无法通过Android应用程序向Arduino发送字符

• 我已经成功地将bletooth终端应用程序中的字符发送到Arduino,并且成功了。

• 现在,我正试图使用自己的应用程序向我的arduino发送一些字符,我已将HC05蓝牙模块编程为从属模式,以便它只能接收数据。我用了这个密码 Reference code 以蓝牙聊天为起点,以便以后我可以根据需要修改它,只将字符从android传输到arduino。

但一旦我击中 “发送”按钮 在手机上键入字符后,我的logcat中出现以下错误:

05-05 16:06:41.966 8042-8042/? E/AndroidRuntime: FATAL EXCEPTION: main
                                             Process: com.example.android.bluetoothtest, PID: 8042
                                             java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.android.bluetoothtest.BluetoothConnectionService.write(byte[])' on a null object reference
                                                 at com.example.android.bluetoothtest.MainActivity$7.onClick(MainActivity.java:227)
                                                 at android.view.View.performClick(View.java:5640)
                                                 at android.view.View$PerformClick.run(View.java:22455)
                                                 at android.os.Handler.handleCallback(Handler.java:751)
                                                 at android.os.Handler.dispatchMessage(Handler.java:95)
                                                 at android.os.Looper.loop(Looper.java:154)
                                                 at android.app.ActivityThread.main(ActivityThread.java:6165)
                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:888)
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:778)

Java文件: 主要活动。JAVA

public class MainActivity extends AppCompatActivity implements 
AdapterView.OnItemClickListener{

private static final String TAG = "MainActivity";

BluetoothAdapter mBluetoothAdapter;
Button btnEnableDisable_Discoverable;

BluetoothConnectionService mBluetoothConnection;

Button btnStartConnection;
Button btnSend;

EditText etSend;

private static final UUID MY_UUID_INSECURE =
        UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

BluetoothDevice mBTDevice;

public ArrayList<BluetoothDevice> mBTDevices = new ArrayList<>();

public DeviceListAdapter mDeviceListAdapter;

ListView lvNewDevices;


// Create a BroadcastReceiver for ACTION_FOUND
private final BroadcastReceiver mBroadcastReceiver1 = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        // When discovery finds a device
        if (action.equals(mBluetoothAdapter.ACTION_STATE_CHANGED)) {
            final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, mBluetoothAdapter.ERROR);

            switch(state){
                case BluetoothAdapter.STATE_OFF:
                    Log.d(TAG, "onReceive: STATE OFF");
                    break;
                case BluetoothAdapter.STATE_TURNING_OFF:
                    Log.d(TAG, "mBroadcastReceiver1: STATE TURNING OFF");
                    break;
                case BluetoothAdapter.STATE_ON:
                    Log.d(TAG, "mBroadcastReceiver1: STATE ON");
                    break;
                case BluetoothAdapter.STATE_TURNING_ON:
                    Log.d(TAG, "mBroadcastReceiver1: STATE TURNING ON");
                    break;
            }
        }
    }
};

/**
 * Broadcast Receiver for changes made to bluetooth states such as:
 * 1) Discoverability mode on/off or expire.
 */
private final BroadcastReceiver mBroadcastReceiver2 = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if (action.equals(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED)) {

            int mode = intent.getIntExtra(BluetoothAdapter.EXTRA_SCAN_MODE, BluetoothAdapter.ERROR);

            switch (mode) {
                //Device is in Discoverable Mode
                case BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE:
                    Log.d(TAG, "mBroadcastReceiver2: Discoverability Enabled.");
                    break;
                //Device not in discoverable mode
                case BluetoothAdapter.SCAN_MODE_CONNECTABLE:
                    Log.d(TAG, "mBroadcastReceiver2: Discoverability Disabled. Able to receive connections.");
                    break;
                case BluetoothAdapter.SCAN_MODE_NONE:
                    Log.d(TAG, "mBroadcastReceiver2: Discoverability Disabled. Not able to receive connections.");
                    break;
                case BluetoothAdapter.STATE_CONNECTING:
                    Log.d(TAG, "mBroadcastReceiver2: Connecting....");
                    break;
                case BluetoothAdapter.STATE_CONNECTED:
                    Log.d(TAG, "mBroadcastReceiver2: Connected.");
                    break;
            }

