通过在Android和Arduino之间传输数据来解决蓝牙问题

Question

As you can see I made an app which sends data from an Android device to a Bluetooth module. Everything works perfectly except for one little thing: every time I want to open the app I should've already turned on Bluetooth through my phone settings or the app will crash, and I have to reopen it after turning on Bluetooth so it will run properly.

I've designed a Bluetooth click listener button myself but it still crashes while I enable it via button.

Can you help me find the mistake in my code?

public class MainActivity extends AppCompatActivity {
  private static final String TAG = "bluetooth1";
  Button btnsend ;
  EditText edttext ;
  Button btnOnOff;
  private BluetoothAdapter btAdapter = null;
  private BluetoothSocket btSocket = null;
  private OutputStream outStream = null;
  // SPP UUID service
  private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
  // MAC-address of Bluetooth module (you must edit this line)
  private static String address = "20:16:06:28:17:83";
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btnsend = (Button) findViewById(R.id.btnsend);
    edttext = (EditText) findViewById(R.id.edttxt);
    btnOnOff = (Button) findViewById(R.id.btnOnOff);
    btAdapter = BluetoothAdapter.getDefaultAdapter();
    btnOnOff.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View view) {
        if (btAdapter.isEnabled()) {
          btAdapter.disable();
          Toast.makeText(getApplicationContext(), " Disabling Bluetooth", Toast.LENGTH_SHORT).show();
        } else {
          Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
          startActivityForResult(enableBtIntent,1);
          Toast.makeText(getApplicationContext(), " Enabling Bluetooth", Toast.LENGTH_SHORT).show();
        }
      }
    });
    edttext.setInputType(InputType.TYPE_CLASS_NUMBER | InputType.TYPE_NUMBER_VARIATION_PASSWORD);
    edttext.setTransformationMethod(new NumericKeyBoardTransformationMethod());
    btnsend.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View view) {
        String dataTransmit =  edttext.getText().toString();
        if (dataTransmit != null) {
          sendData(dataTransmit);
        } else {
          Toast.makeText(getApplicationContext(), "Please type something first", Toast.LENGTH_SHORT).show();
        }
      }
    });
  }

  private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
    if(Build.VERSION.SDK_INT >= 10) {
      try {
        final Method  m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", new Class[] { UUID.class });
        return (BluetoothSocket) m.invoke(device, MY_UUID);
      } catch (Exception e) {
        Toast.makeText(getBaseContext(), "Could not Insecure", Toast.LENGTH_SHORT).show();
      }
    }
    return  device.createRfcommSocketToServiceRecord(MY_UUID);
  }
  @Override
  public void onResume() {
    super.onResume();
    // Set up a pointer to the remote node using it's address.
    BluetoothDevice device = btAdapter.getRemoteDevice(address);
    // Two things are needed to make a connection:
    //   A MAC address, which we got above.
    //   A Service ID or UUID.  In this case we are using the
    //     UUID for SPP.
    try {
      btSocket = createBluetoothSocket(device);
    } catch (IOException e1) {
      errorExit("Fatal Error", "In onResume() and socket create failed: " + e1.getMessage() + ".");
    }
    btAdapter.cancelDiscovery();
    // Establish the connection. This will block until it connects.
    Toast.makeText(getBaseContext(), "Connecting", Toast.LENGTH_SHORT).show();
    try {
      btSocket.connect();
      Toast.makeText(getBaseContext(), "Connecting Ok", Toast.LENGTH_SHORT).show();
    } catch (IOException e) {
      try {
        btSocket.close();
      } catch (IOException e2) {
        errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
      }
    }
    // Create a data stream so we can talk to server.
    try {
      outStream = btSocket.getOutputStream();
    } catch (IOException e) {
      errorExit("Fatal Error", "In onResume() and output stream creation failed:" + e.getMessage() + ".");
    }
  }
  @Override
  public void onPause() {
    super.onPause();
    if (outStream != null) {
      try {
        outStream.flush();
      } catch (IOException e) {
        errorExit("Fatal Error", "In onPause() and failed to flush output stream: " + e.getMessage() + ".");
      }
    }
    try {
      btSocket.close();
    } catch (IOException e2) {
      errorExit("Fatal Error", "In onPause() and failed to close socket." + e2.getMessage() + ".");
    }
  }
  private void errorExit(String title, String message) {
    Toast.makeText(getBaseContext(), title + " - " + message, Toast.LENGTH_LONG).show();
    finish();
  }

  private void sendData(String message) {
    byte[] msgBuffer = message.getBytes();
    try {
      outStream.write(msgBuffer);
    } catch (IOException e) {
      String msg = "In onResume() and an exception occurred during write: " + e.getMessage();
      if (address.equals("20:16:06:28:17:83"))
        msg = msg + ".\n\nUpdate your server address from 20:16:06:28:17:83 to the correct address on line 35 in the java code";
      msg = msg +  ".\n\nCheck that the SPP UUID: " + MY_UUID.toString() + " exists on server.\n\n";
      errorExit("Fatal Error", msg);
    }
  }
}

Answer 1

You have to check if BT is enabled. Try with this:

protected void checkBTState() {
    mBtAdapter = BluetoothAdapter.getDefaultAdapter();
    if(mBtAdapter == null) {
        String message = getResources().getText(R.string.bluetooth_not_supported).toString();
        Toast.makeText(getBaseContext(), message, Toast.LENGTH_SHORT).show();
    } else {
        if (mBtAdapter.isEnabled()) {
            Log.d(TAG, "...Bluetooth ON...");
        } else {
            // Prompt user to turn on Bluetooth //
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, 1);
        }
    }
}

Put it in onResume

@Override
public void onResume() {
    super.onResume();
    checkBTState();
    // ...
    // some code
    // ...        
}