如何使蓝牙SPP连接过程更可靠？

Question

我们即将发布我们软件的新版本,对于之后的版本,我们的目标是使我们的蓝牙SPP连接的连接过程更加可靠.我们在产品中使用RN42模块,目前有时可能需要多次尝试才能连接到我们的主板.

这是我目前的代码:

class ConnectThread extends Thread {
    BluetoothDevice mDevice;

    public ConnectThread(BluetoothDevice device) throws SecurityException, NoSuchMethodException {
        mDevice = device;
        UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
        try {
            btSocket = mDevice.createInsecureRfcommSocketToServiceRecord(uuid);
        } catch (IOException e) {
            Log.e("Error", "Could not create socket!");
        }
    }

    public void cancel() {
        interrupt();
        try {
            Log.i("Treadmill", "in connect thread cancellation");
            btSocket.close();
        } catch (IOException localIOException) {
            Log.e("Treadmill", "exception + " + localIOException.getMessage());
        }
    }

    public void run() {
        btAdapter.cancelDiscovery();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            Log.e("whatever", "InterruptedException: " + e.getMessage(), e);
        }
        try {
            btSocket.connect();
            Log.i("Treadmill", "After Connect");
        } catch (IOException ioe) {
            Log.i("Treadmill", "Trying Fallback");
            try {
                Method m;
                try {
                    btSocket.close();
                    m = mDevice.getClass().getMethod("createInsecureRfcommSocket", new Class[]{int.class});
                    btSocket = (BluetoothSocket) m.invoke(mDevice, 1);
                    Thread.sleep(500);
                    btSocket.connect();
                } catch (IllegalArgumentException e) {
                    Log.e("whatever", "IllegalArgumentException: " + e.getMessage(), e);
                } catch (IllegalAccessException e) {
                    Log.e("whatever", "IllegalAccessException: " + e.getMessage(), e);
                } catch (InvocationTargetException e) {
                    Log.e("whatever", "InvocationTargetException: " + e.getMessage(), e);
                } catch (NoSuchMethodException e) {
                    Log.e("whatever", "NoSuchMethodException: " + e.getMessage(), e);
                } catch (InterruptedException e) {
                    Log.e("whatever", "InterruptedException: " + e.getMessage(), e);
                }

            } catch (IOException ioe2) {
                Log.e("Treadmill", "Failed to connect to Bluetooth device: " + ioe2.getMessage());
                eventHandler.obtainMessage(MESSAGE_ERRORCONNECT, 0, 0, getResources().getString(R.string.connerr) + ": " + ioe2.getMessage()).sendToTarget();
                try {
                    btSocket.close();
                } catch (IOException localIOException2) {
                    Log.e("Error", "IO Exception!");
                }
                return;
            }
        }
        eventHandler.obtainMessage(MESSAGE_CONNECT, 0, 0, "").sendToTarget();
        synchronized (this) {
            connectThread = null;
        }
        manageConnectedSocket(btSocket);
    }
}

即使有反映的后退,连接也会在某些设备上间歇性地失败.我收到以下错误:

find_rfc_slot_by_id unable to find RFCOMM slot id: XX(XX是每次尝试连接时递增的数字).

接下来是这样的: Failed to connect to Bluetooth device: read failed, socket might closed or timeout, read ret: -1

有谁知道如何避免这些错误.

有趣的是,为了比较.我正在测试两款平板电脑.一台平板电脑,三星Galaxy Tab 4似乎运行得非常好,而另一台,Astro Tab A10,似乎有点间断,除非你在连接和断开连接之间等待几秒钟.

Answer 1

为了更可靠的连接意味着即使应用程序关闭，蓝牙也应该在后台保持连接。以下是我在应用程序中遵循的用于保持蓝牙连接后台的工作解决方案。首先创建一个扩展服务的类，因为即使应用程序关闭，服务也会在后台运行，直到您调用 stopService 或 stopSelf 方法

当启动BluetoothService类时，会传递蓝牙Mac地址以进行连接并在后台运行。示例代码：

   @Override
public int onStartCommand(Intent intent, int flags, int startId) {

    if (intent != null){
        String deviceg = intent.getStringExtra("bluetooth_device");

        if (deviceg != null){
            connectToDevice(deviceg);
        }

    }

    return START_STICKY;
}

下面是连接到设备的方法，它将 MAC 地址识别到蓝牙设备中。

   public synchronized void connectToDevice(String macAddress){
    BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(macAddress);

    if (mConnectedThread != null){
        mConnectedThread.cancel();
        mConnectedThread = null;
    }
    mConnectThread = new ConnectBtThread(device);
    toast("connecting");
    mConnectThread.start();

}

这是我在 BluetoothService 中的 Thread 类，它在单独的线程中运行代码：

 private class ConnectBtThread extends Thread{
    private final BluetoothSocket mSocket;
    private final BluetoothDevice mDevice;

    public ConnectBtThread(BluetoothDevice device){
        mDevice = device;
        BluetoothSocket socket = null;
        try {
            socket = device.createInsecureRfcommSocketToServiceRecord(UUID.fromString(B_UUID));
        } catch (IOException e) {
            e.printStackTrace();
        }
        mSocket = socket;

    }

    @Override
    public void run() {
        if (mBluetoothAdapter.isDiscovering()){
            mBluetoothAdapter.cancelDiscovery();
        }

        try {
            mSocket.connect();
            Log.d("service","Bluetooth one running (connected)");

        } catch (IOException e) {

            try {
                mSocket.close();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            e.printStackTrace();
        }
        connected(mSocket);

    }

    public void cancel(){

        try {
            mSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

它非常适合我们的应用程序。如果您想访问服务方法，请将此服务绑定到您的活动