Sensor Activity in android

问题:

I am using the following class to read accelerometer data from an android mobile:

public class AccelerometerData extends Activity implements SensorEventListener {

    //variables

    public AccelerometerData()
    {

        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
    }

    @Override
    protected void onPause() {
        super.onPause();
        mSensorManager.unregisterListener(this);
    }

    @Override
    protected void onResume() {
        super.onResume();
        mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        // TODO: my codes

        }
    }
}

Now from my main activity class, I was calling that class to read the data

AccelerometerData sbt = new AccelerometerData ();

and it shows the following message Unfortunately AccelerometerData has stopped. I am new in android development and not sure what is wrong here.

Any help would be highly appreciated.

回答1:

The answer you're looking for might look a little something like this. The MainActivity owns the AccelerometerData class.

public class MainActivity extends Activity {
  priavte AccelerometerData ad;
  private TextView someTextView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    // "this" allows 'ad' to make calls back to the MainActivity
    ad = new AccelerometerData((SensorManager)getSystemService(SENSOR_SERVICE), this);
    someTextView = (TextView)findViewById(R.id.my_text_view);
  }

  protected void onResume() {
    super.onResume();
    sensorHandler.onResume();
  }

  protected void onPause() {
    super.onPause();
    sensorHandler.onPause();
  }

  protected void setTextViewValue(float[] values){
    someTextView.setText( Float.toString(values[0]) );
  }

Then in AccelerometerData class it might look something like this.

public class AccelerometerData implements SensorEventListener {

  private final SensorManager mSensorManager;
  private final Sensor mAccelerometer;
  private final MainActivity ma;

public AccelerometerData(SensorManager sm, MainActivity ma){
    mSensorManager = sm;
    mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    this.ma = ma
}

protected void onResume() {
    mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}

protected void onPause() {
    mSensorManager.unregisterListener(this);
}

public void onAccuracyChanged(Sensor sensor, int accuracy) {
}

public void onSensorChanged(SensorEvent event) {
  // Here we call a method in MainActivity and pass it the values from the SensorChanged event
  ma.setTextViewValue( event.values );
}

}

回答2:

Your class shouldn't extend Activity. It doesn't need to. It should be owned by an activity of some sort instead.