BluetoothSocket.connect() 抛出 IOException

Question

我的程序与充当服务器的嵌入式蓝牙设备连接。我成功地找到了附近的蓝牙设备，但是当我尝试连接到新设备时，我的程序在调用 BluetoothSocket.connect() 时由于 IO 异常而崩溃。我无法弄清楚发生了什么，所以如果有人可以帮助我，我将不胜感激。

我认为这可能与我随机生成的 UUID 有关，但我并不完全确定。

谢谢。

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    btnScanDevice = (Button) findViewById( R.id.scandevice );

    stateBluetooth = (TextView) findViewById( R.id.bluetoothstate );
    startBluetooth();

    listDevicesFound = (ListView) findViewById( R.id.devicesfound );
    btArrayAdapter = new ArrayAdapter<String>( AndroidBluetooth.this,
            android.R.layout.simple_list_item_1 );
    listDevicesFound.setAdapter( btArrayAdapter );

    CheckBlueToothState();

    btnScanDevice.setOnClickListener( btnScanDeviceOnClickListener );

    registerReceiver( ActionFoundReceiver, new IntentFilter( BluetoothDevice.ACTION_FOUND ) );

    listDevicesFound.setOnItemClickListener( new OnItemClickListener()
    {
      public void onItemClick(AdapterView<?> arg0, View arg1,int arg2, long arg3) 
      {
          myBtDevice = btDevicesFound.get( arg2 );
          try {
              btSocket = myBtDevice.createRfcommSocketToServiceRecord( MY_UUID );
              iStream = btSocket.getInputStream();
              oStream = btSocket.getOutputStream();
          } catch ( IOException e ) {
              Log.e( "Bluetooth Socket", "Bluetooth not available, or insufficient permissions" );
          } catch ( NullPointerException e ) {
              Log.e( "Bluetooth Socket", "Null Pointer One" );
          }
          myBtAdapter.cancelDiscovery();
          CheckBlueToothState();
          try {
              btSocket.connect();
          } catch ( IOException e ) {
              Log.e( "Bluetooth Socket", "IO Exception" );
          } catch ( NullPointerException e ) {
              Log.e( "Bluetooth Socket", "Null Pointer Two" );
          }
      } 

  });
}

private void CheckBlueToothState() {
    if( myBtAdapter == null ) {
        stateBluetooth.setText("Bluetooth NOT supported" );
    } else {
        if( myBtAdapter.isEnabled() ) {
            if( myBtAdapter.isDiscovering() ) {
                stateBluetooth.setText( "Bluetooth is currently " +
                        "in device discovery process." );
            } else {
                stateBluetooth.setText( "Bluetooth is Enabled." );
                btnScanDevice.setEnabled( true );
            }
        } else {
            stateBluetooth.setText( "Bluetooth is NOT enabled" );
            Intent enableBtIntent = new Intent( BluetoothAdapter.ACTION_REQUEST_ENABLE );
            startActivityForResult( enableBtIntent, REQUEST_ENABLE_BT );
        }
    }
}

private Button.OnClickListener btnScanDeviceOnClickListener = new Button.OnClickListener() {
    public void onClick( View arg0 ) {
        btArrayAdapter.clear();
        myBtAdapter.startDiscovery();
    }
};


@Override
protected void onActivityResult( int requestCode, int resultCode, Intent data ) {
    if( requestCode == REQUEST_ENABLE_BT ) {
        CheckBlueToothState();
    }
}

private final BroadcastReceiver ActionFoundReceiver = new BroadcastReceiver() {
    public void onReceive( Context context, Intent intent ) {
        String action = intent.getAction();
        if( BluetoothDevice.ACTION_FOUND.equals( action ) ) {
            BluetoothDevice btDevice = intent.getParcelableExtra( BluetoothDevice.EXTRA_DEVICE );
            btDevicesFound.add( btDevice );
            btArrayAdapter.add( btDevice.getName() + "\n" + btDevice.getAddress() );
            btArrayAdapter.notifyDataSetChanged();
        }           
    }
};
public static void startBluetooth(){
    try {
        myBtAdapter = BluetoothAdapter.getDefaultAdapter();
        myBtAdapter.enable();
    } catch ( NullPointerException ex ) {
        Log.e( "Bluetooth", "Device not available" );
    }
}

public static void stopBluetooth() {
    myBtAdapter.disable();
}

Answer 1

您发布的代码有两个问题，但只有一个与您的崩溃有关。

您在 logcat 中的崩溃很可能会显示“命令被拒绝”之类的内容。 UUID 是一个必须指向嵌入式设备上已发布服务的值，它不能只是随机生成。换句话说，您要访问的 RFCOMM SPP 连接有一个特定的 UUID，它发布该 UUID 以标识该服务，并且当您创建套接字时，它必须使用匹配的 UUID。

This blog post I wrote 可以帮助您查询设备以获取需要插入程序的正确 UUID。在 Android 4.0 之前，SDK 几乎假设您提前知道它（您从蓝牙 OEM 等处获得它），因此从您的设备中发现它有点迂回。如果您有幸拥有 4.0.3 设备，fetchUuidsWithSdp() 和 getUuids() 现在是公共方法，您可以直接调用它们来查找所有已发布的服务及其关联的 UUID 值。

您的代码中可能会遇到的第二个问题是，您必须在连接后才能从套接字获取数据流，因此您可能需要像这样重写您的方法：

      myBtDevice = btDevicesFound.get( arg2 );
      try {
          btSocket = myBtDevice.createRfcommSocketToServiceRecord( MY_UUID );
      } catch ( IOException e ) {
          Log.e( "Bluetooth Socket", "Bluetooth not available, or insufficient permissions" );
      }

      myBtAdapter.cancelDiscovery();
      CheckBlueToothState();
      try {
          btSocket.connect();
          //Get streams after connect() returns without error
          iStream = btSocket.getInputStream();
          oStream = btSocket.getOutputStream();
      } catch ( IOException e ) {
          Log.e( "Bluetooth Socket", "IO Exception" );
      } catch ( NullPointerException e ) {
          Log.e( "Bluetooth Socket", "Null Pointer Two" );
      }

HTH