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Android藍(lán)牙開發(fā)深入解析

2020-04-11 12:02:01
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1. 使用藍(lán)牙的響應(yīng)權(quán)限

復(fù)制代碼 代碼如下:

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

2. 配置本機(jī)藍(lán)牙模塊

在這里首先要了解對(duì)藍(lán)牙操作一個(gè)核心類BluetoothAdapter

復(fù)制代碼 代碼如下:

BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
//直接打開系統(tǒng)的藍(lán)牙設(shè)置面板
Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent, 0x1);
//直接打開藍(lán)牙
adapter.enable();
//關(guān)閉藍(lán)牙
adapter.disable();
//打開本機(jī)的藍(lán)牙發(fā)現(xiàn)功能(默認(rèn)打開120秒,可以將時(shí)間最多延長至300秒)
Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//設(shè)置持續(xù)時(shí)間(最多300秒)

3.搜索藍(lán)牙設(shè)備

使用BluetoothAdapter的startDiscovery()方法來搜索藍(lán)牙設(shè)備

startDiscovery()方法是一個(gè)異步方法,調(diào)用后會(huì)立即返回。該方法會(huì)進(jìn)行對(duì)其他藍(lán)牙設(shè)備的搜索,該過程會(huì)持續(xù)12秒。該方法調(diào)用后,搜索過程實(shí)際上是在一個(gè)System Service中進(jìn)行的,所以可以調(diào)用cancelDiscovery()方法來停止搜索(該方法可以在未執(zhí)行discovery請(qǐng)求時(shí)調(diào)用)。

請(qǐng)求Discovery后,系統(tǒng)開始搜索藍(lán)牙設(shè)備,在這個(gè)過程中,系統(tǒng)會(huì)發(fā)送以下三個(gè)廣播:

ACTION_DISCOVERY_START:開始搜索

ACTION_DISCOVERY_FINISHED:搜索結(jié)束

ACTION_FOUND:找到設(shè)備,這個(gè)Intent中包含兩個(gè)extra fields:EXTRA_DEVICE和EXTRA_CLASS,分別包含BluetooDevice和BluetoothClass。

我們可以自己注冊(cè)相應(yīng)的BroadcastReceiver來接收響應(yīng)的廣播,以便實(shí)現(xiàn)某些功能

復(fù)制代碼 代碼如下:

// 創(chuàng)建一個(gè)接收ACTION_FOUND廣播的BroadcastReceiver
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        // 發(fā)現(xiàn)設(shè)備
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // 從Intent中獲取設(shè)備對(duì)象
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // 將設(shè)備名稱和地址放入array adapter,以便在ListView中顯示
            mArrayAdapter.add(device.getName() + "/n" + device.getAddress());
        }
    }
};
// 注冊(cè)BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // 不要忘了之后解除綁定

4. 藍(lán)牙Socket通信

如果打算建議兩個(gè)藍(lán)牙設(shè)備之間的連接,則必須實(shí)現(xiàn)服務(wù)器端與客戶端的機(jī)制。當(dāng)兩個(gè)設(shè)備在同一個(gè)RFCOMM channel下分別擁有一個(gè)連接的BluetoothSocket,這兩個(gè)設(shè)備才可以說是建立了連接。

服務(wù)器設(shè)備與客戶端設(shè)備獲取BluetoothSocket的途徑是不同的。服務(wù)器設(shè)備是通過accepted一個(gè)incoming connection來獲取的,而客戶端設(shè)備則是通過打開一個(gè)到服務(wù)器的RFCOMM channel來獲取的。

服務(wù)器端的實(shí)現(xiàn)

通過調(diào)用BluetoothAdapter的listenUsingRfcommWithServiceRecord(String, UUID)方法來獲取BluetoothServerSocket(UUID用于客戶端與服務(wù)器端之間的配對(duì))

調(diào)用BluetoothServerSocket的accept()方法監(jiān)聽連接請(qǐng)求,如果收到請(qǐng)求,則返回一個(gè)BluetoothSocket實(shí)例(此方法為block方法,應(yīng)置于新線程中)

如果不想在accept其他的連接,則調(diào)用BluetoothServerSocket的close()方法釋放資源(調(diào)用該方法后,之前獲得的BluetoothSocket實(shí)例并沒有close。但由于RFCOMM一個(gè)時(shí)刻只允許在一條channel中有一個(gè)連接,則一般在accept一個(gè)連接后,便close掉BluetoothServerSocket)

