Android Bluetooth connection with Serial Port Device

Question

I have used BluetoothChatService class from BluetoothChat example program for bluetooth connection. I have modified it like

private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

to connect it to a Serial Port Device.

My sample test android devices are NexusOne, HTC Desire, LG Optimus, Motorola Droid.

Whenever I use my application to connect it to a Hardware it connects and disconnects appropriately using NexusOne. But when using other android devices sometime they connect , sometimes even after trying 100s of times it doesn't connect. And sometimes when i disconnect , the application disconnects but the bluetooth light on the hardware is ON, indicating the connection is still ON . I am wondering if its my coding error, or hardware error, or Android OS bluetooth library error. I haven't face this issue with NexusOne. I haven't been able to pinpoint the exact location as to where the issue lies.

Can someone point me what could be the possible course of action I should take to solve this issue ?

---

Code that gives "Unable to connect device" Toast Message

/**

 * Constructor. Prepares a new BluetoothChat session.

 * @param context  The UI Activity Context

 * @param handler  A Handler to send messages back to the UI Activity

 */


public BluetoothChatService(Context context, Handler handler) {
    mAdapter = BluetoothAdapter.getDefaultAdapter();
    mState = STATE_NONE;
    mHandler = handler;
}

/**
 * Set the current state of the chat connection
 * @param state  An integer defining the current connection state
 */
private synchronized void setState(int state) {
    if (D) Log.d(TAG, "setState() " + mState + " -> " + state);
    mState = state;

    // Give the new state to the Handler so the UI Activity can update
    mHandler.obtainMessage(BluetoothChat.MESSAGE_STATE_CHANGE, state, -1).sendToTarget();
}

/**
 * Return the current connection state. */
public synchronized int getState() {
    return mState;
}

/**
 * Start the chat service. Specifically start AcceptThread to begin a
 * session in listening (server) mode. Called by the Activity onResume() */
public synchronized void start() {
    if (D) Log.d(TAG, "start");

    // Cancel any thread attempting to make a connection
    if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}

    // Cancel any thread currently running a connection
    if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}

    setState(STATE_LISTEN);

    // Start the thread to listen on a BluetoothServerSocket
    if (mSecureAcceptThread == null) {
        mSecureAcceptThread = new AcceptThread(true);
        mSecureAcceptThread.start();
    }
    if (mInsecureAcceptThread == null) {
        mInsecureAcceptThread = new AcceptThread(false);
        mInsecureAcceptThread.start();
    }
}

/**
 * Start the ConnectThread to initiate a connection to a remote device.
 * @param device  The BluetoothDevice to connect
 * @param secure Socket Security type - Secure (true) , Insecure (false)
 */
public synchronized void connect(BluetoothDevice device, boolean secure) {
    if (D) Log.d(TAG, "connect to: " + device);

    // Cancel any thread attempting to make a connection
    if (mState == STATE_CONNECTING) {
        if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
    }

    // Cancel any thread currently running a connection
    if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}

    // Start the thread to connect with the given device
    mConnectThread = new ConnectThread(device, secure);
    mConnectThread.start();
    setState(STATE_CONNECTING);
}

/**
 * Start the ConnectedThread to begin managing a Bluetooth connection
 * @param socket  The BluetoothSocket on which the connection was made
 * @param device  The BluetoothDevice that has been connected
 */
public synchronized void connected(BluetoothSocket socket, BluetoothDevice
        device, final String socketType) {
    if (D) Log.d(TAG, "connected, Socket Type:" + socketType);

    // Cancel the thread that completed the connection
    if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}

    // Cancel any thread currently running a connection
    if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}

    // Cancel the accept thread because we only want to connect to one device
    if (mSecureAcceptThread != null) {
        mSecureAcceptThread.cancel();
        mSecureAcceptThread = null;
    }
    if (mInsecureAcceptThread != null) {
        mInsecureAcceptThread.cancel();
        mInsecureAcceptThread = null;
    }

    // Start the thread to manage the connection and perform transmissions
    mConnectedThread = new ConnectedThread(socket, socketType);
    mConnectedThread.start();

    // Send the name of the connected device back to the UI Activity
    Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_DEVICE_NAME);
    Bundle bundle = new Bundle();
    bundle.putString(BluetoothChat.DEVICE_NAME, device.getName());
    msg.setData(bundle);
    mHandler.sendMessage(msg);

    setState(STATE_CONNECTED);
}

/**
 * Stop all threads
 */
public synchronized void stop() {
    if (D) Log.d(TAG, "stop");

    if (mConnectThread != null) {
        mConnectThread.cancel();
        mConnectThread = null;
    }

    if (mConnectedThread != null) {
        mConnectedThread.cancel();
        mConnectedThread = null;
    }

    if (mSecureAcceptThread != null) {
        mSecureAcceptThread.cancel();
        mSecureAcceptThread = null;
    }

    if (mInsecureAcceptThread != null) {
        mInsecureAcceptThread.cancel();
        mInsecureAcceptThread = null;
    }
    setState(STATE_NONE);
}

/**
 * Write to the ConnectedThread in an unsynchronized manner
 * @param out The bytes to write
 * @see ConnectedThread#write(byte[])
 */
public void write(byte[] out) {
    // Create temporary object
    ConnectedThread r;
    // Synchronize a copy of the ConnectedThread
    synchronized (this) {
        if (mState != STATE_CONNECTED) return;
        r = mConnectedThread;
    }
    // Perform the write unsynchronized
    r.write(out);
}

/**
 * Indicate that the connection attempt failed and notify the UI Activity.
 */
private void connectionFailed() {
    // Send a failure message back to the Activity
    Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_TOAST);
    Bundle bundle = new Bundle();
    bundle.putString(BluetoothChat.TOAST, "Unable to connect device");
    msg.setData(bundle);
    mHandler.sendMessage(msg);

    // Start the service over to restart listening mode
    BluetoothChatService.this.start();
}

/**
 * Indicate that the connection was lost and notify the UI Activity.
 */
private void connectionLost() {
    // Send a failure message back to the Activity
    Message msg = mHandler.obtainMessage(BluetoothChat.MESSAGE_TOAST);
    Bundle bundle = new Bundle();
    bundle.putString(BluetoothChat.TOAST, "Device connection was lost");
    msg.setData(bundle);
    mHandler.sendMessage(msg);

    // Start the service over to restart listening mode
    BluetoothChatService.this.start();
}

Answer 1

Does the UUID used for the server code written for the "custom made hardware", match with the UUID used on the Android phone? It maybe that the Nexus One may be the only phone (among your phones) that uses Gingerbread (?) and that would mean a higher API level, than previous versions of Android. Go through the change logs of Gingerbread relating to Bluetooth. That would probably be the reason.

Answer 2

Well the code had some errors ... they were solved once i went over the Activity's complete lifecycle and implemented according to that. The class given is fine.