如何让蓝牙 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，我们的目标是让我们的蓝牙 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电路板。

这是我当前的代码：

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);
    }
}

即使回退到反射，某些设备上的连接也会间歇性失败。我收到以下错误：

find_rfc_slot_by_id unable to find RFCOMM slot id: XX（XX 是一个在每次尝试连接时递增的数字）。

接着是： 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。我正在两个平板电脑上进行测试。一款平板电脑，三星 Galaxy Tab 4 似乎工作得非常好，而另一款平板电脑，Astro Tab A10，似乎有点断断续续，除非你在连接和断开之间等待几秒钟。

Answer 1

为了更可靠的连接意味着即使应用程序关闭，蓝牙也应在后台保持连接。 以下是我在我的应用程序中遵循的工作解决方案，以保持蓝牙连接背景。 首先创建一个扩展服务的类，因为服务在后台运行，即使应用程序关闭，直到您调用 stopService 或 stopSelf 方法

在启动 BluetoothService 类时，通过蓝牙 Mac 地址连接并在后台运行。 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