无论屏幕方向如何，如何获得正确的方位（磁性方向）？

Question

无论当前屏幕的方向（横向或纵向）如何，我都希望获得当前的磁方向。

我找到了这个例子，但它不是方向独立的，对不对？而这也帮不了我。我确实也阅读了http://android-
developers.blogspot.de/2010/09/one-screen-turn-deserves-
another.html

。

这是我当前使用的方法，不想使用（过短的）废弃方法：

mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);

private SensorEventListener sensorEventListener = new SensorEventListener() {

    public void onSensorChanged(SensorEvent event) {

        /* Get measured value */
        float current_measured_bearing = (float) event.values[0];

        /* Compensate device orientation */
        switch (((WindowManager) getSystemService(WINDOW_SERVICE))
                .getDefaultDisplay().getRotation()) {
        case Surface.ROTATION_90:
            current_measured_bearing = current_measured_bearing + 90f;
            break;
        case Surface.ROTATION_180:
            current_measured_bearing = current_measured_bearing - 180f;
            break;
        case Surface.ROTATION_270:
            current_measured_bearing = current_measured_bearing - 90f;
            break;
        }

但是最后一部分肯定是错误的！getRotationMatrix()在这种情况下，如何正确使用更新的方法？（与方向无关）还是仅需event.values[]基于旋转矩阵使用数组的其他值？还是我需要“重新映射坐标”？那么，是实现这一目标的正确方法是什么？

我正在为屏幕旋转360°和API Level 11+的设备进行开发。

我知道这些问题经常被问到，但我无法简单地将其答案转移给我的问题。

Answer 1

好的，我终于设法使代码生效了！

首先，我注册一个Sensor.TYPE_MAGNETIC_FIELDand Sensor.TYPE_GRAVITY：（就像阮阮说的那样！）

/**
 * Initialize the Sensors (Gravity and magnetic field, required as a compass
 * sensor)
 */
private void initSensors() {

    LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    SensorManager sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
    Sensor mSensorGravity = sensorManager.getDefaultSensor(Sensor.TYPE_GRAVITY);
    Sensor mSensorMagneticField = sensorManager
            .getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

    /* Initialize the gravity sensor */
    if (mSensorGravity != null) {
        Log.i(TAG, "Gravity sensor available. (TYPE_GRAVITY)");
        sensorManager.registerListener(mSensorEventListener,
                mSensorGravity, SensorManager.SENSOR_DELAY_GAME);
    } else {
        Log.i(TAG, "Gravity sensor unavailable. (TYPE_GRAVITY)");
    }

    /* Initialize the magnetic field sensor */
    if (mSensorMagneticField != null) {
        Log.i(TAG, "Magnetic field sensor available. (TYPE_MAGNETIC_FIELD)");
        sensorManager.registerListener(mSensorEventListener,
                mSensorMagneticField, SensorManager.SENSOR_DELAY_GAME);
    } else {
        Log.i(TAG,
                "Magnetic field sensor unavailable. (TYPE_MAGNETIC_FIELD)");
    }
}

我将其SensorEventListner用于计算：

private SensorEventListener mSensorEventListener = new SensorEventListener() {

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

    @Override
    public void onSensorChanged(SensorEvent event) {

        if (event.sensor.getType() == Sensor.TYPE_GRAVITY) {

            mGravity = event.values.clone();

        } else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {

            mMagnetic = event.values.clone();

        }

        if (mGravity != null && mMagnetic != null) {

            /* Create rotation Matrix */
            float[] rotationMatrix = new float[9];
            if (SensorManager.getRotationMatrix(rotationMatrix, null,
                    mGravity, mMagnetic)) {

                /* Compensate device orientation */
                // http://android-developers.blogspot.de/2010/09/one-screen-turn-deserves-another.html
                float[] remappedRotationMatrix = new float[9];
                switch (getWindowManager().getDefaultDisplay()
                        .getRotation()) {
                case Surface.ROTATION_0:
                    SensorManager.remapCoordinateSystem(rotationMatrix,
                            SensorManager.AXIS_X, SensorManager.AXIS_Y,
                            remappedRotationMatrix);
                    break;
                case Surface.ROTATION_90:
                    SensorManager.remapCoordinateSystem(rotationMatrix,
                            SensorManager.AXIS_Y,
                            SensorManager.AXIS_MINUS_X,
                            remappedRotationMatrix);
                    break;
                case Surface.ROTATION_180:
                    SensorManager.remapCoordinateSystem(rotationMatrix,
                            SensorManager.AXIS_MINUS_X,
                            SensorManager.AXIS_MINUS_Y,
                            remappedRotationMatrix);
                    break;
                case Surface.ROTATION_270:
                    SensorManager.remapCoordinateSystem(rotationMatrix,
                            SensorManager.AXIS_MINUS_Y,
                            SensorManager.AXIS_X, remappedRotationMatrix);
                    break;
                }

                /* Calculate Orientation */
                float results[] = new float[3];
                SensorManager.getOrientation(remappedRotationMatrix,
                        results);

                /* Get measured value */
                float current_measured_bearing = (float) (results[0] * 180 / Math.PI);
                if (current_measured_bearing < 0) {
                    current_measured_bearing += 360;
                }

                /* Smooth values using a 'Low Pass Filter' */
                current_measured_bearing = current_measured_bearing
                        + SMOOTHING_FACTOR_COMPASS
                        * (current_measured_bearing - compass_last_measured_bearing);

                /* Update normal output */
                visual_compass_value.setText(String.valueOf(Math
                        .round(current_bearing))
                        + getString(R.string.degrees));

                /*
                 * Update variables for next use (Required for Low Pass
                 * Filter)
                 */
                compass_last_measured_bearing = current_measured_bearing;

            }
        }
    }
};