private Runnable update = new Runnable(){


        @Override
        public void run() {
            SearchBluetooth();
            mBluetoothAdapter.startDiscovery();
            stopCountDown();
            handler.postDelayed(this, 1000);//延遲時間
        }
    };

    private void checkBluetoothPermission() {
        if (Build.VERSION.SDK_INT >=Build.VERSION_CODES.M) {
            // Android M Permission check
            if (checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},PERMISSION_REQUEST_COARSE_LOCATION);
            }
        }
    }

    public void SearchBluetooth(){

        if(mBluetoothAdapter == null){
            Toast.makeText(this,"not find the bluetooth",Toast.LENGTH_SHORT).show();
            finish();
        }
        if(!mBluetoothAdapter.isEnabled()){
            Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(intent,1);
            Set<BluetoothDevice> myDevices = mBluetoothAdapter.getBondedDevices();
            if(myDevices.size() > 0) {
                for(BluetoothDevice device : myDevices)
                    bluetoothdeviceslist.add(device.getName()+":"+device.getAddress()+"\n");
            }
        }
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(myreceiver, filter);
        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        registerReceiver(myreceiver, filter);
    }

    public final BroadcastReceiver myreceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            //收到的廣播類型
            String action = intent.getAction();
            //發現設備的廣播
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                //從intent中獲取設備
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                int rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI,Short.MIN_VALUE);
                double txPower = -59;
                double ratio = rssi*1.0/txPower;
                if (ratio < 1.0) {
                    dis = Math.pow(ratio,10);
                }
                else {
                    dis =  (0.89976)*Math.pow(ratio,7.7095) + 0.111;
                }

                try{
                    if(device.getName().equals(ID_target)) {

                        TV1.setText(Double.toString(dis));

                    }
                }
                catch(Exception e){
                }

                /*try{
                    if(device.getName().equals(ID_target)) {
                        TV1.setText(device.getName().toString() );
                        tv2=Double.toString(dis);
                        TV2.setText(Double.toString(dis));

                    }
                }
                catch(Exception e){
                }*/
            }


        }
    };

    public void stopCountDown(){
        if(dis<1){
            timer.cancel();
        }
    }