目标c-iOS:简单的动画

Question

我想创建一个简单的动画更改alpha值：

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

好的，通过这种方式，我改变阿尔法值两秒钟，它很好，但我想要这个：当alpha为0时，动画必须在另一时间开始，以使alpha=1所以动画应该是：alpha 0->alpha 1->alpha 0->alpha 1->。。。等等，持续时间为两秒。你能帮我吗？

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，您可以执行

   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相互调用。。。

你所需要做的就是调用：

[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）并启动下一个处理程序。

或者看看这些方法：

+ setAnimationRepeatCount:
+ setAnimationRepeatAutoreverses:

Answer 4

我认为，您可以只使用一个函数（基于以前答案的函数）：

- (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

Answer 5

您创建了一个类似的ViewController

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

然后添加动画，但您是何时在视图继承（addSubview）中添加firstViewController.view的。也只是调用

[[[FirstViewController alloc] init]autorelease]

不会创建标签对象，除非您覆盖了它的init方法。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动画和完成块方法