Drawing on the canvas of a View

Sometimes using the animation and shape APIs are not enough to create the image or app that we want to create. This may be to create a game or draw a complex image.

How to do it...

Drawing to a canvas can be easily done by creating a new view that derives from View, and then overriding the OnDraw() method:

1. First, we will need our custom View instance that implements the constructors that allow us to instantiate the view from either code or a layout file:

   public class CustomView : View
   {
     public CustomView(Context context)
       : base(context) {
     }
     public CustomView(Context context, IAttributeSet attrs)
       : base(context, attrs) {
     }
     public CustomView(
       Context context, IAttributeSet attrs, int defStyle)
       : base (context, attrs, defStyle) {
     }
   }

2. Next, we override the OnDraw() method. This method draws the actual frame and will be called each time the view needs refreshing:

   protected override void OnDraw(Canvas canvas) {
     base.OnDraw(canvas);
   }

3. Drawing...