CocoaDev

Here is some code i wrote to play around with and experiment with animation using NSTimer. I don’t know much about efficient animation, so what you see here is probably nothing ideal. But what the hell…

The Interface File:

@interface PulsingDotView : NSView { NSTimer *timer; NSColor *color; NSBezierPath *path;

NSPoint center;
double vy0, vx0, vx, vy, ax, ay, dt, tx, ty, x0, y0, radius; }

• (void)changeDot;
• (BOOL)isOpaque;

@end

I orignally wrote this code to make a circle pulse in the view, but then after a substantial bit of playing around it got changed into something else…

And the Implementation File

#import “PulsingDotView.h” #import “math.h”

@implementation PulsingDotView

• (id)initWithFrame:(NSRect)frame { self = [super initWithFrame:frame];

  y0 = 200; x0 = 200; center.x = x0; center.y = y0;

  vy0 = 10; vx0 = 20;

  ay = -500; ax = 0; dt = .1;

  radius = 2; color = [[NSColor blueColor] retain]; path = [[NSBezierPath bezierPath] retain]; [path moveToPoint:center];

  timer = [NSTimer scheduledTimerWithTimeInterval:.001 target:self selector:@selector(changeDot) userInfo:nil repeats:YES]; return self; }

• (void)drawRect:(NSRect)rect {
  NSRect dotRect;

  [[NSColor whiteColor] set]; NSRectFill([self bounds]); // Equiv to [[NSBezierPath bezierPathWithRect:[self // bounds]] fill]

  dotRect.origin.x = center.x - radius; dotRect.origin.y = center.y - radius; dotRect.size.width = 2 * radius; dotRect.size.height = 2 * radius;

  [color set]; // if you uncomment this following line (and another similar one // further down) the ball will be trailed by a line //[path stroke]; [[NSBezierPath bezierPathWithOvalInRect:dotRect] fill]; }

• (BOOL)isOpaque { return NO; }

• (void)changeDot {
  NSRect bounds;

  //These next four lines are an attempt to simulate some gravity in // the view. Standard kinematics… center.y = (y0) + (vy0 * ty) + (0.5 * ay * ty * ty); center.x = (x0) + (vx0 * tx) + (0.5 * ax * tx * tx); vy = (vy0) + (ay * ty); vx = (vx0) + (ax * tx);

  bounds = [self bounds];

  // These next four if-statements basically change the velocity of the // ball to create the bounce off of the walls.

  if ( (center.y + radius) >= bounds.size.height ) { vy0 = -vy; ty = 0; y0 = bounds.size.height - radius; }

  if ( center.y <= radius ) { vy0 = -vy; ty = 0; y0 = radius; }

  if ( (center.x + radius) >= bounds.size.width ) { vx0 = -vx; tx = 0; x0 = bounds.size.width - radius; }

  if ( center.x <= radius) { vx0 = -vx; tx = 0; x0 = radius; }

  tx += dt; ty += dt;

  // The other line to uncomment to have a line trail the bouncing ball //[path lineToPoint:center]; [self setNeedsDisplay:YES]; }

@end

This view is just hooked up to a view in interface builder. Have fun!

Would be better to only update the dirty area instead of the whole view. :/

Here’s what I’ve tossed together…

The Interface Files:

@protocol Animation

• (BOOL)animates;
• (void)animateOneFrame;

@end

@interface AnimatingView : NSView { NSTimer *animTimer; }

• (void)animateOneFrame;

@end

Implementation File:

@implementation AnimatingView

• (void)dealloc { [animTimer invalidate]; // Don’t need this anymore [super dealloc]; }

• (id)initWithFrame:(NSRect)rect { self = [super initWithFrame:rect];

     animTimer = [NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(animateOneFrame) userInfo:nil repeats:YES];
  

  return self; }

• (void)animateOneFrame { NSArray *subs = [self subviews]; id view; int i=0;

        for (;i<[subs count];i++) {
            view = [subs objectAtIndex:i];
                  
                if ([view conformsToProtocol:@protocol(Animation)])
                    if ([view animates])
                            [view animateOneFrame];
        } } @end
  

I set my window’s contentView to be an instance of AnimatingView and load on some custom views/controls that conform to the Animation protocol.

Here’s an example of a view that conforms to the Animation protocol (Compiled here);

#import “Animation.h”

@interface BouncingView : NSView { float verticalSpeed; }

• (BOOL)animates;
• (void)animateOneFrame; @end

// BouncingView.m…

@implementation BouncingView

• (void)awakeFromNib { verticalSpeed = 0.9; // whatever. }

• (BOOL)animates { // if (someCondition) return NO;

  return YES; }

• (void)animateOneFrame { NSRect frame = [self frame]; NSRect oldFrame = frame; id superview = [self superview];

  if (frame.origin.y <= 0) { verticalSpeed = verticalSpeed-1; } if (frame.origin.y+frame.size.height >= NSMaxY([superview frame])) { verticalSpeed = verticalSpeed-1; }

     // erase where we were..
    [superview setNeedsDisplayInRect:oldFrame];
     // draw where we are..
    [superview setNeedsDisplayInRect:frame]; } @end