iphone – 改变正在进行的动画

你同时拥有20个云的事实并没有真正改变太多的东西,因为我认为你的意图是使用内置的动画分别为这20个云制作动画.

如果你不确定它最终会对性能产生多大的影响,你可以尝试使用内置的动画添加一堆云(大约50个),看看它们移动的缓慢程度,然后切换它out to内置动画代码和比较.

编辑：关于Stack Overflow的讨论详细介绍了如何做你要问的事情,以防你走这条路：Cancel a UIView animation?

例：

// startAnimating called once to initiate animation loop. might be stopped e.g. 
// if game is paused or such
- (void)startAnimating
{
    // displayLink = the CADisplayLink for the current animation,if any.
    if (displayLink) {
        [displayLink invalidate]; 
        [displayLink release];
    }

    displayLink = [[CADisplayLink displayLinkWithTarget:self
                                               selector:@selector(animationTick:)] 
                   retain];

    [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
}

// tick method is called at every interval; we want to update things based on 
// a delta time (duration),so that if things get bogged down and the updates 
// come less often,we don't go into slow motion
- (void)tick:(CADisplayLink *)sender
{
    CFTimeInterval duration = sender.duration;
    // here,we update the position for all the UIView objects. example:
    CGRect cloudFrame;
    for (UIView *cloud in clouds) {
        cloudFrame = cloud.frame;
        cloudFrame.origin.x += windForceX * duration;
        cloudFrame.origin.y += windForceY * duration;
        cloud.frame = cloudFrame;
    }
    // here we might update the windForceX and Y values or this might happen somewhere
    // else
}