藍牙傳遞數據是移動端經常使用的通信方式,Android中藍牙模塊依然很常用。本文就詳細講解Android藍牙模塊的使用方法。
1、使用藍牙的響應權限
XML/HTML代碼
- <uses-permission android:name="android.permission.BLUETOOTH" />
- <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
2、配置本機藍牙模塊
在這裡首先要了解對藍牙操作一個核心類BluetoothAdapter。
Java代碼
- BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
- //直接打開系統的藍牙設置面板
- Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
- startActivityForResult(intent, 0x1);
- //直接打開藍牙
- adapter.enable();
- //關閉藍牙
- adapter.disable();
- //打開本機的藍牙發現功能(默認打開120秒,可以將時間最多延長至300秒)
- discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//設置持續時間(最多300秒)Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
3、搜索藍牙設備
使用BluetoothAdapter的startDiscovery()方法來搜索藍牙設備。
startDiscovery()方法是一個異步方法,調用後會立即返回。該方法會進行對其他藍牙設備的搜索,該過程會持續12秒。該方法調用後,搜索過程實際上是在一個System Service中進行的,所以可以調用cancelDiscovery()方法來停止搜索(該方法可以在未執行discovery請求時調用)。
請求Discovery後,系統開始搜索藍牙設備,在這個過程中,系統會發送以下三個廣播:
ACTION_DISCOVERY_START:開始搜索
ACTION_DISCOVERY_FINISHED:搜索結束
ACTION_FOUND:找到設備,這個Intent中包含兩個extra fields:EXTRA_DEVICE和EXTRA_CLASS,分別包含BluetooDevice和BluetoothClass。
我們可以自己注冊相應的BroadcastReceiver來接收響應的廣播,以便實現某些功能。
Java代碼
- // 創建一個接收ACTION_FOUND廣播的BroadcastReceiver
- private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
- public void onReceive(Context context, Intent intent) {
- String action = intent.getAction();
- // 發現設備
- if (BluetoothDevice.ACTION_FOUND.equals(action)) {
- // 從Intent中獲取設備對象
- BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
- // 將設備名稱和地址放入array adapter,以便在ListView中顯示
- mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
- }
- }
- };
- // 注冊BroadcastReceiver
- IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
- registerReceiver(mReceiver, filter); // 不要忘了之後解除綁定
4、藍牙Socket通信
如果打算建議兩個藍牙設備之間的連接,則必須實現服務器端與客戶端的機制。當兩個設備在同一個RFCOMM channel下分別擁有一個連接的BluetoothSocket,這兩個設備才可以說是建立了連接。
服務器設備與客戶端設備獲取BluetoothSocket的途徑是不同的。服務器設備是通過accepted一個incoming connection來獲取的,而客戶端設備則是通過打開一個到服務器的RFCOMM channel來獲取的。
服務器端的實現
通過調用BluetoothAdapter的listenUsingRfcommWithServiceRecord(String, UUID)方法來獲取BluetoothServerSocket(UUID用於客戶端與服務器端之間的配對)。
調用BluetoothServerSocket的accept()方法監聽連接請求,如果收到請求,則返回一個BluetoothSocket實例(此方法為block方法,應置於新線程中)。
如果不想在accept其他的連接,則調用BluetoothServerSocket的close()方法釋放資源(調用該方法後,之前獲得的BluetoothSocket實例並沒有close。但由於RFCOMM一個時刻只允許在一條channel中有一個連接,則一般在accept一個連接後,便close掉BluetoothServerSocket)。
Java代碼
- 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) { }
- }
- }
客戶端的實現
通過搜索得到服務器端的BluetoothService。
調用BluetoothService的listenUsingRfcommWithServiceRecord(String, UUID)方法獲取BluetoothSocket(該UUID應該同於服務器端的UUID)。
調用BluetoothSocket的connect()方法(該方法為block方法),如果UUID同服務器端的UUID匹配,並且連接被服務器端accept,則connect()方法返回。
注意:在調用connect()方法之前,應當確定當前沒有搜索設備,否則連接會變得非常慢並且容易失敗。
Java代碼
- 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(數據通信)
分別通過BluetoothSocket的getInputStream()和getOutputStream()方法獲取InputStream和OutputStream。
使用read(bytes[])和write(bytes[])方法分別進行讀寫操作。
注意:read(bytes[])方法會一直block,知道從流中讀取到信息,而write(bytes[])方法並不是經常的block(比如在另一設備沒有及時read或者中間緩沖區已滿的情況下,write方法會block)。
Java代碼
- 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) { }
- }
- }