android - How To Create a Rotating Wheel Control?

Question

I am trying to implement the Rotatory wheel in android, just like the image displayed below.I came across the tutorial from this link. But i want to implement just as shown in the below image.The wheel consists of individual images.Does anybody have any idea regarding this implementation?? Any help would be appreciated.

Thanks in advance.

Akash

Answer 1

To do this from scratch, you would need a way to transform your touch coordinates, into polar coordinates (to have the rotation angle). This can be done easily like this:

private float cartesianToPolar(float x, float y) {
  return (float) -Math.toDegrees(Math.atan2(x - 0.5f, y - 0.5f));
}

To rotate the imageview, or the element you are using to display your knob, you can use a matrix like this:

Matrix matrix=new Matrix();
ivRotor.setScaleType(ScaleType.MATRIX);   
matrix.postRotate((float) deg, m_nWidth/2, m_nHeight/2);//getWidth()/2, getHeight()/2);
ivRotor.setImageMatrix(matrix);

Where deg is the angle and ivRobor is the knob imageview.

A complete working sample for Android, is available on Google code at: https://code.google.com/p/android-rotaryknob-view/