Android笔记系列--(1)传统蓝牙 socket通讯方式

蓝牙是一种支持设备短距离传输数据的无线技术。android在2.0以后提供了这方面的支持。 
从查找蓝牙设备到能够相互通信要经过几个基本步骤(本机做为服务器)：


1. 设置权限 
在manifest中配置
<uses-permission android:name="android.permission.BLUETOOTH"/> 使用蓝牙所需要的权限
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/> 
使用扫描和设置蓝牙的权限（申明这一个权限必须申明上面一个权限）

在Android5.0之前，是默认申请GPS硬件功能的。而在Android 5.0 之后，需要在manifest 中申明GPS硬件模块功能的使用。

<!-- Needed only if your app targets Android 5.0 (API level 21) or higher. -->
<uses-feature android:name="android.hardware.location.gps" />
在 Android 6.0 及以上，还需要打开位置权限。如果应用没有位置权限，蓝牙扫描功能不能使用（其它蓝牙操作例如连接蓝牙设备和写入数据不受影响）。
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

2. 启动蓝牙 
首先要查看本机是否支持蓝牙，获取BluetoothAdapter蓝牙适配器对象

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); 
​
//或
//final BluetoothManager bluetoothManager = (BluetoothManager) //getSystemService(Context.BLUETOOTH_SERVICE); 
//mBluetoothAdapter = bluetoothManager.getAdapter();
​
if(mBluetoothAdapter == null){ 
        //表明此手机不支持蓝牙 
        return; 
} 
if(!mBluetoothAdapter.isEnabled()){ //蓝牙未开启，则开启蓝牙 
            Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT); 
} 
//…… 
public void onActivityResult(int requestCode, int resultCode, Intent data){ 
       if(requestCode == REQUEST_ENABLE_BT){ 
              if(requestCode == RESULT_OK){ 
                   //蓝牙已经开启  
              } 
       } 
} 

3. 发现蓝牙设备 
这里可以细分为几个方面 
(1) 使本机蓝牙处于可见(即处于易被搜索到状态)，便于其他设备发现本机蓝牙 

//使本机蓝牙在300秒内可被搜索
private void ensureDiscoverable() { 
        if (mBluetoothAdapter.getScanMode() != 
            BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) { 
            Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); 
            discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300); 
            startActivity(discoverableIntent); 
        } 
} 

(2)查找已经配对的蓝牙设备，即以前已经配对过的设备

Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); 
if (pairedDevices.size() > 0) { 
    findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE); 
    for (BluetoothDevice device : pairedDevices) { 
        //device.getName() +" "+ device.getAddress()); 
    } 
} else { 
    mPairedDevicesArrayAdapter.add("没有找到已匹对的设备"); 
} 

(3)通过mBluetoothAdapter.startDiscovery();搜索设备，要获得此搜索的结果需要注册一个BroadcastReceiver来获取。先注册再获取信息，然后处理

//注册，当一个设备被发现时调用onReceive 
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 
        this.registerReceiver(mReceiver, filter); 
​
//当搜索结束后调用onReceive 
filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED); 
        this.registerReceiver(mReceiver, filter); 
//……. 
private BroadcastReceiver mReceiver = new BroadcastReceiver() { 
        @Override 
        public void onReceive(Context context, Intent intent) { 
            String action = intent.getAction(); 
            if(BluetoothDevice.ACTION_FOUND.equals(action)){ 
                 BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
                  // 已经配对的则跳过 
                 if (device.getBondState() != BluetoothDevice.BOND_BONDED) { 
                      mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());  //保存设备地址与名字 
                 } 
            }else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {  //搜索结束 
                if (mNewDevicesArrayAdapter.getCount() == 0) { 
                    mNewDevicesArrayAdapter.add("没有搜索到设备"); 
                } 
            } 
​
        } 
}; 

4. 建立连接 
查找到设备后，则需要建立本机与其他设备之间的连接。 
一般用本机搜索其他蓝牙设备时，本机可以作为一个服务端，接收其他设备的连接。 
启动一个服务器端的线程，死循环等待客户端的连接，这与ServerSocket极为相似。 
这个线程在准备连接之前启动

