Android 藍牙開發淺析

1. 使用藍牙的響應權限

 

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

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

2. 配置本機藍牙模塊

在這裡首先要瞭解對藍牙操作一個核心類BluetoothAdapter

[java]
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);   

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。

我們可以自己註冊相應的BroadcastReceiver來接收響應的廣播,以便實現某些功能

[java]
// 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());   
        }   
    }   
};   
// 註冊BroadcastReceiver    
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);   
registerReceiver(mReceiver, filter); // 不要忘瞭之後解除綁定   

// 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()); 
        } 
    } 
}; 
// 註冊BroadcastReceiver 
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 
registerReceiver(mReceiver, filter); // 不要忘瞭之後解除綁定 

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瞭連接。

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一個時刻隻允許在一條channel中有一個連接,則一般在accept一個連接後,便close掉BluetoothServerSocket)

[java]
<SPAN style="BACKGROUND-COLOR: rgb(255,255,255)"><STRONG>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) { } 
    } 
}</STRONG></SPAN> 

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createRfcommSocketToServiceRecord(MY_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

註意: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]
SPAN style="BACKGROUND-COLOR: rgb(255,255,255)"><STRONG><strong>    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) { }   
        }   
    }  </strong></STRONG></SPAN> 

<strong>    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) { } 
        } 
    }  </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

註意: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]
<SPAN style="BACKGROUND-COLOR: rgb(255,255,255)"><STRONG><strong>    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) { }   
        }   
    }  </strong></STRONG></SPAN> 

<strong>    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) { } 
        } 
    }  </strong>

 

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