执行多个连续 UIView 动画的最佳方式? [英] Best Way to Perform Several Sequential UIView Animations?

问题描述

我有一系列 8 个 UIView 动画，它们在我的视图加载后直接发生.现在，我通过使用 animationDidStop:finished:context 委托方法来实现这一点，一切都按预期进行.问题是我对每个动画都有一个新方法.这些方法中的大部分代码都是重复的，只是动画持续时间和元素的实际位置发生了变化.

I have a series of 8 UIView animations that occur directly after my view is loaded. Right now, I am accomplishing this by using the animationDidStop:finished:context delegate method, and everything works as expected. The problem is that I have a new method for each animation. Most of the code in each of these methods is repeated, with only the animation duration and the actual positioning of elements changing.

我尝试创建一个将被调用的方法，并让上下文保存适当更改 UI 所需的参数，但它似乎递归调用自己远远超过我调用它的次数:

I tried to create a single method which would be called and have the context hold the parameters needed to change the UI appropriately, but it seems to be recursively calling itself well past the amount of times I call it:

-(void)animationDidStop:(NSString *)animationID finished:(BOOL)finished context:(void *)context{
    NSNumber *number = (NSNumber *)context;
    int animationStep = [number intValue];
    int nextAnimationStep = animationStep + 1;
    NSNumber *nextAnimationStepNumber = [NSNumber numberWithInt:nextAnimationStep];
    NSLog(@"Animation Step: %i", animationStep);

    CGRect firstFrame = CGRectMake(self.feedsScroll.frame.size.width * 2, 0.0f, self.secondFeedView.view.frame.size.width, self.secondFeedView.view.frame.size.height);
    CGRect thirdFrame = CGRectMake(self.feedsScroll.frame.size.width * 2, 0.0f, self.thirdFeedView.view.frame.size.width, self.thirdFeedView.view.frame.size.height);

    [UIView beginAnimations:nil context:nextAnimationStepNumber];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];
    [UIView setAnimationDelegate:self];

    if (animationStep < 8) 
        [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];

    NSLog(@"Beginning animations");

    switch (animationStep) {
        case 0:
            [UIView setAnimationDuration:.3];
            self.firstFeedView.view.center = CGPointMake(self.firstFeedView.view.center.x + 30, self.firstFeedView.view.center.y);
            break;
        case 1:
            [UIView setAnimationDuration:.3];
            self.firstFeedView.view.center = CGPointMake(self.firstFeedView.view.center.x  - 30, self.firstFeedView.view.center.y);
            break;
        case 2:
            [UIView setAnimationDuration:.3];
            [self.secondFeedView.view setFrame:firstFrame];
            break;
        case 3:
            [UIView setAnimationDuration:.3];
            self.secondFeedView.view.center = CGPointMake(self.secondFeedView.view.center.x + 30, self.firstFeedView.view.center.y);
            break;
        case 4:
            [UIView setAnimationDuration:.3];
            self.secondFeedView.view.center = CGPointMake(self.secondFeedView.view.center.x - 30, self.firstFeedView.view.center.y);
            break;
        case 5:
            NSLog(@"Animation step 6");
            [UIView setAnimationDuration:.5];
            self.firstFeedView.view.center = CGPointMake(self.firstFeedView.view.center.x - 230, self.firstFeedView.view.center.y);
            self.secondFeedView.view.center = CGPointMake(self.secondFeedView.view.center.x - 230, self.firstFeedView.view.center.y);
            break;
        case 6:
            [UIView setAnimationDuration:.5];
            [self.thirdFeedView.view setFrame:thirdFrame];
            break;
        case 7:
            [UIView setAnimationDuration:.3];
            self.thirdFeedView.view.center = CGPointMake(self.thirdFeedView.view.center.x + 30, self.firstFeedView.view.center.y);
            break;
        case 8:
            [UIView setAnimationDuration:.3];
            self.thirdFeedView.view.center = CGPointMake(self.thirdFeedView.view.center.x - 30, self.thirdFeedView.view.center.y);
            break;
        default:
            break;
    }

    [UIView commitAnimations];  
}

我知道这可能是一个幼稚的实现.我是 iPhone 开发的新手，正在寻找一些最佳实践来应用这里.我是否以错误的方式处理这个问题?

I know this is probably a naive implementation. I am new to iPhone development, and am looking for some best practices to apply here. Am I going about this in the wrong way?

推荐答案

如果您愿意升级到 iOS 4.0，新的基于块的动画方法可以使此动画链接变得微不足道.例如:

If you're willing to step up to iOS 4.0, the new blocks-based animation approach can make this animation chaining trivial. For example:

[UIView animateWithDuration:1.0 animations:^{ view.position = CGPointMake(0.0f, 0.0f); } completion:^(BOOL finished){
    [UIView animateWithDuration:0.2 animations:^{ view.alpha = 0.0; } completion:^(BOOL finished){
        [view removeFromSuperview]; }];
}]

将导致 view 在 1 秒内动画到 (0, 0)，淡出 0.2 秒，然后从其超级视图中删除.这些动画将是连续的.

will cause view to animate to (0, 0) over a duration of 1 second, fade out for 0.2 seconds, then be removed from its superview. These animations will be sequential.

+animateWithDuration:animations:completion: 类方法中的第一个块包含属性更改以立即进行动画处理，第二个块是在动画完成时要执行的操作.由于此回调可以包含另一个此类动画，因此您可以嵌套它们以创建任意动画链.

The first block in the +animateWithDuration:animations:completion: class method contains the property changes to animate at once, and the second is the action to be performed on completion of the animation. Because this callback can contain another animation of this sort, you can nest them to create arbitrary chains of animations.

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