Question

我想用指南针在我的应用程序中显示西方向。无论我的用户在哪里，我的指南针总是会向西方向导航。我很困惑，我怎样才能在一个方向上实现和旋转我的图像。以下是我的代码 -

public class Compass implements SensorEventListener {
    private static final String TAG = "Compass";

    private SensorManager sensorManager;
    private Sensor gsensor;
    private Sensor msensor;
    private float[] mGravity = new float[3];
    private float[] mGeomagnetic = new float[3];
    private float azimuth = 0f;
    private float currectAzimuth = 0;
    private Context context ;


    PackageManager packageManager ;
    // compass arrow to rotate
    public ImageView arrowView = null;

    public Compass(Context context) {
         this.context = context;
        sensorManager = (SensorManager) context
                .getSystemService(Context.SENSOR_SERVICE);
        gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
        packageManager = context.getPackageManager();

    }

    public void start() {
        if(packageManager.hasSystemFeature(PackageManager.FEATURE_SENSOR_COMPASS)){
            sensorManager.registerListener(this, gsensor,
                    SensorManager.SENSOR_DELAY_GAME);
            sensorManager.registerListener(this, msensor,
                    SensorManager.SENSOR_DELAY_GAME);
        }
        else{
            Toast.makeText(context,"No Compass Sensor !", Toast.LENGTH_SHORT).show();
        }

    }

    public void stop() {
        sensorManager.unregisterListener(this);
    }

    private void adjustArrow() {
        if (arrowView == null) {
            Log.i(TAG, "arrow view is not set");
            return;
        }

        Log.i(TAG, "will set rotation from " + currectAzimuth + " to "
                + azimuth);

        Animation an = new RotateAnimation(-currectAzimuth, -azimuth,
                Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
                0.5f);
        currectAzimuth = azimuth;

        an.setDuration(500);
        an.setRepeatCount(0);
        an.setFillAfter(true);

        arrowView.startAnimation(an);
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        final float alpha = 0.97f;

        synchronized (this) {
            if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

                mGravity[0] = alpha * mGravity[0] + (1 - alpha)
                        * event.values[0];
                mGravity[1] = alpha * mGravity[1] + (1 - alpha)
                        * event.values[1];
                mGravity[2] = alpha * mGravity[2] + (1 - alpha)
                        * event.values[2];

                // mGravity = event.values;

                // Log.e(TAG, Float.toString(mGravity[0]));
            }

            if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
                // mGeomagnetic = event.values;

                mGeomagnetic[0] = alpha * mGeomagnetic[0] + (1 - alpha)
                        * event.values[0];
                mGeomagnetic[1] = alpha * mGeomagnetic[1] + (1 - alpha)
                        * event.values[1];
                mGeomagnetic[2] = alpha * mGeomagnetic[2] + (1 - alpha)
                        * event.values[2];
                // Log.e(TAG, Float.toString(event.values[0]));

            }

            float R[] = new float[9];
            float I[] = new float[9];
            boolean success = SensorManager.getRotationMatrix(R, I, mGravity,
                    mGeomagnetic);
            if (success) {
                float orientation[] = new float[3];
                SensorManager.getOrientation(R, orientation);
                 Log.d(TAG, "azimuth (rad): " + azimuth);
                azimuth = (float) Math.toDegrees(orientation[0]); // orientation
                azimuth = (azimuth + 360) % 360;
                 Log.d(TAG, "azimuth (deg): " + azimuth);
                adjustArrow();
            }
        }
    }

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

Answer 1

为什么不使用三角法计算基于北纬0度的图像的正确角度。

如果北方为0度，则西方将为-90度或270度。那么只需将图像的旋转设置为北+ 270度？

如何从Android中的指南针传感器获取西向？

1 个答案: