iOS App Development Portable Genius

Drawing Graphics with Code

You can draw graphics with code in two ways. You can use a set of drawing commands that are built into iOS views to create custom graphics. And you can create objects in your code and add them to the current view. This is similar to adding them to a view in IB, but you can control the position and appearance of objects from your code, and you’re not limited to a static layout.

Using paths, strokes, and fills

The UIView class includes a method called drawRect: that is a ready-made space for graphics commands. Shapes are defined using a class called UIBezierPath, which can be used to draw lines, boxes, circles, and ovals. You can also draw curved lines with “handles” that control the shape of an arc. And you can join paths indefinitely, so almost any shape is possible.

Paths remain invisible until you either stroke them or fill them. Stroking a path draws an outline. Filling a path fills the area inside the path. (A path should be closed before you try to fill it.)

To make drawRect: work for you, you must subclass UIView. You can follow the steps in Chapter 5 to add a new subclass of UIView to your project. You must also tell IB to use the subclass, as described in Chapter 9.

To work through this example, create a new SingleView project called ViewDrawing. Use the New File option to create a subclass of UIView called MyView. Tell IB about the subclass. Now we’ll add some code to draw some shapes.

Uncommenting drawRect:

Click your MyView.m file in the ...