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 Android教程網 >> Android技術 >> Android技術基礎 >> 第105章、藍牙(從零開始學Android)

第105章、藍牙(從零開始學Android)

編輯:Android技術基礎

藍牙,是一種支持設備短距離通信(一般10m內,且無阻隔媒介)的無線電技術。能在包括移動電話、PDA、無線耳機、筆記本電腦、藍牙打印機等眾多設備之間進行無線信息交換。

 

1. 使用藍牙的響應權限

  1 <STRONG> <uses-permission android:name="android.permission.BLUETOOTH" /> 2 <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /> </STRONG>

 

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

    ? 01 BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); 02 //直接打開系統的藍牙設置面板 03 Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 04 startActivityForResult(intent, 0x1); 05 //直接打開藍牙 06 adapter.enable(); 07 //關閉藍牙 08 adapter.disable(); 09 //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) 10 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

    01 // 創建一個接收ACTION_FOUND廣播的BroadcastReceiver 02 private final BroadcastReceiver mReceiver = new BroadcastReceiver() { 03 public void onReceive(Context context, Intent intent) { 04 String action = intent.getAction(); 05 // 發現設備 06 if (BluetoothDevice.ACTION_FOUND.equals(action)) { 07 // 從Intent中獲取設備對象 08 BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 09 // 將設備名稱和地址放入array adapter,以便在ListView中顯示 10 mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); 11 } 12 } 13 }; 14 // 注冊BroadcastReceiver 15 IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 16 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)

    01 private class AcceptThread extends Thread { 02 private final BluetoothServerSocket mmServerSocket; 03   04 public AcceptThread() { 05 // Use a temporary object that is later assigned to mmServerSocket, 06 // because mmServerSocket is final 07 BluetoothServerSocket tmp = null; 08 try { 09 // MY_UUID is the app's UUID string, also used by the client code 10 tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID); 11 } catch (IOException e) { } 12 mmServerSocket = tmp; 13 } 14   15 public void run() { 16 BluetoothSocket socket = null; 17 // Keep listening until exception occurs or a socket is returned 18 while (true) { 19 try { 20 socket = mmServerSocket.accept(); 21 } catch (IOException e) { 22 break; 23 } 24 // If a connection was accepted 25 if (socket != null) { 26 // Do work to manage the connection (in a separate thread) 27 manageConnectedSocket(socket); 28 mmServerSocket.close(); 29 break; 30 } 31 } 32 } 33   34 /** Will cancel the listening socket, and cause the thread to finish */ 35 public void cancel() { 36 try { 37 mmServerSocket.close(); 38 } catch (IOException e) { } 39 } 40 }

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

    ? 01 <STRONG> private class ConnectThread extends Thread { 02 private final BluetoothSocket mmSocket; 03 private final BluetoothDevice mmDevice; 04   05 public ConnectThread(BluetoothDevice device) { 06 // Use a temporary object that is later assigned to mmSocket, 07 // because mmSocket is final 08 BluetoothSocket tmp = null; 09 mmDevice = device; 10   11 // Get a BluetoothSocket to connect with the given BluetoothDevice 12 try { 13 // MY_UUID is the app's UUID string, also used by the server code 14 tmp = device.createRfcommSocketToServiceRecord(MY_UUID); 15 } catch (IOException e) { } 16 mmSocket = tmp; 17 } 18   19 public void run() { 20 // Cancel discovery because it will slow down the connection 21 mBluetoothAdapter.cancelDiscovery(); 22   23 try { 24 // Connect the device through the socket. This will block 25 // until it succeeds or throws an exception 26 mmSocket.connect(); 27 } catch (IOException connectException) { 28 // Unable to connect; close the socket and get out 29 try { 30 mmSocket.close(); 31 } catch (IOException closeException) { } 32 return; 33 } 34   35 // Do work to manage the connection (in a separate thread) 36 manageConnectedSocket(mmSocket); 37 } 38   39 /** Will cancel an in-progress connection, and close the socket */ 40 public void cancel() { 41 try { 42 mmSocket.close(); 43 } catch (IOException e) { } 44 } 45 } </STRONG>

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)

    01 <STRONG> private class ConnectedThread extends Thread { 02 private final BluetoothSocket mmSocket; 03 private final InputStream mmInStream; 04 private final OutputStream mmOutStream; 05   06 public ConnectedThread(BluetoothSocket socket) { 07 mmSocket = socket; 08 InputStream tmpIn = null; 09 OutputStream tmpOut = null; 10   11 // Get the input and output streams, using temp objects because 12 // member streams are final 13 try { 14 tmpIn = socket.getInputStream(); 15 tmpOut = socket.getOutputStream(); 16 } catch (IOException e) { } 17   18 mmInStream = tmpIn; 19 mmOutStream = tmpOut; 20 } 21   22 public void run() { 23 byte[] buffer = new byte[1024]; // buffer store for the stream 24 int bytes; // bytes returned from read() 25   26 // Keep listening to the InputStream until an exception occurs 27 while (true) { 28 try { 29 // Read from the InputStream 30 bytes = mmInStream.read(buffer); 31 // Send the obtained bytes to the UI Activity 32 mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer) 33 .sendToTarget(); 34 } catch (IOException e) { 35 break; 36 } 37 } 38 } 39   40 /* Call this from the main Activity to send data to the remote device */ 41 public void write(byte[] bytes) { 42 try { 43 mmOutStream.write(bytes); 44 } catch (IOException e) { } 45 } 46   47 /* Call this from the main Activity to shutdown the connection */ 48 public void cancel() { 49 try { 50 mmSocket.close(); 51 } catch (IOException e) { } 52 } 53 } </STRONG>

 

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