// 获取本地蓝牙适配器
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

// 判断手机是否支持蓝牙
 if (mBluetoothAdapter == null) {
  Toast.makeText(this, "设备不支持蓝牙", Toast.LENGTH_SHORT).show();
  finish();
 }
 // 判断是否打开蓝牙
 if (!mBluetoothAdapter.isEnabled()) {
  // 弹出对话框提示用户是后打开
  Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
  startActivityForResult(intent, 1);
  // 不做提示，强行打开
  // mBluetoothAdapter.enable();
 }else {
  // 不做提示，强行打开
   mBluetoothAdapter.enable();
 }

// 获取已经配对的设备
 Set<BluetoothDevice> pairedDevices = mBluetoothAdapter
   .getBondedDevices();
 // 判断是否有配对过的设备
 if (pairedDevices.size() > 0) {
  for (BluetoothDevice device : pairedDevices) {
   // 遍历
   mDevicesList.add(device.getAddress());
   tvDevices.append(device.getName() + ":" + device.getAddress() + "\n");
  }
 }

// 找到设备的广播
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
// 注册广播
registerReceiver(receiver, filter);
// 搜索完成的广播
filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
// 注册广播
registerReceiver(receiver, filter);

 private void scanBluth() {
// 设置进度条
setProgressBarIndeterminateVisibility(true);
setTitle("正在搜索...");
// 判断是否在搜索,如果在搜索，就取消搜索
if (mBluetoothAdapter.isDiscovering()) {
mBluetoothAdapter.cancelDiscovery();
}
// 开始搜索
mBluetoothAdapter.startDiscovery();
}

 private final BroadcastReceiver receiver = new BroadcastReceiver() {
 @Override
 public void onReceive(Context context, Intent intent) {
  // 收到的广播类型
  String action = intent.getAction();
  // 发现设备的广播
  if (BluetoothDevice.ACTION_FOUND.equals(action)) {
   // 从intent中获取设备
   BluetoothDevice device = intent
     .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
   String aa = tvDevices.getText().toString() + "";
   if (aa.contains(device.getAddress())) {
    return;
   } else {
    // 判断是否配对过
    if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
     // 添加到列表
     short rssi = intent.getExtras().getShort(
       BluetoothDevice.EXTRA_RSSI);
     int iRssi = abs(rssi);
 // 将蓝牙信号强度换算为距离
     double power = (iRssi - 59) / 25.0;
     String mm = new Formatter().format("%.2f", pow(10, power)).toString();
     tvDevices.append(device.getName() + ":"
       + device.getAddress() + " ：" + mm + "m" + "\n");
    }else {
    }
   }
   // 搜索完成
  } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED
    .equals(action)) {
   // 关闭进度条
   setProgressBarIndeterminateVisibility(true);
   setTitle("搜索完成！");
   mBLHandler.sendEmptyMessageDelayed(1, 1000);
  }
 }
};

// 用于循环扫描蓝牙的hangdler
Handler mBLHandler = new Handler() {
 @Override
 public void handleMessage(Message msg) {
  super.handleMessage(msg);
  switch (msg.what) {
   case 1:
    scanBluth();
    break;
   default:
    break;
  }
 }
};

//所有手机需要的权限，蓝牙功能才能正常使用
 <uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
//部分手机（如小米等）需要将下面两个权限添加进去，蓝牙功能才能正常使用
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />