Question

无论当前的屏幕方向（横向或纵向），我都希望获得当前的磁性方向。

我找到this示例，但它不是独立的方向，对吧？ this也没有帮助我。我也读过http://android-developers.blogspot.de/2010/09/one-screen-turn-deserves-another.html。

这是我目前采用不赞成使用的方式（简称）：

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;
        }

但最后一部分肯定是错的！在这种情况下，如何正确使用较新的方法getRotationMatrix()？（取向独立）或者我只需要根据旋转矩阵使用event.values[]数组的其他值？或者我需要'重新映射坐标'？那么that是实现这一目标的正确方法吗？

我正在为具有360°屏幕旋转和API Level 11 +的设备开发。

我知道这些问题经常被问到，但我不能将他们的答案转移到我的问题上。

Answer 1

好的，我终于设法让代码正常工作了！

首先，我注册了Sensor.TYPE_MAGNETIC_FIELD和Sensor.TYPE_GRAVITY :(像Hoan Nguyen所说的那样！）

/**
 * 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)");
    }
}

我使用SensorEventListner进行计算：

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;

            }
        }
    }
};

Answer 2

Sensor.TYPE_ORIENTATION已弃用，只有在设备持平时才有效。使用Sensor.TYPE_ORIENTATION时，方位（方位角）是设备Y-axis指向的方向。因此，如果设备保持垂直，Y-axis点用作方位的方向没有意义。只计算后置摄像头指向的方向才有意义。要找到此方向，您必须使用Sensor.TYPE_MAGNETIC_FIELD和Sensor.TYPE_GRAVITY或Sensor.TYPE_ACCELEROMETER。如果使用Sensor.TYPE_ACCELEROMETER，则必须过滤加速度计值使用这些传感器，您可以在致电getRotationMatrix之前致电remapCoordinateSystem(inR, AXIS_X, AXIS_Z, outR)然后再致电getOrientation。要获得稳定的方向，您应该保留方向的历史记录，然后计算平均值。对于使用TYPE_GRAVITY的实现，请检查Android getOrientation Azimuth gets polluted when phone is tilted

Answer 3

我认为此代码可能会对您有所帮助：

    //get orientation
private int getScreenOrientation() {
    int rotation = getWindowManager().getDefaultDisplay().getRotation();
    DisplayMetrics dm = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(dm);
    int width = dm.widthPixels;
    int height = dm.heightPixels;
    int orientation;
    // if the device's natural orientation is portrait:
    if ((rotation == Surface.ROTATION_0
            || rotation == Surface.ROTATION_180) && height > width ||
        (rotation == Surface.ROTATION_90
            || rotation == Surface.ROTATION_270) && width > height) {
        switch(rotation) {
            case Surface.ROTATION_0:
                orientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT;
                break;
            case Surface.ROTATION_90:
                orientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE;
                break;
            case Surface.ROTATION_180:
                orientation =
                    ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT;
                break;
            case Surface.ROTATION_270:
                orientation =
                    ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE;
                break;
            default:
                Log.e(TAG, "Unknown screen orientation. Defaulting to " +
                        "portrait.");
                orientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT;
                break;              
        }
    }
    // if the device's natural orientation is landscape or if the device
    // is square:
    else {
        switch(rotation) {
            case Surface.ROTATION_0:
                orientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE;
                break;
            case Surface.ROTATION_90:
                orientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT;
                break;
            case Surface.ROTATION_180:
                orientation =
                    ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE;
                break;
            case Surface.ROTATION_270:
                orientation =
                    ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT;
                break;
            default:
                Log.e(TAG, "Unknown screen orientation. Defaulting to " +
                        "landscape.");
                orientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE;
                break;              
        }
    }

    return orientation;
}

无论屏幕方向如何，如何获得正确的方位（磁方向）？

3 个答案: