无法连接到蓝牙设备

Question

This is the piece of code from Standard from Google sample code BluetoothChat. BluetoothChatService.java

public void run() {
        Log.i(TAG, "BEGIN mConnectedThread");
        byte[] buffer = new byte[1024];
        int bytes;

        // Keep listening to the InputStream while connected
        while (mState == STATE_CONNECTED) {
            try {
                // Read from the InputStream
                bytes = mmInStream.read(buffer);
                // Send the obtained bytes to the UI Activity
                mHandler.obtainMessage(Constants.MESSAGE_READ, bytes, -1, buffer)
                        .sendToTarget();
            } catch (IOException e) {
                Log.e(TAG, "disconnected", e);
                connectionLost();
                break;
            }
        }
    }

As soon as I try to connect the device using

mChatService.connect(device, false);

I get following exception

java.io.IOException: bt socket closed, read return: -1
at android.bluetooth.BluetoothSocket.read(BluetoothSocket.java:872)
at android.bluetooth.BluetoothInputStream.read(BluetoothInputStream.java:96)
at java.io.InputStream.read(InputStream.java:163)

Any help would be appreciated.

Answer 1

Did you include in android manifest Bluetooth permission for your app?

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

Answer 2

I guess the problem is the mmSocket.connect()

Try to get the method createRfcommSocket by reflect.

Here is an example base on Google sample code BluetoothChat.

            // Make a connection to the BluetoothSocket
            try {
                Thread.sleep(500);
                // This is a blocking call and will only return on a
                // successful connection or an exception
                mmSocket.connect();
                OutputStream os = mmSocket.getOutputStream();
                // Here: connect success
            } catch (Exception e) {
                Log.i(TAG, "Lost 1st try; SPP connect[2]");
                try {
                    mmSocket.close();// close the current socket
                    mmSocket = null;
                    Thread.sleep(500L); // wait for a while
                    mmSocket = (BluetoothSocket) mmDevice.getClass().getMethod("createRfcommSocket", new Class[]{int.class}).invoke(mmDevice, 1); // The key method !
                    mmSocket.connect();
                    OutputStream os = mmSocket.getOutputStream();
                    // Here: connect success
                    synchronized (ESDevice.this) {
                        mSPPConnectThread = null;
                    }
                    connected(mmSocket, mmDevice); // begin connected thread
                } catch (Exception e2) {
                    Log.e(TAG, "Lost 2nd try. Connect fail", e2);
                    connectionFailed();
                    return;
                }
                return;
            }

Answer 3

It looks like socket was closed before you passed it in your mConnectedThread 's constructor.

There is one tricky thing in Google sample, in mConnectThread when socket was actually connected we make mConnectThread null, and next code won't be executed:

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

that means that cancel() method which closes the socket will be skipped.

Basically, make sure you don't call close() method in ConnectThread after your socket was connected.