        }
    }
};




/**
 * Broadcast Receiver for listing devices that are not yet paired
 * -Executed by btnDiscover() method.
 */
private BroadcastReceiver mBroadcastReceiver3 = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();
        Log.d(TAG, "onReceive: ACTION FOUND.");

        if (action.equals(BluetoothDevice.ACTION_FOUND)){
            BluetoothDevice device = intent.getParcelableExtra (BluetoothDevice.EXTRA_DEVICE);
            mBTDevices.add(device);
            Log.d(TAG, "onReceive: " + device.getName() + ": " + device.getAddress());
            mDeviceListAdapter = new DeviceListAdapter(context, R.layout.device_adapter_view, mBTDevices);
            lvNewDevices.setAdapter(mDeviceListAdapter);
        }
    }
};

/**
 * Broadcast Receiver that detects bond state changes (Pairing status changes)
 */
private final BroadcastReceiver mBroadcastReceiver4 = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if(action.equals(BluetoothDevice.ACTION_BOND_STATE_CHANGED)){
            BluetoothDevice mDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            //3 cases:
            //case1: bonded already
            if (mDevice.getBondState() == BluetoothDevice.BOND_BONDED){
                Log.d(TAG, "BroadcastReceiver: BOND_BONDED.");
                //inside BroadcastReceiver4
                mBTDevice = mDevice;
            }
            //case2: creating a bone
            if (mDevice.getBondState() == BluetoothDevice.BOND_BONDING) {
                Log.d(TAG, "BroadcastReceiver: BOND_BONDING.");
            }
            //case3: breaking a bond
            if (mDevice.getBondState() == BluetoothDevice.BOND_NONE) {
                Log.d(TAG, "BroadcastReceiver: BOND_NONE.");
            }
        }
    }
};



@Override
protected void onDestroy() {
    Log.d(TAG, "onDestroy: called.");
    super.onDestroy();
    unregisterReceiver(mBroadcastReceiver1);
    unregisterReceiver(mBroadcastReceiver2);
    unregisterReceiver(mBroadcastReceiver3);
    unregisterReceiver(mBroadcastReceiver4);
    //mBluetoothAdapter.cancelDiscovery();
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button btnONOFF = (Button) findViewById(R.id.btnONOFF);
    btnEnableDisable_Discoverable = (Button) findViewById(R.id.btnDiscoverable_on_off);
    lvNewDevices = (ListView) findViewById(R.id.lvNewDevices);
    mBTDevices = new ArrayList<>();

    btnStartConnection = (Button) findViewById(R.id.btnStartConnection);
    btnSend = (Button) findViewById(R.id.btnSend);
    etSend = (EditText) findViewById(R.id.editText);

    //Broadcasts when bond state changes (ie:pairing)
    IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_BOND_STATE_CHANGED);
    registerReceiver(mBroadcastReceiver4, filter);

    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

    lvNewDevices.setOnItemClickListener(MainActivity.this);


    btnONOFF.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Log.d(TAG, "onClick: enabling/disabling bluetooth.");
            enableDisableBT();
        }
    });

    btnStartConnection.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startConnection();
        }
    });

    btnSend.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            byte[] bytes = etSend.getText().toString().getBytes(Charset.defaultCharset());
            mBluetoothConnection.write(bytes);
        }
    });

}

//create method for starting connection
//***remember the conncction will fail and app will crash if you haven't 
paired first
public void startConnection(){
    startBTConnection(mBTDevice,MY_UUID_INSECURE);
}

