android - 特性を書き込もうとすると Android BLE NullPointerException が発生する

Question

私は Android アプリ開発に不慣れで、Android デバイスを BLE デバイス (マイクロコントローラーと通信する) と通信させるのはこれが初めての試みです。目標は、値を送信することです。この場合、文字列「green」または「blue」をバイトに変換して、マイクロコントローラーに LED をオンにするように指示します。

私は Bluetooth に精通していないので、コードをまとめるのに役立つさまざまな情報源をオンラインで探しています。ここで、デバイスに接続したポイントに到達し、信号を送信しようとすると、次のエラーコードが表示されます。

java.lang.NullPointerException: com.example.andres.battle_bots.DeviceControlActivity.makeChange(DeviceControlActivity.java:366) で null オブジェクト参照に対して仮想メソッド 'boolean android.bluetooth.BluetoothGattCharacteristic.setValue(byte[])' を呼び出そうとしていますcom.example.andres.battle_bots.DeviceControlActivity.access$800(DeviceControlActivity.java:52) で com.example.andres.battle_bots.DeviceControlActivity$3.onClick(DeviceControlActivity.java:151) で

使用している変数を使用する前にインスタンス化し、例外がまだスローされているため、何が欠けているのかよくわかりません。適応しているコードを誤解している可能性があります。これまでのところ、デバイスをスキャンして接続する DeviceScanActivity と、主なデバイスの相互作用が発生してエラーが発生する DeviceControlActivity の 2 つのアクティビティがあります。コードは次のとおりです。

import android.app.Activity;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.ImageButton;
import android.widget.SeekBar;
import android.widget.SimpleExpandableListAdapter;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.UUID;



public class DeviceControlActivity extends Activity {
private final static String TAG =   DeviceControlActivity.class.getSimpleName();

public static final String EXTRAS_DEVICE_NAME = "DEVICE_NAME";
public static final String EXTRAS_DEVICE_ADDRESS = "DEVICE_ADDRESS";

private int[] RGBFrame = {0, 0, 0};
private TextView isSerial;
private TextView mConnectionState;
private TextView mDataField;
private String mDeviceName;
private String mDeviceAddress;
//  private ExpandableListView mGattServicesList;
private BluetoothLeService mBluetoothLeService;
private boolean mConnected = false;
private BluetoothGattCharacteristic characteristicTX;
private BluetoothGattCharacteristic characteristicRX;


public final static UUID HM_RX_TX =
        UUID.fromString(SampleGattAttributes.HM_RX_TX);

private final String LIST_NAME = "NAME";
private final String LIST_UUID = "UUID";

// Code to manage Service lifecycle.
private final ServiceConnection mServiceConnection = new ServiceConnection() {

    @Override
    public void onServiceConnected(ComponentName componentName, IBinder service) {
        mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
        if (!mBluetoothLeService.initialize()) {
            Log.e(TAG, "Unable to initialize Bluetooth");
            finish();
        }
        // Automatically connects to the device upon successful start-up initialization.
        mBluetoothLeService.connect(mDeviceAddress);
    }

    @Override
    public void onServiceDisconnected(ComponentName componentName) {
        mBluetoothLeService = null;
    }
};

// Handles various events fired by the Service.
// ACTION_GATT_CONNECTED: connected to a GATT server.
// ACTION_GATT_DISCONNECTED: disconnected from a GATT server.
// ACTION_GATT_SERVICES_DISCOVERED: discovered GATT services.
// ACTION_DATA_AVAILABLE: received data from the device.  This can be a result of read
//                        or notification operations.
private final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();
        if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
            mConnected = true;
            updateConnectionState(R.string.connected);
            invalidateOptionsMenu();
        } else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
            mConnected = false;
            updateConnectionState(R.string.disconnected);
            invalidateOptionsMenu();
            clearUI();
        } else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
            // Show all the supported services and characteristics on the user interface.
            displayGattServices(mBluetoothLeService.getSupportedGattServices());
        } else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {
            displayData(intent.getStringExtra(mBluetoothLeService.EXTRA_DATA));
        }
    }
};

private void clearUI() {
//        mDataField.setText(R.string.no_data);
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final Intent intent = getIntent();
    mDeviceName = intent.getStringExtra(EXTRAS_DEVICE_NAME);
    mDeviceAddress = intent.getStringExtra(EXTRAS_DEVICE_ADDRESS);

    getActionBar().setTitle(mDeviceName);
    getActionBar().setDisplayHomeAsUpEnabled(true);
    Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
    bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);

    ImageButton U1 = (ImageButton) findViewById(R.id.up_btn1);
    U1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
            if(mBluetoothLeService != null) {
                String codeGreen = "green";
                makeChange(codeGreen);
            }
        }
    });

    ImageButton R1 = (ImageButton) findViewById(R.id.right_btn1);
    R1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton D1 = (ImageButton) findViewById(R.id.down_btn1);
    D1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton L1 = (ImageButton) findViewById(R.id.left_btn1);
    L1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton U2 = (ImageButton) findViewById(R.id.up_btn2);
    U2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mBluetoothLeService != null) {
                String codeBlue = "blue";
                makeChange(codeBlue);
            }
        }
    });

