How to read/receive data using bluetooth?

Question

I'm trying to make an app that can send and receive data via bluetooth from arduino. The part where i send the data is fairly simple so I've managed to get it right. I got stuck at receiving data.

My program has 2 layouts. First there is a layout with a CONNECT button and some buttons that change the layout. This is the code:

Public class MainActivity extends AppCompatActivity {
ImageButton test, manual,connect;
Button back;

private BluetoothAdapter mbluetoothAdapter;
protected AlertDialog.Builder builder;
ConnectThread mBluetooth = new ConnectThread();
String mBluetoothName = "";
String mBluetoothAdress = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final Context context = this;
    //final LayoutInflater factory = getLayoutInflater();
    //final View textEntryView = factory.inflate(R.layout.activity_main);
    builder = new AlertDialog.Builder(this);
    mbluetoothAdapter = BluetoothAdapter.getDefaultAdapter();


    connect = (ImageButton) findViewById(R.id.connect);
    test = (ImageButton) findViewById(R.id.test);
    manual = (ImageButton) findViewById(R.id.manual);


    test.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(context,SecondActivity.class );
            context.startActivity(intent);
        }

    });
    manual.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(context,SecondActivity.class );
            context.startActivity(intent);
        }

    });
    connect.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (!mbluetoothAdapter.isEnabled()) {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivity(enableBtIntent);
            } else {
                if (!mBluetooth.mBluetoothAddress.equals("")) {//if another connection is already exits then close it first
                    stopAllActivities();
                } else {
                    try {
                        Intent serverIntent = new Intent(MainActivity.this, DeviceListActivity.class);
                        startActivityForResult(serverIntent, Helper.REQUEST_CONNECT_DEVICE);
                    } catch (Exception e) {
                        showToast(getString(R.string.errorOccured) + ": " + e.getMessage());
                        e.printStackTrace();
                    }
                }
            }
        }
    });
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch (requestCode) {
        case Helper.REQUEST_CONNECT_DEVICE:
            if (resultCode == Activity.RESULT_OK) {
                mBluetoothName = data.getExtras().getString(Helper.EXTRA_BLUETOOTH_NAME);
                mBluetoothAdress = data.getExtras().getString(Helper.EXTRA_BLUETOOTH_ADDRESS);

                // setBluetoothInfo();
                showToast(R.string.connectedDevice + mBluetoothName);

                if (!mBluetoothAdress.equals("")) {
                    if (!mBluetooth.connect(mBluetoothAdress)){


                    }
                }
            }
            break;
    }
}

The SecondActivity contains the main purpose of this app: To send and receive data. This is how it looks like:

public class SecondActivity extends AppCompatActivity {
final Context context = this;
Button back;
ImageButton btnup, btndown, btnright, btnleft;
ConnectThread mBluetooth = new ConnectThread();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

btnup = (ImageButton) findViewById(R.id.btnup);
btndown = (ImageButton) findViewById(R.id.btndown);
btnleft = (ImageButton) findViewById(R.id.btnleft);
btnright = (ImageButton) findViewById(R.id.btnright);
final TextView direction = (TextView) findViewById(R.id.text_direction);
final TextView steering = (TextView) findViewById(R.id.steering_direction);
final TextView speed = (TextView) findViewById(R.id.speed);
final TextView battery = (TextView) findViewById(R.id.batery);
final Chronometer chronometer = (Chronometer) findViewById(R.id.chronometer);

btndown.setOnTouchListener(new View.OnTouchListener() {
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            mBluetooth.write("2");
            direction.setText(R.string.Backwards);
        } else if (event.getAction() == MotionEvent.ACTION_UP) {
            mBluetooth.write("x");
            direction.setText(R.string.blank);
        }


        return false;

    }
});

Note: I didnt post the whole code because i have more buttons with the exact same code as the one above.

For the Bluetooth connection i have 2 separate classes one called ConnectThread:

public class ConnectThread {
    BluetoothAdapter mBluetoothAdapter = null;
    BluetoothSocket mSocket = null;
    OutputStream mOutStream = null;
    InputStream mInStream=null;
    String mBluetoothAddress = "";

    public boolean connect(String bluetoothAddress) {
        if (!mBluetoothAddress.equals(bluetoothAddress) && !mBluetoothAddress.equals("")) {
            close();
        }

        mBluetoothAddress = bluetoothAddress;

        if (mBluetoothAdapter == null) {
            mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        }

        if (mBluetoothAdapter == null) {
            return false;
        }

        if (!mBluetoothAdapter.isEnabled()) {
            return false;
        }

        try {
            BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(mBluetoothAddress);

            if (mSocket == null) {
                mSocket = device.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));

                mSocket.connect();
            }
        } catch (IOException e) {
            mSocket = null;

            e.printStackTrace();
            return false;
        }

        try {
            mOutStream = mSocket.getOutputStream();
        } catch (IOException e) {
            mOutStream = null;

            e.printStackTrace();
            return false;
        }

        return true;
    }

    public boolean check() {
        if (mBluetoothAdapter == null) {
            mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        }

        if (mBluetoothAdapter == null) {
            return false;
        }

        if (!mBluetoothAdapter.isEnabled()) {
            return false;
        }
        if (!mSocket.isConnected()) {
            return false;
        }

        return true;
    }

    public boolean close() {
        try {
            if (mOutStream != null) {
                mOutStream.close();
            }

            if (mSocket != null) {
                mSocket.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }

        mOutStream = null;
        mSocket = null;

        return true;
    }

    public boolean write(String strData) {
        byte[] buffer = strData.getBytes();

        try {
            if (mOutStream != null && mBluetoothAdapter.getState() == BluetoothAdapter.STATE_ON) {
                mOutStream.write(buffer);
            }
            else {
                return false;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
}

