Building Cocoa Applications: A Step by Step Guide

Putting It All Together

In the remainder of this chapter, we’ll implement the MathAnimation view, as well as a special surprise.

1. Insert the statements shown here in bold into the MathAnimation.h file:

   #import <Cocoa/Cocoa.h>
   
   @interface MathAnimation : NSView
   {    float theta;       // Current rotation for the star
                            float fraction;    // Current intensity for the pulsing icon
                            float ddelta;      // Density delta for icon
                            NSMutableAttributedString *str;   // "MathPaper" string
                            NSImage *image;
                            NSTimer *timer;                   // Our timer
   }
   - (IBAction)tick:(id)sender;
   
   @end

The purpose of these six instance variables is easier to understand with the About panel from Figure 14-1 in mind, so you might want to go back and take a quick look at it. The first three variables, theta, fraction, and ddelta, will be used to keep track of the animation’s rotation, intensity, and density, respectively. They will be updated by NSTimer methods as they are invoked. The NSMutableAttributedString variable str will be used to hold the attributed “MathPaper” text. We’ll create this string when the MathAnimation view is first initialized, and then draw it on the view each time that we are asked to draw the view. The same is true for the image held in the NSImage instance variable, image. Finally, the NSTimer variable timer will be used to keep track of the timer. This timer is created when the window is exposed. We need to keep the instance variable so we can invalidate the timer when the window is closed.

1. Edit the file MathAnimation.m ...