    ImageButton R2 = (ImageButton) findViewById(R.id.right_btn2);
    R2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton D2 = (ImageButton) findViewById(R.id.down_btn2);
    D2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton L2 = (ImageButton) findViewById(R.id.left_btn2);
    L2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    ImageButton BLE = (ImageButton) findViewById(R.id.ble_btn);
    BLE.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
            Intent intent = new Intent(DeviceControlActivity.this, com.example.andres.battle_bots.DeviceScanActivity.class);
            startActivity(intent);
        }
    });

    ImageButton Options = (ImageButton) findViewById(R.id.options_btn);
    Options.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Do something with Bluetooth
        }
    });

    // Sets up UI references.
   // ((TextView) findViewById(R.id.device_address)).setText(mDeviceAddress);
   // mConnectionState = (TextView) findViewById(R.id.connection_state);
    // is serial present?
   // isSerial = (TextView) findViewById(R.id.isSerial);
/*
    mDataField = (TextView) findViewById(R.id.data_value);
    mRed = (SeekBar) findViewById(R.id.seekRed);
    mGreen = (SeekBar) findViewById(R.id.seekGreen);
    mBlue = (SeekBar) findViewById(R.id.seekBlue);

    readSeek(mRed, 0);
    readSeek(mGreen, 1);
    readSeek(mBlue, 2);
*/
}

@Override
protected void onResume() {
    super.onResume();
    registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());
    if (mBluetoothLeService != null) {
        final boolean result = mBluetoothLeService.connect(mDeviceAddress);
        Log.d(TAG, "Connect request result=" + result);
    }
}

@Override
protected void onPause() {
    super.onPause();
    unregisterReceiver(mGattUpdateReceiver);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    unbindService(mServiceConnection);
    mBluetoothLeService = null;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.gatt_services, menu);
    if (mConnected) {
        menu.findItem(R.id.menu_connect).setVisible(false);
        menu.findItem(R.id.menu_disconnect).setVisible(true);
    } else {
        menu.findItem(R.id.menu_connect).setVisible(true);
        menu.findItem(R.id.menu_disconnect).setVisible(false);
    }
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.menu_connect:
            mBluetoothLeService.connect(mDeviceAddress);
            return true;
        case R.id.menu_disconnect:
            mBluetoothLeService.disconnect();
            return true;
        case android.R.id.home:
            onBackPressed();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

private void updateConnectionState(final int resourceId) {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
//                mConnectionState.setText(resourceId);
        }
    });
}

private void displayData(String data) {

    if (data != null) {
        mDataField.setText(data);
    }
}


// Demonstrates how to iterate through the supported GATT Services/Characteristics.
// In this sample, we populate the data structure that is bound to the ExpandableListView
// on the UI.
private void displayGattServices(List<BluetoothGattService> gattServices) {
    if (gattServices == null) return;
    String uuid = null;
    String unknownServiceString = getResources().getString(R.string.unknown_service);
    ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();


    // Loops through available GATT Services.
    for (BluetoothGattService gattService : gattServices) {
        HashMap<String, String> currentServiceData = new HashMap<String, String>();
        uuid = gattService.getUuid().toString();
        currentServiceData.put(
                LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));

        // If the service exists for HM 10 Serial, say so.
        if (SampleGattAttributes.lookup(uuid, unknownServiceString) == "HM 10 Serial") {
 //               isSerial.setText("Yes, serial :-)");
        } else {
//                isSerial.setText("No, serial :-(");
        }
        currentServiceData.put(LIST_UUID, uuid);
        gattServiceData.add(currentServiceData);

        // get characteristic when UUID matches RX/TX UUID
        characteristicTX = gattService.getCharacteristic(BluetoothLeService.UUID_HM_RX_TX);
        characteristicRX = gattService.getCharacteristic(BluetoothLeService.UUID_HM_RX_TX);
    }

}

private static IntentFilter makeGattUpdateIntentFilter() {
    final IntentFilter intentFilter = new IntentFilter();
    intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
    intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
    intentFilter.addAction(BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED);
    intentFilter.addAction(BluetoothLeService.ACTION_DATA_AVAILABLE);
    return intentFilter;
}

// on change of bars write char
private void makeChange(String str) {
    Log.d(TAG, "Sending result=" + str);
    final byte[] tx = str.getBytes();
    if (mConnected) {
        characteristicTX.setValue(tx);
        mBluetoothLeService.writeCharacteristic(characteristicTX);
        mBluetoothLeService.setCharacteristicNotification(characteristicRX, true);
        Log.d(TAG,"Success");
    }
    else
    {
        Log.d(TAG,"Failed");
    }
}
}

どんな助けでも大歓迎です。あなたは確かに私の人生を楽にし、Android/Bluetooth 開発を始めている他の人を助けるかもしれません. ありがとう！

android - 特性を書き込もうとすると Android BLE NullPointerException が発生する

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