復(fù)制代碼 代碼如下:

private class AcceptThread extends Thread {
    private final BluetoothServerSocket mmServerSocket;

    public AcceptThread() {
        // Use a temporary object that is later assigned to mmServerSocket,
        // because mmServerSocket is final
        BluetoothServerSocket tmp = null;
        try {
            // MY_UUID is the app's UUID string, also used by the client code
            tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
        } catch (IOException e) { }
        mmServerSocket = tmp;
    }

    public void run() {
        BluetoothSocket socket = null;
        // Keep listening until exception occurs or a socket is returned
        while (true) {
            try {
                socket = mmServerSocket.accept();
            } catch (IOException e) {
                break;
            }
            // If a connection was accepted
            if (socket != null) {
                // Do work to manage the connection (in a separate thread)
                manageConnectedSocket(socket);
                mmServerSocket.close();
                break;
            }
        }
    }

    /** Will cancel the listening socket, and cause the thread to finish */
    public void cancel() {
        try {
            mmServerSocket.close();
        } catch (IOException e) { }
    }
}


客戶端的實(shí)現(xiàn)
通過搜索得到服務(wù)器端的BluetoothService

調(diào)用BluetoothService的listenUsingRfcommWithServiceRecord(String, UUID)方法獲取BluetoothSocket(該UUID應(yīng)該同于服務(wù)器端的UUID)

調(diào)用BluetoothSocket的connect()方法(該方法為block方法),如果UUID同服務(wù)器端的UUID匹配,并且連接被服務(wù)器端accept,則connect()方法返回

注意:在調(diào)用connect()方法之前,應(yīng)當(dāng)確定當(dāng)前沒有搜索設(shè)備,否則連接會(huì)變得非常慢并且容易失敗

復(fù)制代碼 代碼如下:

private class ConnectThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final BluetoothDevice mmDevice;

    public ConnectThread(BluetoothDevice device) {
        // Use a temporary object that is later assigned to mmSocket,
        // because mmSocket is final
        BluetoothSocket tmp = null;
        mmDevice = device;

        // Get a BluetoothSocket to connect with the given BluetoothDevice
        try {
            // MY_UUID is the app's UUID string, also used by the server code
            tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
        } catch (IOException e) { }
        mmSocket = tmp;
    }

    public void run() {
        // Cancel discovery because it will slow down the connection
        mBluetoothAdapter.cancelDiscovery();

        try {
            // Connect the device through the socket. This will block
            // until it succeeds or throws an exception
            mmSocket.connect();
        } catch (IOException connectException) {
            // Unable to connect; close the socket and get out
            try {
                mmSocket.close();
            } catch (IOException closeException) { }
            return;
        }

        // Do work to manage the connection (in a separate thread)
        manageConnectedSocket(mmSocket);
    }

    /** Will cancel an in-progress connection, and close the socket */
    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) { }
    }
}


連接管理(數(shù)據(jù)通信)
分別通過BluetoothSocket的getInputStream()和getOutputStream()方法獲取InputStream和OutputStream

使用read(bytes[])和write(bytes[])方法分別進(jìn)行讀寫操作

注意:read(bytes[])方法會(huì)一直block,知道從流中讀取到信息,而write(bytes[])方法并不是經(jīng)常的block(比如在另一設(shè)備沒有及時(shí)read或者中間緩沖區(qū)已滿的情況下,write方法會(huì)block)

復(fù)制代碼 代碼如下:

private class ConnectedThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final InputStream mmInStream;
    private final OutputStream mmOutStream;

    public ConnectedThread(BluetoothSocket socket) {
        mmSocket = socket;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the input and output streams, using temp objects because
        // member streams are final
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) { }

        mmInStream = tmpIn;
        mmOutStream = tmpOut;
    }

    public void run() {
        byte[] buffer = new byte[1024];  // buffer store for the stream
        int bytes; // bytes returned from read()

        // Keep listening to the InputStream until an exception occurs
        while (true) {
            try {
                // Read from the InputStream
                bytes = mmInStream.read(buffer);
                // Send the obtained bytes to the UI Activity
                mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
                        .sendToTarget();
            } catch (IOException e) {
                break;
            }
        }
    }

    /* Call this from the main Activity to send data to the remote device */
    public void write(byte[] bytes) {
        try {
            mmOutStream.write(bytes);
        } catch (IOException e) { }
    }

    /* Call this from the main Activity to shutdown the connection */
    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) { }
    }
}


引用資料:Android官方SDK、《Android/OPhone完全開發(fā)講義》

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