Android中的磁传感器和图像旋转

Question

trying to build an magnetic compass, I have the following code.

public void onSensorChanged(SensorEvent event) {
    imageCompass = (ImageView) findViewById(R.id.imageMapDrawView);
    Bitmap myImg = BitmapFactory.decodeResource(getResources(), R.drawable.compass);
    Matrix matrix = new Matrix();
    matrix.postRotate(event.values[0] );
    Bitmap rotated = Bitmap.createBitmap(myImg, 0, 0, myImg.getWidth(), myImg.getHeight(),
            matrix, true);
    imageCompass.setImageBitmap(rotated);
}

I have the following questions, A. I guess event.values[0] is in degree? not in radian? B. I want to get the image from image view and rotate it around the center of the image, where I am telling that? C. I want to draw another image (an indicator on top of that Image), can I do this? I have already an compass image in the image view and I want to draw another image on top. I can't redraw whole view. How can I achieve it?

Answer 1

A. Check http://developer.android.com/reference/android/hardware/SensorEvent.html .

The length and contents of the values array depends on which sensor type is being monitored.

Sensor.TYPE_ACCELEROMETER is in m/s²
Sensor.TYPE_MAGNETIC_FIELD is in uT (micro Tesla)
Sensor.TYPE_GYROSCOPE is in rad/s

and go on for all sensors (check the link).

Also, interface SensorListener is Deprecated since API level 3. You should use SensorEventListener instead.

B and C. You should consider using OpenGL ES for drawing your images. Specially OpenGL ES 2.0 gives you so much details and ways manipulate your images that would be easy to do let you do about anything you need.