为什么TYPE_STEP_COUNTER传感器不能在Motorola设备上运行？

Question

我好几天都在寻找答案而且找不到任何答案。

问题是，我制作了一个非常简单的Android应用来计算步数。它适用于索尼和LG设备，但不适用于摩托罗拉设备（试用过第二代和第三代Moto X）。

我得到“传感器或监听器为空”的消息。

这是我的代码，任何帮助将不胜感激。谢谢！

package com.xxx.yyy;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends Activity implements SensorEventListener {

    private TextView textView;
    private SensorManager mSensorManager;
    private Sensor mStepCounterSensor;
    private Sensor mStepDetectorSensor;


    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.textView);
        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        mStepCounterSensor = mSensorManager.getDefaultSensor(19,true);
//        mStepDetectorSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_STEP_DETECTOR);
    }

    protected void onResume() {
        super.onResume();
        mSensorManager.registerListener(this, mStepCounterSensor, SensorManager.SENSOR_DELAY_FASTEST);
//        mSensorManager.registerListener(this, mStepDetectorSensor, SensorManager.SENSOR_DELAY_FASTEST);
    }

    protected void onStop() {
        super.onStop();
        mSensorManager.unregisterListener(this, mStepCounterSensor);
//        mSensorManager.unregisterListener(this, mStepDetectorSensor);
    }

    public void onSensorChanged(SensorEvent event) {
        Sensor sensor = event.sensor;
        float[] values = event.values;
        int value = -1;

        if (values.length > 0) {
            value = (int) values[0];
        }

        if (sensor.getType() == Sensor.TYPE_STEP_COUNTER) {
            textView.setText("Step Counter Detected : " + value);
        } else if (sensor.getType() == Sensor.TYPE_STEP_DETECTOR) {
            // For test only. Only allowed value is 1.0 i.e. for step taken
//            textView.setText("Step Detector Detected : " + value);
        }
    }

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

}