UIView Animaton重置为开始

Question

我试图运行一个动画，以便scrollview的contentoffset不断滚动下来。

但是，在每次重复之后，它将从原始位置开始动画并且不会进行。

[UIView beginAnimations:nil context:NULL]; 
[UIView setAnimationBeginsFromCurrentState: YES]; 
[UIView setAnimationDuration:1.0]; 
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; 
[UIView setAnimationRepeatCount: 100]; 

CGPoint contentOffset = scrollView.contentOffset; 
contentOffset.y += 50; 
scrollView.contentOffset = contentOffset; 

scrollView.transform = CGAffineTransformIdentity; 
[UIView commitAnimations]; 

有什么想法吗？

Answer 1

你为什么试图手动滚动视图？你不能用方法

- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated 

？

无论如何，我相信你的动画不能如你所期望的那样工作的原因是因为你设置了重复次数而不是每次都重新渲染动画。如果要解决此问题，可以通过创建一个包装动画并通过上下文指针传递参数的方法，再次在动画回调中进行动画制作。

- (void) animateContentOffsetByAmount:(CGFloat)amount numberRemaining:(int)num { 
    if (num == 0) return; 

    [UIView setAnimationDelegate:self]; 
    [UIView setAnimationDidStopSelector: 
     @selector(scrollAnimationStoppedWithID:finished:context:)]; 

    //NSArray released in callback 
    NSArray* contextArray = [NSArray arrayWithObjects: 
     [NSNumber numberWithFloat:amount], 
     [NSNumber numberwithInt:num], nil] 
    [UIView beginAnimations:nil context:contextArray]; 
    [UIView setAnimationBeginsFromCurrentState: YES]; 
    [UIView setAnimationDuration:1.0]; 
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; 

    CGPoint contentOffset = scrollView.contentOffset; 
    contentOffset.y += amount; 
    scrollView.contentOffset = contentOffset; 

    scrollView.transform = CGAffineTransformIdentity; 
    [UIView commitAnimations]; 
} 

- (void) scrollAnimationStoppedWithID:(NSString*)id 
     finished:(NSNumber*)finished context:(void*)context { 
    NSArray* contextArray = (NSArray*)context; 
    CGFloat amount = [(NSNumber*)[contextArray objectAtIndex:0] floatValue]; 
    int count = [(NSNumber*)[contextArray objectAtIndex:1] intValue]; 
    count = count - 1; 
    [contextArray release]; 
    [self animateContentOffsetByAmount:amount numberRemaining:count] 
} 

然后在你的代码，只需调用

[self animateContentOffsetByAmount:50 numberRemaining:100];