And the other one DeviceListActivity:

public class DeviceListActivity extends Activity {
    private BluetoothAdapter mBtAdapter;
    private ArrayAdapter<String> mPairedDevicesArrayAdapter;
    private ArrayAdapter<String> mNewDevicesArrayAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Setup the window
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.device_list);

        // Set result CANCELED incase the user backs out
        setResult(Activity.RESULT_CANCELED);

        // Initialize the button to perform device discovery
        Button scanButton = (Button) findViewById(R.id.button_scan);
        scanButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                if (mBtAdapter == null)
                    return;

                doDiscovery();
                v.setVisibility(View.GONE);
            }
        });

        // Initialize array adapters. One for already paired devices and
        // one for newly discovered devices
        mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
        mNewDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);

        // Find and set up the ListView for paired devices
        ListView pairedListView = (ListView) findViewById(R.id.paired_devices);
        pairedListView.setAdapter(mPairedDevicesArrayAdapter);
        pairedListView.setOnItemClickListener(mDeviceClickListener);

        // Find and set up the ListView for newly discovered devices
        ListView newDevicesListView = (ListView) findViewById(R.id.new_devices);
        newDevicesListView.setAdapter(mNewDevicesArrayAdapter);
        newDevicesListView.setOnItemClickListener(mDeviceClickListener);

        // Register for broadcasts when a device is discovered
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        this.registerReceiver(mReceiver, filter);

        // Register for broadcasts when discovery has finished
        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.registerReceiver(mReceiver, filter);

        // Get the local Bluetooth adapter
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBtAdapter == null) {
            mPairedDevicesArrayAdapter.add("DUMMY\n00:00:00:00:00:00");
            return;
        }

        // Get a set of currently paired devices
        Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();

        // If there are paired devices, add each one to the ArrayAdapter
        if (pairedDevices.size() > 0) {
            findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
            for (BluetoothDevice device : pairedDevices) {
                mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            }
        } else {
            String noDevices = getResources().getText(R.string.none_paired).toString();
            mPairedDevicesArrayAdapter.add(noDevices);
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // Make sure we're not doing discovery anymore
        if (mBtAdapter != null)
            mBtAdapter.cancelDiscovery();

        // Unregister broadcast listeners
        this.unregisterReceiver(mReceiver);
    }

    /**
     * Start device discover with the BluetoothAdapter
     */
    private void doDiscovery() {
        if (mBtAdapter == null)
            return;

        // Indicate scanning in the title
        setProgressBarIndeterminateVisibility(true);
        setTitle(R.string.scanning);

        // Turn on sub-title for new devices
        findViewById(R.id.title_new_devices).setVisibility(View.VISIBLE);

        // If we're already discovering, stop it
        if (mBtAdapter.isDiscovering()) {
            mBtAdapter.cancelDiscovery();
        }

        // Request discover from BluetoothAdapter
        mBtAdapter.startDiscovery();
    }

    // The on-click listener for all devices in the ListViews
    private AdapterView.OnItemClickListener mDeviceClickListener = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
            if (mBtAdapter != null) {
                // Cancel discovery because it's costly and we're about to connect
                mBtAdapter.cancelDiscovery();
            }

            // Get the device MAC address, which is the last 17 chars in the View
            String info = ((TextView) v).getText().toString();
            String name = info.substring(0, info.length() - 18);
            String address = info.substring(info.length() - 17);

            // Create the result Intent and include the MAC address
            Intent intent = new Intent();
            intent.putExtra(Helper.EXTRA_BLUETOOTH_ADDRESS, address);
            intent.putExtra(Helper.EXTRA_BLUETOOTH_NAME, name);

            // Set result and finish this Activity
            setResult(Activity.RESULT_OK, intent);

            finish();
        }
    };

    // The BroadcastReceiver that listens for discovered devices and
    // changes the title when discovery is finished
    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            // When discovery finds a device
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                // Get the BluetoothDevice object from the Intent
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                // If it's already paired, skip it, because it's been listed already
                if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
                    for (int i = 0; i < mNewDevicesArrayAdapter.getCount(); i++) {
                        if (mNewDevicesArrayAdapter.getItem(i).equals(device.getName() + "\n" + device.getAddress())) {
                            return;
                        }
                    }
                    mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
                }
                // When discovery is finished, change the Activity title
            } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                setProgressBarIndeterminateVisibility(false);
                setTitle(R.string.select_device);
                if (mNewDevicesArrayAdapter.getCount() == 0) {
                    String noDevices = getResources().getText(R.string.none_found).toString();
                    mNewDevicesArrayAdapter.add(noDevices);
                }
            }
        }
    };
}

I want to update two TextView with the data i receive from arduino. The data would look something like #first_data,second_data* where # is the start of data series and * the end. I would appreciate if you can help me with some advice/code how to do that. I am pretty new to java and I still dont fully understand how everything works.

Answer 1

Once you get the Bluetooth socket you could use its stream to read/write the content.

... 
m_Input = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
m_Output = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
...
// reading from stream
 m_Input.read(buffer, readBytes, 1) ;

you could use m_Input.available() to check if is any data available into stream. Otherwise the read method will block until you will read the number of bytes you specified as third argument.

 int readBytes=0;
 while(readBytes < expectedBytes){
   timeout = 0;
   while((m_Input.available()) == 0 && timeout < ReadTimeout) {
     timeout+=250;
     // throws interrupted exception
     Thread.sleep(250);// let control to other threads
     }
     if(timeout >= ReadTimeout){
       // throw new timeout exception
     }
     if (m_Input.read(buffer, readBytes, 1) == -1) {
       // throw stream/socket closed 
     }
     readBytes++;
 }

Ad for writing use write method

...    
//writting to stream
     m_Output.write(buffer,..);