Thread: UI hangs while sending data on bluetooth.

Hello All,

This is my first post to this forum. I am new to android development. I am trying to write a client application which talk to server application via bluetooth. Server application is running on embedded platfrom.

I referred bluetoothchat example for bluetooth data transfer. In my application I have two activities, Main activity shows list of bluetooth devices and when a user clicks on one of the devices it will open a new activity. Then it will open a bluetooth socket start thread to connect to server. I have a message handler which talks to the connected thread.

my codes looks like this

1protected static final int SUCCESS_CONNECT = 0;
2	protected static final int MESSAGE_READ = 1;
3	protected static final int RECIEVE_MESSAGE = 2; // Status for Handler
4 public BluetoothSocket mmSocket;
5 public InputStream mmInStream;
6 public OutputStream mmOutStream;
7	String tag = "debugging";
8	
9	private BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
10	Handler mHandler = new Handler(){
11	@Override
12	public void handleMessage(Message msg)
13	{
14	// TODO Auto-generated method stub
15	Log.i(tag, "in handler");
16	super.handleMessage(msg);
17	switch(msg.what){
18	case SUCCESS_CONNECT:
19	// DO something
20	ConnectedThread connectedThread = new ConnectedThread((BluetoothSocket)msg.obj);
21	//Toast.makeText(getApplicationContext(), "CONNECT", 0).show();
22	String s = "successfully connected";
23	//connectedThread.write(s.getBytes());
24	connectedThread.write(s.getBytes());
25	Log.i(tag, "connected");
26	break;
27	case MESSAGE_READ:
28	byte[] readBuf = (byte[])msg.obj;
29	//String string = new String(readBuf, 0, msg.arg1);
30	Toast.makeText(getApplicationContext(), "Test", 0).show();
31	// Create the text view
32	//TextView textView = (TextView)findViewById(R.id.rcvedMsg);
33	//textView.setTextSize(40);
34	//textView.setText(string);
35	break;
36	case RECIEVE_MESSAGE:
37	byte[] readmsgBuf = (byte[])msg.obj;
38	String string = new String(readmsgBuf, 0, msg.arg1);
39	Toast.makeText(getApplicationContext(), "Test", 0).show();
40	// Create the text view
41	//TextView textView = (TextView)findViewById(R.id.rcvedMsg);
42	//textView.setTextSize(40);
43	//textView.setText(string);
44	break;
45	}
46	}

private class ConnectedThread extends Thread
2	{
3	public ConnectedThread(BluetoothSocket socket)
4	{
5	mmSocket = socket;
6	InputStream tmpIn = null;
7	OutputStream tmpOut = null;
8	
9	// Get the input and output streams, using temp objects because
10	// member streams are final
11	try {
12	tmpIn = socket.getInputStream();
13	tmpOut = socket.getOutputStream();
14	} catch (IOException e) { }
15	
16	mmInStream = tmpIn;
17	mmOutStream = tmpOut;
18	}
19	
20	public void run() {
21	byte[] buffer ; // buffer store for the stream
22	int bytes; // bytes returned from read()
23
24	// Keep listening to the InputStream until an exception occurs
25	while (true) {
26	try {
27	// Read from the InputStream
28	buffer = new byte[1024];
29	bytes = mmInStream.read(buffer);
30	Log.d("MR", "input stream :"+(new String(buffer)));
31	// Send the obtained bytes to the UI activity
32	mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer).sendToTarget();
33	} catch (IOException e) {
34	break;
35	}
36	}
37	}
38	
39	/* Call this from the main activity to send data to the remote device */
40	public void write(byte[] bytes) {
41	try {
42	//a delay of 20ms occurs after each flush...
43	mmOutStream.write(bytes);
44	mmOutStream.flush();
45	} catch (IOException e) { }
46	}
47	
48	/* Call this from the main activity to shutdown the connection */
49	public void cancel() {
50	try {
51	mmSocket.close();
52	} catch (IOException e) { }
53	}
54	}

method to write to data to bluetooth on pressing a button.

1public void ledOff(View v ) throws IOException
2	{
3	//Toast.makeText(getApplicationContext(),"LED OFF", 0).show();
4/* if (mmSocket != null)
5	try {
6	mmSocket.getOutputStream().write('f');
7	} catch (IOException e) {
8	// TODO Auto-generated catch block
9	e.printStackTrace();
10	}
11*/
12	if(mmOutStream != null)
13	{
14	mmOutStream.write('f');
15	}
16	}

Some times my UI hangs when I click a button, it takes ages to respond back. In my method for ledOn I call bluetooth input stream. Is this correct method to do it.

Can some one please share some views on this.
Thanks

Hi Aussiemcgr,

Thanks for your reply, I am new to android development so I started with bluetooth chat example which is based on threads.

I guess I should read more about threads and AsyncTask. I noticed one more thing the problem which I mentioned earlier happens randomly. If i restart the tablet then i dont see this problem. Could it be that if my application crashed earlier it didnt close the threads and bluetooth sockets.

Check the log for error messages

Thanks your comments Aussiemcgr. Sorry for delayed reply i was writting the application for the embedded device which interacts with the tablet via bluetooth. It seems that from the UI thread i am sending bluetooth data, bluetooth is running a different thread, hence its kind of messing thing. I am going to give AsyncTask a try.