Question

I am trying to create a button with CoreGraphics on monotouch. I can’t figure out how to change the buttons color when its pushed. I tried overriding the TouchesBegan and TouchesEnded methods but I can’t figure out how to change the color.

Answer 1

You could handle the background color two ways. You can simply set the BackgroundColor property. This should automatically change the color. Or if you are storing the color as a private variable to be used for FillRect, you need to call SetNeedsDisplay to force a call to Draw.

public override void TouchesBegan (MonoTouch.Foundation.NSSet touches, UIEvent evt)
{
    base.TouchesBegan (touches, evt);
    this.BackgroundColor = UIColor.Green;
    backColor2 = UIColor.Yellow;
    this.SetNeedsDisplay ();
}

public override void TouchesEnded (MonoTouch.Foundation.NSSet touches, UIEvent evt)
{
    base.TouchesEnded (touches, evt);
    this.BackgroundColor = UIColor.Red;
    backColor2 = UIColor.Blue;
    this.SetNeedsDisplay ();
}

public override void Draw (RectangleF rect)
{
    base.Draw (rect);

    using (CGContext context = UIGraphics.GetCurrentContext ()) {
        RectangleF rect2 = this.Bounds;
        rect2.X += 10;
        rect2.Y += 5;
        rect2.Width -= 20;
        rect2.Height -= 10;

        backColor2.SetFill ();
        context.FillRect (rect2);
    }
}