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第105章、蓝牙(从零开始学Android) - jianghuiquan的专栏

[日期:2013-03-25] 来源:  作者: [字体: ]

  蓝牙,是一种支持设备短距离通信(一般10m内,且无阻隔媒介)的无线电技术。能在包括移动电话、PDA、无线耳机、笔记本电脑、蓝牙打印机等众多设备之间进行无线信息交换。

  

1. 使用蓝牙的响应权限

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


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

 
?
01 BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
02 //直接打开系统的蓝牙设置面板
03 Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
04 startActivityForResult(intent, 0x1);
05 //直接打开蓝牙
06 adapter.enable();
07 //关闭蓝牙
08 adapter.disable();
09 //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)
10 discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//设置持续时间(最多300秒)Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);

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

 
 
01 // 创建一个接收ACTION_FOUND广播的BroadcastReceiver
02 private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
03 public void onReceive(Context context, Intent intent) {
04 String action = intent.getAction();
05 // 发现设备
06 if (BluetoothDevice.ACTION_FOUND.equals(action)) {
07 // 从Intent中获取设备对象
08 BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
09 // 将设备名称和地址放入array adapter,以便在ListView中显示
10 mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
11 }
12 }
13 };
14 // 注册BroadcastReceiver
15 IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
16 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

 
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

 
?
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>

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)

 
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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