UIView scaling during animation

Question

I\'ve got a custom UIView to show a tiled image.

    - (void)drawRect:(CGRect)rect
    {
        ...
        CGContextRef context = UIGraphicsGetCurrentConte         


        

Answer 1

If it is not a big animation or performance isn't an issue for the animation duration, you can use a CADisplayLink. It does smooth out the animation of the scaling of a custom UIView drawing UIBezierPaths for instance. Below is a sample code you can adapt for your image.

The ivars of my custom view contains displayLink as a CADisplayLink, and two CGRects: toFrame and fromFrame, as well as duration and startTime.

- (void)yourAnimationMethodCall
{
    toFrame = 
    fromFrame = self.frame; // current frame.

    [displayLink removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; // just in case    
    displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(animateFrame:)];
    startTime = CACurrentMediaTime();
    duration = 0.25;
    [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
}

- (void)animateFrame:(CADisplayLink *)link
{
    CGFloat dt = ([link timestamp] - startTime) / duration;

    if (dt >= 1.0) {
        self.frame = toFrame;
        [displayLink removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
        displayLink = nil;
        return;
    }

    CGRect f = toFrame;
    f.size.height = (toFrame.size.height - fromFrame.size.height) * dt + fromFrame.size.height;
    self.frame = f;
}

Note that I haven't tested its performance, but it does work smoothly.