Bluetooth Framework For Android

Α framework for easily connecting multiple Android devices via bluetooth and sending String messages (not chat messages, anything really). Right now it can support 10 devices.

• Enable the device's bluetooth.
• Make the device discoverable.
• Discover other devices.
• Connect with other devices.
• Send String messages.

#How it works

One device takes up the role of the host. The other devices connect to the host. Behind the scenes, every message is sent to the host who appropriately forwards it. A message can be be sent to all devices connected to the host (global message) or to a single device

#How to use

1. Add BluetoothManager fragment to your activity.

private BluetoothManager bluetoothManager; //field declaration
@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  if (savedInstanceState == null) {
  bluetoothManager = new BluetoothManager(); //create a new BluetoothManager object
    getFragmentManager().beginTransaction() //Add it to the activity
    .add(bluetoothManager, "Bluetooth Manager Tag")
    .commit();
  }
}

2)Use BluetoothManager to be discovered/discover other nearby devices.

//Discover other devices
bluetoothManager.ensureDiscoverable(); //The device is now discoverable by other devices

//Be discovered. First set the listener
bluetoothManager.setBluetoothGetAvailableDevicesListener(new BluetoothGetAvailableDevicesListener() {
  @Override
  public void onDeviceFound(BluetoothDevice device) { //A device was found.
    addDeviceInList(device); //In this case, when we find a device we want to add in a list with nearby devices.
  }
});
bluetoothManager.getAvailableDevices(); //Start searching for other devices. 

3a)Accept incoming connections (host).

bluetoothManager.setServerListenForConnectionsListener(new ServerListenForConnectionsListener() { //Set the listener
    @Override
    public void onConnectionEstablished(boolean established, String name) { //Connected with a device
        if (established) {
            Toast.makeText(context, "Connected with " + name, Toast.LENGTH_SHORT).show();
        }
    }
});
btManager.serverListenForConnections(true); //if true, when a device connects, it will start listening for incoming connections again

3b)Connect to the host.

btManager.setConnectListener(new ConnectListener() { //Set the listener
  @Override
  public void onConnected(boolean connected, String deviceName) { //Connected to the device (the host)
    if(connected){
      Toast.makeText(context, "Connected to " + deviceName, Toast.LENGTH_SHORT).show();
    }
  }
});
bluetoothManager.connect(host's MAC); //Connect to the specified MAC (the host)

4)Bind to the SocketManagerService to receive and send messages.

private SocketManagerService mService; //You can access the Service's method via this object.
private boolean mBound = false;        //True if the service is bound and you can use it.
//Don't forget to start the service
startService(new Intent(this, SocketManagerService.class));

// Defines callbacks for service binding, passed to bindService()
private final ServiceConnection mConnection = new ServiceConnection() {
  @Override
  public void onServiceConnected(ComponentName className, IBinder service) {
    SocketManagerServiceBinder binder = (SocketManagerServiceBinder) service;
    mService = binder.getService();
    mBound = true;
    mService.addHandler(mHandler); //Messages are received through the handler. More in a bit.
  }
  @Override
  public void onServiceDisconnected(ComponentName arg0) {
    mBound = false;
  }
};

// Bind to SocketManagerService onStart
@Override
public void onStart() {
    super.onStart();
    Intent intent = new Intent(context, SocketManagerService.class);
    context.bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
}

//Unbind onStop.
@Override
public void onStop() {
  super.onStop();
  if (mBound) {
    mService.removeHandler(mHandler);
    context.unbindService(mConnection);
    mBound = false;
  }
}

5)Send messages

//Global message, to every device, including the sending device.
 mService.sendGlobalMessage(message, appCode); //int appCode is user defined use it to distinguish your messages (chat, control etc).

//Private message, sent only to the specified device.
String targetMAC = mService.getMAC(targetName); //Gets the MAC from the list of connected devices.
if (targetMAC == null) { //If the device isn't the host, getMAC will return null
    mService.sendPrivateMessage(message, targetName, CHAT_PRIVATE); //The host will search for the correct device.
} else {
    mService.sendPrivateMessage(message, targetMAC, CHAT_PRIVATE); //targetMAC is known, send the message.
}

6)Receive messages

private MyHandler mHandler;
private static class ChatHandler extends Handler {
  final WeakReference<T> weakRef; //Use this if you want to refer to an object in your activity or fragment.
                                  //ie. if you were making a chat app, you could put your chat adapter.
  ChatHandler(T object) {
    weakRef = new WeakReference<>(object);
  }
  @Override
    public void handleMessage(Message msg) {
      if (msg.what != appCode) return; //Ignore the appCodes that aren't relevenant.
      String message = (String) msg.obj;
    }
  }