iOS：简单的动画

Question

I want to create a simple animation changing alpha value:

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

Ok in this way I change the alpha value for two seconds and it works fine, but I want this thing: When alpha is 0 the animation must should start another time to alpha = 1 So the animation should be: alpha 0 -> alpha 1 -> alpha 0 -> alpha 1 -> ... and so on with a duration of two seconds. Can you help me?

my complete code is

-(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

In iOS 4 and later you can do

   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];
}

These will call each other on the end of the animation...

All you need to do to start the ball rolling is call:

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

Answer 3

You can set a animation completion handler (either using the block-based API or +(void)setAnimationDidStopSelector:(SEL)selector ) and start the next one.

Alternatively have a look at those to methods:

+ setAnimationRepeatCount:
+ setAnimationRepeatAutoreverses:

Answer 4

You create a ViewController like below

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

And then adding animation to it, but when did you add firstViewController.view in view heirarchy(addSubview). Also just calling

[[[FirstViewController alloc] init]autorelease]

wont create label object unless you have override its init method. Try debugging if label is allocated at that point of time. Also for animation i use uiview anitmation with completion block method

Answer 5

I think, you can use just one function (based on previous answer's functions):

- (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];
}

The alplha must not be a negative value, so a mod must be applied