//UUID可以看做一个端口号 
private static final UUID MY_UUID = 
        UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); 
   //像一个服务器一样时刻监听是否有连接建立 
    private class AcceptThread extends Thread{ 
        private BluetoothServerSocket serverSocket; 
​
        public AcceptThread(boolean secure){ 
            BluetoothServerSocket temp = null; 
            try { 
                temp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord( 
                            NAME_INSECURE, MY_UUID); 
            } catch (IOException e) { 
                  Log.e("app", "listen() failed", e); 
            } 
            serverSocket = temp; 
        } 
​
        public void run(){ 
            BluetoothSocket socket=null; 
            while(true){ 
                try { 
                    socket = serverSocket.accept(); 
                } catch (IOException e) { 
                     Log.e("app", "accept() failed", e); 
                     break; 
                } 
            } 
            if(socket!=null){ 
                //此时可以新建一个数据交换线程，把此socket传进去 
            } 
        } 
​
        //取消监听 
        public void cancel(){    
            try { 
                serverSocket.close(); 
            } catch (IOException e) { 
                Log.e("app", "Socket Type" + socketType + "close() of server failed", e); 
            } 
        } 
​
} 

搜索到设备后可以获取设备的地址，通过此地址获取一个BluetoothDeviced对象，可以看做客户端，通过此对象 device.createRfcommSocketToServiceRecord(MY_UUID);同一个UUID可与服务器建立连接获取另一个 socket对象，由此服务端与客户端各有一个socket对象，此时他们可以互相交换数据了。

创立客户端socket可建立线程

 //另一个设备去连接本机,相当于客户端 
 private class ConnectThread extends Thread{ 
    private BluetoothSocket socket; 
    private BluetoothDevice device; 
    public ConnectThread(BluetoothDevice device,boolean secure){ 
        this.device = device; 
        BluetoothSocket tmp = null; 
        try { 
    tmp = device.createRfcommSocketToServiceRecord(MY_UUID_SECURE); 
} catch (IOException e) { 
     Log.e("app", "create() failed", e); 
} 
    } 
​
    public void run(){ 
        mBluetoothAdapter.cancelDiscovery();    //取消设备查找 
        try { 
    socket.connect(); 
} catch (IOException e) { 
    try { 
        socket.close(); 
    } catch (IOException e1) { 
         Log.e("app", "unable to close() "+ 
                          " socket during connection failure", e1); 
    } 
    connetionFailed();  //连接失败 
    return; 
} 
      //此时可以新建一个数据交换线程，把此socket传进去 
    } 
​
      public void cancel() { 
           try { 
               socket.close(); 
           } catch (IOException e) { 
               Log.e("app", "close() of connect  socket failed", e); 
           } 
       } 
 } 

5. 建立数据通信线程，进行读取数据

//建立连接后，进行数据通信的线程 
    private class ConnectedThread extends Thread{ 
        private BluetoothSocket socket; 
        private InputStream inStream; 
        private OutputStream outStream; 
​
        public ConnectedThread(BluetoothSocket socket){ 
​
            this.socket = socket; 
            try { 
                //获得输入输出流 
                inStream = socket.getInputStream(); 
                outStream = socket.getOutputStream(); 
            } catch (IOException e) { 
                Log.e("app", "temp sockets not created", e); 
            } 
        } 
​
        public void run(){ 
            byte[] buff = new byte[1024]; 
            int len=0; 
            //读数据需不断监听，写不需要 
            while(true){ 
                try { 
                    len = inStream.read(buff); 
                    //把读取到的数据发送给UI进行显示 
                    Message msg = handler.obtainMessage(BluetoothChat.MESSAGE_READ, 
                            len, -1, buff); 
                    msg.sendToTarget(); 
                } catch (IOException e) { 
                    Log.e("app", "disconnected", e); 
                    connectionLost();   //失去连接 
                    start();    //重新启动服务器 
                    break; 
                } 
            } 
        } 
​
​
        public void write(byte[] buffer) { 
            try { 
                outStream.write(buffer); 
​
                // Share the sent message back to the UI Activity 
                handler.obtainMessage(BluetoothChat.MESSAGE_WRITE, -1, -1, buffer) 
                        .sendToTarget(); 
            } catch (IOException e) { 
                Log.e("app", "Exception during write", e); 
            } 
        } 
​
        public void cancel() { 
            try { 
                socket.close(); 
            } catch (IOException e) { 
                Log.e("app", "close() of connect socket failed", e); 
            } 
        } 
    } 

到这里，蓝牙通信的基本操作已经全部完成。

网上有个开源代码，包含了传统蓝牙和Ble外围模式的使用例子：

https://github.com/vir56k/bluetoothDemo