Android 蓝牙

 

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正文

 

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

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();
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() + "
" + 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);
            }
        }
    }