Java 按下setOnTouchListener时获取传感器数据时出错

我有Android代码，按下按钮时，我正试图从手机中获取加速计数据。 这是我的代码：

public class MainActivity extends Activity implements SensorEventListener{

private SensorManager aSensorManager;
private TextView ax;
private TextView ay;
private TextView az;
private float xa ;
private float ya ;
private float za ;
public Vector<Float> vecA_x;

private Vibrator v;
long[] pattern = { 0, 200, 500 };
long cap = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
   // dataBase = DataBaseManager;
    Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
     ax = (TextView) findViewById(R.id.textView4);
     ay = (TextView) findViewById(R.id.textView5);
     az = (TextView) findViewById(R.id.textView6);
     aSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
     findViewById(R.id.button1).setOnTouchListener(new OnTouchListener() {

            public boolean onTouch(View v, MotionEvent event) {
            if(event.getAction() == MotionEvent.ACTION_DOWN){
                start();
                return true;
            }
            if(event.getAction() == MotionEvent.ACTION_UP){
                //vibe(pattern);
                onPause();
                return true;
            }
            return false;
        }
    });
}

public void onSensorChanged(SensorEvent event){
    if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER){
        float x=event.values[0]; 
        vecA_x.addElement(x); // here the error
        runAcce(event);
    }
}
}
private void vibe(long[] p){
    v.vibrate(p, -1);
}
private void runAcce(SensorEvent event){
    float[] values = event.values;
    xa = values[0];  gx.setText((xa) + "");
    ya = values[1];  gy.setText((ya) + "");
    za = values[2];  gz.setText((za) + "");


}

public void onAccuracyChanged(Sensor sensor, int accuracy){

}
private void start(){
    aSensorManager.registerListener(this, aSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),SensorManager.SENSOR_DELAY_NORMAL);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}
@Override
protected void onResume(){
    super.onResume();
}
@Override
protected void onPause(){
    super.onPause();
    aSensorManager.unregisterListener(this);
}

我不知道该怎么办，我的意思是向量是动态数组，能够捕获值。 我的问题是：如何在我的代码中获取传感器数据到向量？我应该写什么？

---

请帮帮我。

您在哪里初始化vacA\U x？

float x=event.values[0]; 
        vecA_x.addElement(x); // here the error