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

startActivityForResult(new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE), 1);

<!-- 已适配Android6.0 -->
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> 
<uses-feature
  android:name="android.hardware.bluetooth_le"
  android:required="true" />

private static final int REQUEST_BLUETOOTH_PERMISSION=10;

private void requestBluetoothPermission(){
  //判断系统版本
  if (Build.VERSION.SDK_INT >= 23) {
    //检测当前app是否拥有某个权限
    int checkCallPhonePermission = ContextCompat.checkSelfPermission(this, 
        Manifest.permission.ACCESS_COARSE_LOCATION);
    //判断这个权限是否已经授权过
    if(checkCallPhonePermission != PackageManager.PERMISSION_GRANTED){
      //判断是否需要 向用户解释，为什么要申请该权限
      if(ActivityCompat.shouldShowRequestPermissionRationale(this, 
          Manifest.permission.ACCESS_COARSE_LOCATION))
        Toast.makeText(this,"Need bluetooth permission.", 
            Toast.LENGTH_SHORT).show();
      ActivityCompat.requestPermissions(this ,new String[]
          {Manifest.permission.ACCESS_COARSE_LOCATION},REQUEST_BLUETOOTH_PERMISSION);
      return;
    }else{
    }
  } else {
  }
}

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
mBluetoothAdapter.enable(); //开启
//mBluetoothAdapter.disable(); //关闭

TextView tvDevices = (TextView)findViewById(R.id.tv_devices);
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

//获取已经配对的蓝牙设备
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
  for (BluetoothDevice device : pairedDevices) {
    tvDevices.append(device.getName() + ":" + device.getAddress());
  }
}

// 设置广播信息过滤
IntentFilter filter = new IntentFilter();
filter.addAction(BluetoothDevice.ACTION_FOUND);//每搜索到一个设备就会发送一个该广播
filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);//当全部搜索完后发送该广播
filter.setPriority(Integer.MAX_VALUE);//设置优先级
// 注册蓝牙搜索广播接收者，接收并处理搜索结果
this.registerReceiver(receiver, filter);

/**
 * 定义广播接收器
 */
private final BroadcastReceiver receiver = 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);
      if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
        tvDevices.append(device.getName() + ":"+ device.getAddress());
      }
    } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
      //已搜素完成
    }
  }
};

//如果当前在搜索，就先取消搜索
if (mBluetoothAdapter.isDiscovering()) {
  mBluetoothAdapter.cancelDiscovery();
}
//开启搜索
mBluetoothAdapter.startDiscovery();

private ListView lvDevices;
private BluetoothAdapter mBluetoothAdapter;
private List<String> bluetoothDevices = new ArrayList<String>();
private ArrayAdapter<String> arrayAdapter;
private final UUID MY_UUID = UUID
    .fromString("abcd1234-ab12-ab12-ab12-abcdef123456");//随便定义一个
private BluetoothSocket clientSocket;
private BluetoothDevice device; 
private OutputStream os;//输出流

mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

lvDevices = (ListView) findViewById(R.id.lv_devices);
//获取已经配对的蓝牙设备
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
  for (BluetoothDevice device : pairedDevices) {
    bluetoothDevices.add(device.getName() + ":"+ device.getAddress());
  }
}
arrayAdapter = new ArrayAdapter<String>(this,
    android.R.layout.simple_list_item_1, android.R.id.text1,bluetoothDevices);
lvDevices.setAdapter(arrayAdapter);
lvDevices.setOnItemClickListener(this);//Activity实现OnItemClickListener接口

//每搜索到一个设备就会发送一个该广播
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
this.registerReceiver(receiver, filter);
//当全部搜索完后发送该广播
filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
this.registerReceiver(receiver, filter);

/**
 * 定义广播接收器
 */
private final BroadcastReceiver receiver = 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);
      if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
        bluetoothDevices.add(device.getName() + ":" + device.getAddress());
        arrayAdapter.notifyDataSetChanged();//更新适配器
      }

    } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
      //已搜素完成
    }
  }
};

//如果当前在搜索，就先取消搜索
if (mBluetoothAdapter.isDiscovering()) {
  mBluetoothAdapter.cancelDiscovery();
}
//开启搜索
mBluetoothAdapter.startDiscovery();

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
  String s = arrayAdapter.getItem(position);
  String address = s.substring(s.indexOf(":") + 1).trim();//把地址解析出来
  //主动连接蓝牙服务端
  try {
    //判断当前是否正在搜索
    if (mBluetoothAdapter.isDiscovering()) {
      mBluetoothAdapter.cancelDiscovery();
    }
    try {
      if (device == null) {
        //获得远程设备
        device = mBluetoothAdapter.getRemoteDevice(address);
      }
      if (clientSocket == null) {
        //创建客户端蓝牙Socket
        clientSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
        //开始连接蓝牙，如果没有配对则弹出对话框提示我们进行配对
        clientSocket.connect();
        //获得输出流（客户端指向服务端输出文本）
        os = clientSocket.getOutputStream();
      }
    } catch (Exception e) {
    }
    if (os != null) {
      //往服务端写信息
      os.write("蓝牙信息来了".getBytes("utf-8"));
    }
  } catch (Exception e) {
  }
}

private BluetoothAdapter mBluetoothAdapter;
private AcceptThread acceptThread;
private final UUID MY_UUID = UUID
    .fromString("abcd1234-ab12-ab12-ab12-abcdef123456");//和客户端相同的UUID
private final String NAME = "Bluetooth_Socket";
private BluetoothServerSocket serverSocket;
private BluetoothSocket socket;
private InputStream is;//输入流

private Handler handler = new Handler() {
  public void handleMessage(Message msg) {
    Toast.makeText(getApplicationContext(), String.valueOf(msg.obj),
        Toast.LENGTH_LONG).show();
    super.handleMessage(msg);
  }
};

//服务端监听客户端的线程类
private class AcceptThread extends Thread {
  public AcceptThread() {
    try {
      serverSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
    } catch (Exception e) {
    }
  }
  public void run() {
    try {
      socket = serverSocket.accept();
      is = socket.getInputStream();
      while(true) {
        byte[] buffer =new byte[1024];
        int count = is.read(buffer);
        Message msg = new Message();
        msg.obj = new String(buffer, 0, count, "utf-8");
        handler.sendMessage(msg);
      }
    }
    catch (Exception e) {
    }
  }
}

mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
acceptThread = new AcceptThread();
acceptThread.start();