Android 蓝牙连接到 ELM327/OBD2 设备

Question

我尝试创建一个简单的 android 应用程序来连接到我的 ELM327 设备以获取一些汽车诊断数据。但是我无法通过我的安卓手机和我的 ELM327 设备设置蓝牙连接。

我的代码很简单如下:

公共(public)类蓝牙{ protected 蓝牙适配器 mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); 私有(private)连接线程 mConnectThread = null； 私有(private) AcceptThread mAcceptThread = null； 私有(private) WorkerThread mWorkerThread = null； 私有(private)蓝牙设备 mOBDDevice = null； 私有(private)蓝牙套接字 mSocket = null； 私有(private)字符串 uuid;

Bluetooth() {
    mBluetoothAdapter= BluetoothAdapter.getDefaultAdapter();
    Set<BluetoothDevice> pairedDevices;


    if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled())
        return;

    pairedDevices = mBluetoothAdapter.getBondedDevices();
    if (pairedDevices.size() > 0) {
        // There are paired devices. Get the name and address of each paired device.
        for (BluetoothDevice device : pairedDevices) {
            String deviceName = device.getName();
            String deviceHardwareAddress = device.getAddress(); // MAC address
            //TODO: check whether this is OBD and whether it is connected
            //by sending a command and check response
            if (deviceName.contains("OBD")) {
                mOBDDevice = device;
                uuid = device.getUuids()[0].toString();
                break;
            }
        }
    }
    mBluetoothAdapter.cancelDiscovery();
}

/**
 * Start the chat service. Specifically start AcceptThread to begin a session
 * in listening (server) mode. Called by the Activity onResume()
 */
public synchronized void connect()
{
    try {
        // Get a BluetoothSocket to connect with the given BluetoothDevice.
        // MY_UUID is the app's UUID string, also used in the server code.
        mSocket = mOBDDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid));
    } catch (IOException e) {
        Log.e(TAG, "Socket's create() method failed", e);
    }

    try {
        // Connect to the remote device through the socket. This call blocks
        // until it succeeds or throws an exception.
        mSocket.connect();
    } catch (IOException connectException) {
        // Unable to connect; close the socket and return.
        try {
            mSocket.close();
        } catch (IOException closeException) {
            Log.e(TAG, "Could not close the client socket", closeException);
        }
        return;
    }
}

在主 Activity 中，我将首先新建一个蓝牙类，然后调用 bluetooth.connect():

mBluetooth = 新蓝牙(); mBluetooth.connect();

当我调试程序时，我能够通过查询所有名称为“OBD”的绑定(bind)设备来获取我的 ELM327 蓝牙设备。我还能够获取设备的 uuid 并使用 createRfcommSocketToServiceRecord 创建套接字。但是在connect函数中，mSocket.connect()总是失败，返回值为-1并得到IOexception。

我的问题是:

1. 当我的 android 应用程序连接到 ELM327 设备时，我的 android 手机是蓝牙客户端，而我的 ELM327 设备是蓝牙服务器，这种理解是否正确？
2. 是否有服务器程序在我的 ELM327 设备上运行以监听并接受传入连接？这是 ELM327 协议(protocol)的定义行为吗？
3. 知道为什么 mSocket.connect() 失败了吗？关于如何研究这个问题的任何想法？或者我的程序中有什么明显的错误？谢谢。

Answer 1

问题解决了。请参阅下面的源代码:

public synchronized void connect() throws IOException {
        try {
            // Get a BluetoothSocket to connect with the given BluetoothDevice.
            // MY_UUID is the app's UUID string, also used in the server code.
            mSocket = mOBDDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid));
        } catch (IOException e) {
            Log.e(TAG, "Socket's create() method failed", e);
        }

        try {
            // Connect to the remote device through the socket. This call blocks
            // until it succeeds or throws an exception.
            mSocket.connect();
        } catch (IOException e1) {
            Log.e(TAG, "There was an error while establishing Bluetooth connection. Falling back..", e1);
            Class<?> clazz = mSocket.getRemoteDevice().getClass();
            Class<?>[] paramTypes = new Class<?>[]{Integer.TYPE};
            try {
                Method m = clazz.getMethod("createRfcommSocket", paramTypes);
                Object[] params = new Object[]{Integer.valueOf(1)};
                mFallbackSocket = (BluetoothSocket) m.invoke(mSocket.getRemoteDevice(), params);
                mFallbackSocket.connect();
                mSocket.close();
                mSocket = mFallbackSocket;
            } catch (Exception e2) {
                Log.e(TAG, "Couldn't fallback while establishing Bluetooth connection.", e2);
                mSocket.close();
                //throw new IOException();
            }
        }
        inputStream = mSocket.getInputStream();
        outputStream = mSocket.getOutputStream();
    }