java - 连接到 Android 上已配对的设备时提示输入蓝牙 PIN

Question

我正在开发一个 Android 应用程序来连接到支持蓝牙串行端口配置文件 (SPP) 的简单设备。我能够成功连接并交换数据，但每次连接时都会提示用户输入设备的 PIN。

在蓝牙设置中，我可以看到设备“已配对但未连接”。

提示是个问题，因为如果用户输入 PIN 的速度不够快，套接字连接会超时，用户必须重试。

相关代码如下...

@Override
protected void onCreate(Bundle savedInstanceState)
{
  super.onCreate(savedInstanceState);
  setContentView(R.layout.scanlayout);
  ...  
  _Context = this;
  _ActivityCreated = true;
  _ReceivedText = (TextView)findViewById(R.id._Scan_Results);
  _BluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  _BluetoothDevice = _BluetoothAdapter.getRemoteDevice(_DeviceAddress);
  _BusySpinner = ProgressDialog.show(_Context, "", "Connecting to scanner...");
  new ConnectToScannerTask().execute(_BluetoothDevice);
}
private final Handler scanReceivedHandler = new Handler() 
{
 @Override
 public void handleMessage(Message message) 
 {
  String receivedText = (String)message.obj;
  _ReceivedText.setText(receivedText);
 }
};

private class ConnectToScannerTask extends AsyncTask<BluetoothDevice, Void, InputStream>
{
 @Override
 protected InputStream doInBackground(BluetoothDevice... params)
 {
  BluetoothDevice device = params[0];
  try
  {
   _Socket = device.createRfcommSocketToServiceRecord(WELL_KNOWN_UUID);
   _BluetoothAdapter.cancelDiscovery();
   _Socket.connect();
   return _Socket.getInputStream();
  }
  catch (IOException e)
  {
   Log.d("ScanActivity.ConnectToScannerTask.doInBackground", e.getMessage());
  }
  return null;
 }

 @Override
 protected void onPostExecute(final InputStream result)
 {
  _BusySpinner.dismiss();

  if (result == null)
  {
   _ReceivedText.setText("Failed to connect to scanner.");
   return;
  }

      Thread thread = new Thread()
      {
       @Override
       public void run() 
       {
        byte[] buffer = new byte[1024];
     try
     {
      while (_ActivityCreated)
      {
       Arrays.fill(buffer, (byte) 0);
       int bytesRead = result.read(buffer);
       if (bytesRead > 0)
       {
        Message message = scanReceivedHandler.obtainMessage(1, new String(buffer));
        message.sendToTarget();
        Log.e("ScanActivity", "Received: " + new String(buffer));
       }
       if (bytesRead < 0)
       {
        break;
       }
      }
      Message message = scanReceivedHandler.obtainMessage(1, "End of Stream");
      message.sendToTarget();
      Log.e("ScanActivity", "End of Stream");
     }
     catch (Exception e)
     {
      Message message = scanReceivedHandler.obtainMessage(1, "Connection to scanner lost");
      message.sendToTarget();
      Log.e("ScanActivity", e.getMessage());
     }
     try
     {
      _Socket.close();
     }
     catch (IOException e)
     {
      Log.e("ScanActivity", e.getMessage());
     }
       }
      };
      thread.start();
  }
 }

只要用户快速输入PIN，连接成功，我就可以接收数据。我的直觉是我缺少设置步骤。不过，我不太熟悉 BT 的具体细节，所以我不确定这是否是设备强制输入 PIN 的问题？

Answer 1

这可能是远程设备没有保持设备绑定(bind)的问题(意味着存储链接 key 以用于后续连接)，这将导致每次重新配对并需要输入 PIN。Android 通常应在成功配对后存储绑定(bind)信息。