Question

I have some code here in C#

   //take a world Vector2D and make it a relative Vector2D
    public Vector2D WorldToRelative(Vector2D world)
    {
        Matrix mat = new Matrix();
        PointF[] Vectors = new PointF[1];

        Vectors[0].X = world.X;
        Vectors[0].Y = world.Y;

        mat.Rotate(-m_angle / (float)Math.PI * 180.0f);
        mat.TransformVectors(Vector2Ds);

        return new Vector2D(Vectors[0].X, Vectors[0].Y);
    }

The problem is android’s Matrix does not seem to have rotate and transform vector.

It has pre and post rotation and mapping vectors.

What could I do to correctly port this code to android?

Thanks

Answer 1

Android has a great Matrix class; just use mMatrix.setRotate() and mMatrix.setTranslate() to do your rotation and translation. If you need to scale, use mMatrix.setScale().

A lot of Android functions prefix with ‘set’, so .rotate() becomes .setRotate(). It just takes a little getting used to!