Android RotationSensor返回正值但没有负值？在y轴上

Question

我需要onSensorChanged（SensorEvent事件）的帮助。当设备面朝下（y轴）0到180时，我可以得到一个Toast消息。但是无法让它在（y轴）-0到-180面朝上的另一个方向上工作。非常感谢任何帮助。

感谢您的关注，

麦克

相关代码如下：

公共类MainActivity扩展Activity实现SensorEventListener {

private SensorManager mSensorManager;
private Sensor mRotationSensor;
private double[] values;
private String TAG;

private static final int SENSOR_DELAY = 500 * 1000; // 500ms
private static final int FROM_RADS_TO_DEGS = -57;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    try {
        mSensorManager = (SensorManager) getSystemService(Activity.SENSOR_SERVICE);
        mRotationSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);
        mSensorManager.registerListener(this, mRotationSensor, SENSOR_DELAY);
    } catch (Exception e) {
        Toast.makeText(this, "Hardware compatibility issue", Toast.LENGTH_LONG).show();
    }
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // TODO Auto-generated method stub
}

@Override
public void onSensorChanged(SensorEvent event) {
    if (event.sensor == mRotationSensor) {
        if (event.values.length > 4) {
            float[] truncatedRotationVector = new float[4];
            System.arraycopy(event.values, 0, truncatedRotationVector, 0, 4);
            update(truncatedRotationVector);
        } else {
             update(event.values);
        }
    }
}

private void update(float[] vectors) {
    float[] rotationMatrix = new float[9];
    SensorManager.getRotationMatrixFromVector(rotationMatrix, vectors);
    int worldAxisX = SensorManager.AXIS_X;
    int worldAxisZ = SensorManager.AXIS_Z;
    float[] adjustedRotationMatrix = new float[9];
    SensorManager.remapCoordinateSystem(rotationMatrix, worldAxisX, worldAxisZ, adjustedRotationMatrix);
    float[] orientation = new float[3];
    SensorManager.getOrientation(adjustedRotationMatrix, orientation);
    float pitch = orientation[1] * FROM_RADS_TO_DEGS;
    float roll = orientation[2] * FROM_RADS_TO_DEGS;
    ((TextView)findViewById(R.id.pitch)).setText("Pitch: "+pitch);
    ((TextView)findViewById(R.id.roll)).setText("Roll: "+roll);


    if (pitch    <= 81 && pitch    >= 50) {
        // mostly vertical
        Toast.makeText(this, "Device Face Down ", Toast.LENGTH_SHORT).show();

    }

    {

       if (pitch   < -81&& pitch    >= -50) {
        Toast.makeText(this, "Device Face Up", Toast.LENGTH_SHORT).show();





        }} }