationThread = new Thread(mReadThread);
                mCommunicationThread.start();
            } catch (SecurityException e) {
                DisplayError(R.string.error_security);
                DisplayError(R.string.error_security);
            }
        }

    }

    @Override
    public void onStart(Intent intent, int startId) {
        super.onStart(intent, startId);

    }

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

    @Override
    public void onDestroy() {
        if (mCommunicationThread != null)
            mCommunicationThread.interrupt();
        super.onDestroy();
    }


}

Answer 1

You probably have disconnections because your service is only a bound service. First activity starts, bind to the service, which will then starts. When you switch to another activity, the first one is stopped, so it unbind. At this point, the service is not bound anymore, so it is killed. Bound services are explained here: http://developer.android.com/guide/components/bound-services.html

What you need is probably to keep the service running as long as USB is connected. To achieve that, you need a "persistent" service, a started one, as described here: http://developer.android.com/guide/components/services.html You can start your service in the onCreate of the activity that received the CONNECTED event, using:

public class HomeActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        // ...
        Intent intent = new Intent(this, UsbCommunicationService.class);
        startService(intent);
        // ...
    }
}

The UsbCommunicationService will be started via this method (onStart() is deprecated):

public class UsbCommunicationService extends Service {
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        // TODO : connect to USB...

        // We want this service to continue running until it is explicitly
        // stopped, so return sticky.       
        return START_STICKY;
    }
}

Next, all your activities can "bind", "unbind" and "rebind" to this service that will survive. Don't forget to stop it on DISCONNECT event, using:

stopSelf(); // Will actually stop AFTER all clients unbind... 

Answer 2

Here is the code of my Activity beeing registered for my USB accessory.

    public class UsbAccessoryAttachedWorkaroundActivity extends Activity {

    /**
     * Used only to catch the USB_ACCESSORY_ATTACHED event, has it is not broadcasted to 
     * anything else than the activity with the right accessory_filter (no Service, nor Receiver...)
     * DETACHED event is broadcasted as other events. 
     */

     @Override
     public void onCreate(Bundle savedInstanceState) {
             super.onCreate(savedInstanceState);
             Intent intent = new Intent(this, UsbService.class);
             startService(intent);
             finish(); // <- die ASAP, without displaying anything.
     }
    }

This way you get all CONNECT events as the activity is not still alive => Android relaunch it each time accessory is discovered... My Service starts my HomeActivity only if nobody is bound to it. If someone is bound, it means that a UI is already present, thus I just notify my listeners that the USB connection is back...