Geek Answers Handbook

Slow down and speed up animations using CoreAnimation

I'm trying to apply a slow motion effect to my application, much like the way you can slow down most of the Mac OS graphic effects if you press Shift.

My application uses CoreAnimation, so I thought it should not be a biggie: set it speedto some slower value (for example 0.1) and put it back 1as soon as I finish, and here I go.

Unfortunately, this seems to be the wrong way. Slowing works fine, however, when I want to return to normal speed, it resumes, as if the speed were 1all the time. This basically means that if I held Shift long enough as soon as I released it, the animation would instantly end.

I found a QA tech page explaining how to pause and resume animations, but I can't figure out if this is right if it doesn't completely stop the animation. I am definitely not very good at warping time.

What would be the right way to slow down and then resume animation using CoreAnimation?

Here is a useful code:

-(void)flagsChanged:(NSEvent *)theEvent
{
    CALayer* layer = self.layer;
    [CATransaction begin];
    CATransaction.disableActions = YES;
    layer.speed = (theEvent.modifierFlags & NSShiftKeyMask) ? 0.1 : 1;
    [CATransaction commit];
}
+5
source share
1 answer

A difficult problem ...

UIView. .

, ( ).

, . beginTime, currentTime, , .

- (void)initiate {
    if(!initiated) {
        [CATransaction begin];
        [CATransaction disableActions];
        [CATransaction setAnimationTimingFunction:[CAMediaTimingFunction functionWithName: kCAMediaTimingFunctionEaseInEaseOut]];
        CABasicAnimation *ba = [CABasicAnimation animationWithKeyPath:@"position"];
        ba.duration = 10.0f;
        ba.fromValue = [NSValue valueWithCGPoint:view.layer.position];
        ba.toValue = [NSValue valueWithCGPoint:CGPointMake(384, 512)];
        [view.layer addAnimation:ba forKey:@"animatePosition"];
        [CATransaction commit];
        initiated = YES;
    }
}

- (void)slow {
    [CATransaction begin];
    CABasicAnimation *old = (CABasicAnimation *)[view.layer animationForKey:@"animatePosition"];
    CABasicAnimation *ba = [CABasicAnimation animationWithKeyPath:@"position"];
    CFTimeInterval animationBegin = old.beginTime;
    CFTimeInterval currentTime = CACurrentMediaTime();
    CFTimeInterval elapsed = currentTime - animationBegin;
    ba.duration = [[old valueForKey:@"duration"] floatValue] - elapsed;
    ba.duration = [[old valueForKey:@"duration"] floatValue];
    ba.autoreverses = [[old valueForKey:@"autoreverses"] boolValue];
    ba.repeatCount = [[old valueForKey:@"repeatCount"] floatValue];
    ba.fromValue = [NSValue valueWithCGPoint:((CALayer *)[view.layer presentationLayer]).position];
    ba.toValue = [old valueForKey:@"toValue"];
    ba.speed = 0.1;
    [view.layer addAnimation:ba forKey:@"animatePosition"];
    [CATransaction commit];
}

- (void)normal {
    [CATransaction begin];
    CABasicAnimation *old = (CABasicAnimation *)[view.layer animationForKey:@"animatePosition"];
    CABasicAnimation *ba = [CABasicAnimation animationWithKeyPath:@"position"];
    CFTimeInterval animationBegin = old.beginTime;
    CFTimeInterval currentTime = CACurrentMediaTime();
    CFTimeInterval elapsed = currentTime - animationBegin;
    ba.duration = [[old valueForKey:@"duration"] floatValue] - elapsed;
    ba.autoreverses = [[old valueForKey:@"autoreverses"] boolValue];
    ba.repeatCount = [[old valueForKey:@"repeatCount"] floatValue];
    ba.fromValue = [NSValue valueWithCGPoint:((CALayer *)[view.layer presentationLayer]).position];
    ba.toValue = [old valueForKey:@"toValue"];
    ba.speed = 1;
    [view.layer addAnimation:ba forKey:@"animatePosition"];
    [CATransaction commit];
}

. 1 , , ...

+4

More articles:


All Articles