/**
 * starting chat service method
 */
public void startBTConnection(BluetoothDevice device, UUID uuid){
    Log.d(TAG, "startBTConnection: Initializing RFCOM Bluetooth Connection.");

    mBluetoothConnection.startClient(device,uuid);
}



public void enableDisableBT(){
    if(mBluetoothAdapter == null){
        Log.d(TAG, "enableDisableBT: Does not have BT capabilities.");
    }
    if(!mBluetoothAdapter.isEnabled()){
        Log.d(TAG, "enableDisableBT: enabling BT.");
        Intent enableBTIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivity(enableBTIntent);

        IntentFilter BTIntent = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
        registerReceiver(mBroadcastReceiver1, BTIntent);
    }
    if(mBluetoothAdapter.isEnabled()){
        Log.d(TAG, "enableDisableBT: disabling BT.");
        mBluetoothAdapter.disable();

        IntentFilter BTIntent = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
        registerReceiver(mBroadcastReceiver1, BTIntent);
    }

}


public void btnEnableDisable_Discoverable(View view) {
    Log.d(TAG, "btnEnableDisable_Discoverable: Making device discoverable for 300 seconds.");

    Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
    discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
    startActivity(discoverableIntent);

    IntentFilter intentFilter = new IntentFilter(mBluetoothAdapter.ACTION_SCAN_MODE_CHANGED);
    registerReceiver(mBroadcastReceiver2,intentFilter);

}

public void btnDiscover(View view) {
    Log.d(TAG, "btnDiscover: Looking for unpaired devices.");

    if(mBluetoothAdapter.isDiscovering()){
        mBluetoothAdapter.cancelDiscovery();
        Log.d(TAG, "btnDiscover: Canceling discovery.");

        //check BT permissions in manifest
        checkBTPermissions();

        mBluetoothAdapter.startDiscovery();
        IntentFilter discoverDevicesIntent = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(mBroadcastReceiver3, discoverDevicesIntent);
    }
    if(!mBluetoothAdapter.isDiscovering()){

        //check BT permissions in manifest
        checkBTPermissions();

        mBluetoothAdapter.startDiscovery();
        IntentFilter discoverDevicesIntent = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(mBroadcastReceiver3, discoverDevicesIntent);
    }
}

/**
 * This method is required for all devices running API23+
 * Android must programmatically check the permissions for bluetooth. Putting the proper permissions
 * in the manifest is not enough.
 *
 * NOTE: This will only execute on versions > LOLLIPOP because it is not needed otherwise.
 */
private void checkBTPermissions() {
    if(Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP){
        int permissionCheck = this.checkSelfPermission("Manifest.permission.ACCESS_FINE_LOCATION");
        permissionCheck += this.checkSelfPermission("Manifest.permission.ACCESS_COARSE_LOCATION");
        if (permissionCheck != 0) {

            this.requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION}, 1001); //Any number
        }
    }else{
        Log.d(TAG, "checkBTPermissions: No need to check permissions. SDK version < LOLLIPOP.");
    }
}

@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
    //first cancel discovery because its very memory intensive.
    mBluetoothAdapter.cancelDiscovery();

    Log.d(TAG, "onItemClick: You Clicked on a device.");
    String deviceName = mBTDevices.get(i).getName();
    String deviceAddress = mBTDevices.get(i).getAddress();

    Log.d(TAG, "onItemClick: deviceName = " + deviceName);
    Log.d(TAG, "onItemClick: deviceAddress = " + deviceAddress);

    //create the bond.
    //NOTE: Requires API 17+? I think this is JellyBean
    if(Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR2){
        Log.d(TAG, "Trying to pair with " + deviceName);
        mBTDevices.get(i).createBond();

        mBTDevice = mBTDevices.get(i);
        mBluetoothConnection = new BluetoothConnectionService(MainActivity.this);
    }
}

}

请帮帮我 ,我似乎根本找不到解决方案,我是个新手。

谢谢,非常感谢您的帮助。