Android蓝牙开发浅析

由于近期正在开发一个通过蓝牙进行数据传递的模块，在参考了有关资料，并详细阅读了Android的官方文档后，总结了Android中蓝牙模块的使用。

1. 使用蓝牙的响应权限

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

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

2. 配置本机蓝牙模块

在这里首先要了解对蓝牙操作一个核心类BluetoothAdapter

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BluetoothAdapteradapter=BluetoothAdapter.getDefaultAdapter();
//直接打开系统的蓝牙设置面板
Intentintent=newIntent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent,0x1);
//直接打开蓝牙
adapter.enable();
//关闭蓝牙
adapter.disable();
//打开本机的蓝牙发现功能（默认打开120秒，可以将时间最多延长至300秒）
IntentdiscoveryIntent=newIntent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION,300);//设置持续时间（最多300秒）

BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); //直接打开系统的蓝牙设置面板 Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(intent, 0x1); //直接打开蓝牙 adapter.enable(); //关闭蓝牙 adapter.disable(); //打开本机的蓝牙发现功能（默认打开120秒，可以将时间最多延长至300秒） Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//设置持续时间（最多300秒）

3.搜索蓝牙设备

使用BluetoothAdapter的startDiscovery()方法来搜索蓝牙设备

startDiscovery()方法是一个异步方法，调用后会立即返回。该方法会进行对其他蓝牙设备的搜索，该过程会持续12秒。该方法调用后，搜索过程实际上是在一个System Service中进行的，所以可以调用cancelDiscovery()方法来停止搜索（该方法可以在未执行discovery请求时调用）。

请求Discovery后，系统开始搜索蓝牙设备，在这个过程中，系统会发送以下三个广播：

ACTION_DISCOVERY_START：开始搜索

ACTION_DISCOVERY_FINISHED：搜索结束

ACTION_FOUND：找到设备，这个Intent中包含两个extra fields：EXTRA_DEVICE和EXTRA_CLASS，分别包含BluetooDevice和BluetoothClass。

我们可以自己注册相应的BroadcastReceiver来接收响应的广播，以便实现某些功能

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//创建一个接收ACTION_FOUND广播的BroadcastReceiver
privatefinalBroadcastReceivermReceiver=newBroadcastReceiver(){
publicvoidonReceive(Contextcontext,Intentintent){
Stringaction=intent.getAction();
//发现设备
if(BluetoothDevice.ACTION_FOUND.equals(action)){
//从Intent中获取设备对象
BluetoothDevicedevice=intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
//将设备名称和地址放入arrayadapter，以便在ListView中显示
mArrayAdapter.add(device.getName()+"\n"+device.getAddress());
}
}
};
//注册BroadcastReceiver
IntentFilterfilter=newIntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver,filter);//不要忘了之后解除绑定

// 创建一个接收ACTION_FOUND广播的BroadcastReceiver private final BroadcastReceiver mReceiver = new BroadcastReceiver() { public void onReceive(Context context, Intent intent) { String action = intent.getAction(); // 发现设备 if (BluetoothDevice.ACTION_FOUND.equals(action)) { // 从Intent中获取设备对象 BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); // 将设备名称和地址放入array adapter，以便在ListView中显示 mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); } } }; // 注册BroadcastReceiver IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); registerReceiver(mReceiver, filter); // 不要忘了之后解除绑定

4. 蓝牙Socket通信

如果打算建议两个蓝牙设备之间的连接，则必须实现服务器端与客户端的机制。当两个设备在同一个RFCOMM channel下分别拥有一个连接的BluetoothSocket，这两个设备才可以说是建立了连接。

服务器设备与客户端设备获取BluetoothSocket的途径是不同的。服务器设备是通过accepted一个incoming connection来获取的，而客户端设备则是通过打开一个到服务器的RFCOMM channel来获取的。

服务器端的实现

通过调用BluetoothAdapter的listenUsingRfcommWithServiceRecord(String, UUID)方法来获取BluetoothServerSocket（UUID用于客户端与服务器端之间的配对）

调用BluetoothServerSocket的accept()方法监听连接请求，如果收到请求，则返回一个BluetoothSocket实例（此方法为block方法，应置于新线程中）

如果不想在accept其他的连接，则调用BluetoothServerSocket的close()方法释放资源（调用该方法后，之前获得的BluetoothSocket实例并没有close。但由于RFCOMM一个时刻只允许在一条channel中有一个连接，则一般在accept一个连接后，便close掉BluetoothServerSocket）

