iOS：简单的动画

Question

我想创建一个更改alpha值的简单动画：

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:2];
[view1 setAlpha:0.00];
[UIView commitAnimations];

好的，这样我将alpha值更改为两秒并且它工作正常，但我想要这样的事情：当alpha为0时，动画必须再次开始alpha = 1所以动画应该是：alpha 0 - > alpha 1 - > alpha 0 - > alpha 1 - > ...依此类推，持续时间为2秒。 你能帮助我吗？

我的完整代码是

-(IBAction){
FirstViewController *firstViewController = [[[FirstViewController alloc] init]autorelease];
[firstViewController.label1 setAlpha:1.00];
[firstViewController.label2 setAlpha:1.00];
view = firstViewController.viewFirst; //this is my view and I copy in other view
[self fadeOut:nil finished:nil context:nil];}

- (void) fadeOut:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {


[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:2];
[UIView  setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(fadeIn:finished:context:) ];
[view setAlpha:0.00];
[UIView commitAnimations];
}

- (void) fadeIn:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:2];
[UIView  setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(fadeOut:finished:context:) ];
[view setAlpha:1.00];
[UIView commitAnimations];
}

Answer 1

在iOS 4及更高版本中，您可以这样做

   view1.alpha = 1.0;
   [UIView animateWithDuration:2.0
                          delay:0.0
                        options:UIViewAnimationOptionRepeat|UIViewAnimationAutoReverse
                     animations:^{
                        view1.alpha = 0.0;
                     }
                     completion:nil
   ];

Answer 2

- (void) fadeOut:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:2];
    [UIView  setAnimationDelegate:self];
    if(animationRunning){
        [UIView setAnimationDidStopSelector:@selector(fadeIn:finished:context:) ];
    }
    [view1 setAlpha:0.00];
    [UIView commitAnimations];
}

- (void) fadeIn:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:2];
    [UIView  setAnimationDelegate:self];
    if(animationRunning){
        [UIView setAnimationDidStopSelector:@selector(fadeOut:finished:context:) ];
    }
    [view1 setAlpha:1.00];
    [UIView commitAnimations];
}

这些将在动画结束时互相调用......

你需要做的就是打电话：

[self fadeOut:nil finished:nil context:nil];

Answer 3

您可以设置动画完成处理程序（使用基于块的API或+(void)setAnimationDidStopSelector:(SEL)selector ）并启动下一个。

或者看看那些方法：

+ setAnimationRepeatCount:
+ setAnimationRepeatAutoreverses:

Answer 4

您创建如下所示的ViewController

FirstViewController *firstViewController = [[[FirstViewController alloc] init]autorelease];

然后添加动画，但是什么时候在视图heirarchy（addSubview）中添加firstViewController.view。 也只是打电话

[[[FirstViewController alloc] init]autorelease]

除非您覆盖其init方法，否则不会创建标签对象。 如果在该时间点分配了标签，请尝试调试。 同样对于动画我使用uiview anitmation和完成块方法

Answer 5

我想，你可以只使用一个功能（基于以前的答案的功能）：

- (void) fadeIn:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:2];
    [UIView  setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(fadeIn:finished:context:) ];
    [view1 setAlpha:mod(1-view1.alpha)];
    [UIView commitAnimations];
}

alplha不能是负值，因此必须应用mod