Android語音識別服務空指針異常

Question

我試圖按照以下示例創建android語音識別服務：

Android語音識別連續服務

下面是我的代碼：

public class MainActivity extends Activity {

    private int mBindFlag;
    Messenger mServiceMessenger;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Context activityContext = getApplicationContext();
        Intent service = new Intent(activityContext, VoiceCommandService.class);
        activityContext.startService(service);
        mBindFlag = Build.VERSION.SDK_INT < Build.VERSION_CODES.ICE_CREAM_SANDWICH ? 0 : Context.BIND_ABOVE_CLIENT;
    }

    private final ServiceConnection mServiceConnection = new ServiceConnection()
    {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service)
        {
            //if (DEBUG) {Log.d(TAG, "onServiceConnected");} //$NON-NLS-1$

            mServiceMessenger = new Messenger(service);
            Message msg = new Message();
            msg.what = VoiceCommandService.MSG_RECOGNIZER_START_LISTENING; 
            VoiceCommandService voiceCommandService = new VoiceCommandService();
            try
            {
                voiceCommandService.mServerMessenger.send(msg);
            } 
            catch (RemoteException e)
            {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name)
        {
           //if (DEBUG) {Log.d(TAG, "onServiceDisconnected");} //$NON-NLS-1$
            mServiceMessenger = null;
        }

    };
    @Override
    protected void onStart()
    {
        super.onStart();

        bindService(new Intent(this, VoiceCommandService.class), mServiceConnection, mBindFlag);
    }

    public class VoiceCommandService extends Service
    {
    protected AudioManager mAudioManager; 
    protected SpeechRecognizer mSpeechRecognizer;
    protected Intent mSpeechRecognizerIntent;
    protected final Messenger mServerMessenger = new Messenger(new IncomingHandler(this));

    protected boolean mIsListening;
    protected volatile boolean mIsCountDownOn;

    static final int MSG_RECOGNIZER_START_LISTENING = 1;
    static final int MSG_RECOGNIZER_CANCEL = 2;


    @Override
    public void onCreate()
    {
        super.onCreate();
        mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE); 
        mSpeechRecognizer = SpeechRecognizer.createSpeechRecognizer(this);
        mSpeechRecognizer.setRecognitionListener(new SpeechRecognitionListener());
        mSpeechRecognizerIntent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
        mSpeechRecognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
                                         RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
        mSpeechRecognizerIntent.putExtra(RecognizerIntent.EXTRA_CALLING_PACKAGE,
                                         this.getPackageName());
    }

    protected class IncomingHandler extends Handler
    {
        private WeakReference<VoiceCommandService> mtarget;

        IncomingHandler(VoiceCommandService target)
        {
            mtarget = new WeakReference<VoiceCommandService>(target);
        }


        @Override
        public void handleMessage(Message msg)
        {
            final VoiceCommandService target = mtarget.get();

            switch (msg.what)
            {
                case MSG_RECOGNIZER_START_LISTENING:

                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
                    {
                        // turn off beep sound  
                        target.mAudioManager.setStreamMute(AudioManager.STREAM_SYSTEM, false);
                    }
                     if (!target.mIsListening)
                     {
                         target.mSpeechRecognizer.startListening(target.mSpeechRecognizerIntent);
                         target.mIsListening = true;
                        //Log.d(TAG, "message start listening"); //$NON-NLS-1$
                     }
                     break;

                 case MSG_RECOGNIZER_CANCEL:
                      target.mSpeechRecognizer.cancel();
                      target.mIsListening = false;
                      //Log.d(TAG, "message canceled recognizer"); //$NON-NLS-1$
                      break;
             }
       } 
    } 

    // Count down timer for Jelly Bean work around
    protected CountDownTimer mNoSpeechCountDown = new CountDownTimer(5000, 5000)
    {

        @Override
        public void onTick(long millisUntilFinished)
        {
            // TODO Auto-generated method stub

        }

        @Override
        public void onFinish()
        {
            mIsCountDownOn = false;
            Message message = Message.obtain(null, MSG_RECOGNIZER_CANCEL);
            try
            {
                mServerMessenger.send(message);
                message = Message.obtain(null, MSG_RECOGNIZER_START_LISTENING);
                mServerMessenger.send(message);
            }
            catch (RemoteException e)
            {

            }
        }
    };

    @Override
    public void onDestroy()
    {
        super.onDestroy();

        if (mIsCountDownOn)
        {
            mNoSpeechCountDown.cancel();
        }
        if (mSpeechRecognizer != null)
        {
            mSpeechRecognizer.destroy();
        }
    }

    protected class SpeechRecognitionListener implements RecognitionListener
    {

        private static final String TAG = "SpeechRecognitionListener";

        @Override
        public void onBeginningOfSpeech()
        {
            // speech input will be processed, so there is no need for count down anymore
            if (mIsCountDownOn)
            {
                mIsCountDownOn = false;
                mNoSpeechCountDown.cancel();
            }               
            //Log.d(TAG, "onBeginingOfSpeech"); //$NON-NLS-1$
        }

        @Override
        public void onBufferReceived(byte[] buffer)
        {

        }

        @Override
        public void onEndOfSpeech()
        {
            //Log.d(TAG, "onEndOfSpeech"); //$NON-NLS-1$
         }

        @Override
        public void onError(int error)
        {
            if (mIsCountDownOn)
            {
                mIsCountDownOn = false;
                mNoSpeechCountDown.cancel();
            }
             mIsListening = false;
             Message message = Message.obtain(null, MSG_RECOGNIZER_START_LISTENING);
             try
             {
                    mServerMessenger.send(message);
             }
             catch (RemoteException e)
             {

             }
            //Log.d(TAG, "error = " + error); //$NON-NLS-1$
        }

        @Override
        public void onEvent(int eventType, Bundle params)
        {

        }

        @Override
        public void onPartialResults(Bundle partialResults)
        {

        }

        @Override
        public void onReadyForSpeech(Bundle params)
        {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
            {
                mIsCountDownOn = true;
                mNoSpeechCountDown.start();
                mAudioManager.setStreamMute(AudioManager.STREAM_SYSTEM, false);
            }
            //Log.d(TAG, "onReadyForSpeech"); //$NON-NLS-1$
        }

        @Override
        public void onResults(Bundle results)
        {
            //Log.d(TAG, "onResults"); //$NON-NLS-1$
            Toast.makeText(getApplicationContext(), "this is my Toast message!!! =)",
                       Toast.LENGTH_LONG).show();
        }

        @Override
        public void onRmsChanged(float rmsdB)
        {

        }

    }



    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return mServerMessenger.getBinder();
    }
    }


}

有人可以幫我找出為什么使用mTarget.AudioManager和mTarget.SpeechRecognitionIntent nullpointer異常嗎？ 我還看到我的服務OnCreate方法沒有被點擊。 能告訴我正確的方法嗎？

更新-嘗試在BindService方法中調用服務，但未在服務中調用我的Oncreate方法。 請指出什么丟失了嗎？

Answer 1

VoiceCommandService voiceCommandService = new VoiceCommandService()

不要使用new實例化服務-諸如onCreate()類的生命周期方法將不會被調用。

使用Intent 。