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privateclassAcceptThreadextendsThread{
privatefinalBluetoothServerSocketmmServerSocket;
publicAcceptThread(){
//UseatemporaryobjectthatislaterassignedtommServerSocket,
//becausemmServerSocketisfinal
BluetoothServerSockettmp=null;
try{
//MY_UUIDistheapp'sUUIDstring,alsousedbytheclientcode
tmp=mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME,MY_UUID);
}catch(IOExceptione){}
mmServerSocket=tmp;
}
publicvoidrun(){
BluetoothSocketsocket=null;
//Keeplisteninguntilexceptionoccursorasocketisreturned
while(true){
try{
socket=mmServerSocket.accept();
}catch(IOExceptione){
break;
}
//Ifaconnectionwasaccepted
if(socket!=null){
//Doworktomanagetheconnection(inaseparatethread)
manageConnectedSocket(socket);
mmServerSocket.close();
break;
}
}
}
/**Willcancelthelisteningsocket,andcausethethreadtofinish*/
publicvoidcancel(){
try{
mmServerSocket.close();
}catch(IOExceptione){}
}
}

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) { } } }

客户端的实现

通过搜索得到服务器端的BluetoothService

调用BluetoothService的listenUsingRfcommWithServiceRecord(String, UUID)方法获取BluetoothSocket（该UUID应该同于服务器端的UUID）

调用BluetoothSocket的connect()方法（该方法为block方法），如果UUID同服务器端的UUID匹配，并且连接被服务器端accept，则connect()方法返回

注意：在调用connect()方法之前，应当确定当前没有搜索设备，否则连接会变得非常慢并且容易失败

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privateclassConnectThreadextendsThread{
privatefinalBluetoothSocketmmSocket;
privatefinalBluetoothDevicemmDevice;
publicConnectThread(BluetoothDevicedevice){
//UseatemporaryobjectthatislaterassignedtommSocket,
//becausemmSocketisfinal
BluetoothSockettmp=null;
mmDevice=device;
//GetaBluetoothSockettoconnectwiththegivenBluetoothDevice
try{
//MY_UUIDistheapp'sUUIDstring,alsousedbytheservercode
tmp=device.createRfcommSocketToServiceRecord(MY_UUID);
}catch(IOExceptione){}
mmSocket=tmp;
}
publicvoidrun(){
//Canceldiscoverybecauseitwillslowdowntheconnection
mBluetoothAdapter.cancelDiscovery();
try{
//Connectthedevicethroughthesocket.Thiswillblock
//untilitsucceedsorthrowsanexception
mmSocket.connect();
}catch(IOExceptionconnectException){
//Unabletoconnect;closethesocketandgetout
try{
mmSocket.close();
}catch(IOExceptioncloseException){}
return;
}
//Doworktomanagetheconnection(inaseparatethread)
manageConnectedSocket(mmSocket);
}
/**Willcancelanin-progressconnection,andclosethesocket*/
publicvoidcancel(){
try{
mmSocket.close();
}catch(IOExceptione){}
}
}

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) { } } }

连接管理（数据通信）

分别通过BluetoothSocket的getInputStream()和getOutputStream()方法获取InputStream和OutputStream

使用read(bytes[])和write(bytes[])方法分别进行读写操作

注意：read(bytes[])方法会一直block，知道从流中读取到信息，而write(bytes[])方法并不是经常的block（比如在另一设备没有及时read或者中间缓冲区已满的情况下，write方法会block）

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privateclassConnectedThreadextendsThread{
privatefinalBluetoothSocketmmSocket;
privatefinalInputStreammmInStream;
privatefinalOutputStreammmOutStream;
publicConnectedThread(BluetoothSocketsocket){
mmSocket=socket;
InputStreamtmpIn=null;
OutputStreamtmpOut=null;
//Gettheinputandoutputstreams,usingtempobjectsbecause
//memberstreamsarefinal
try{
tmpIn=socket.getInputStream();
tmpOut=socket.getOutputStream();
}catch(IOExceptione){}
mmInStream=tmpIn;
mmOutStream=tmpOut;
}
publicvoidrun(){
byte[]buffer=newbyte[1024];//bufferstoreforthestream
intbytes;//bytesreturnedfromread()
//KeeplisteningtotheInputStreamuntilanexceptionoccurs
while(true){
try{
//ReadfromtheInputStream
bytes=mmInStream.read(buffer);
//SendtheobtainedbytestotheUIActivity
mHandler.obtainMessage(MESSAGE_READ,bytes,-1,buffer)
.sendToTarget();
}catch(IOExceptione){
break;
}
}
}
/*CallthisfromthemainActivitytosenddatatotheremotedevice*/
publicvoidwrite(byte[]bytes){
try{
mmOutStream.write(bytes);
}catch(IOExceptione){}
}
/*CallthisfromthemainActivitytoshutdowntheconnection*/
publicvoidcancel(){
try{
mmSocket.close();
}catch(IOExceptione){}
}
}

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) { } } }

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