iphone - 如何创建多阶段 UIImageView 动画？

Question

我正在尝试制作多阶段动画，以便 UIImageView (1) 淡入，(2) 移动，(3) 滑出屏幕。

似乎只有第 1 阶段有效。我究竟做错了什么？这是代码：

// FIRST PART - FADE IN
-(void)firstAnim
{
    // 'sprite' is a UIImageView
    [sprite setAlpha:0.1f];
    [UIView beginAnimations:@"anim1" context:NULL];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:0.25];
    [UIView setAnimationDidStopSelector:@selector(secondAnim)];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];
    [sprite setAlpha:1.0f];
    [UIView commitAnimations];
}


// SECOND PART - MOVE
-(void)secondAnim
{
    [UIView beginAnimations:@"anim2" context:NULL];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:0.5];
    [UIView setAnimationDidStopSelector:@selector(thirdAnim)];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];
    sprite.frame = CGRectMake(170, 184, 20, 20);
    [UIView commitAnimations];
}

// THIRD PART - SLIDE OFF SCREEN
-(void)thirdAnim
{   
    [UIView beginAnimations:@"anim3" context:NULL];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:0.5];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    sprite.frame = CGRectMake(170, 420, 20, 20);
    [UIView commitAnimations];
}

Answer 1

您需要添加一个调用以将自己设置为动画委托：

[UIView setAnimationDelegate:self];

在最后一个动画块中将自己取消设置为代理（设置为 nil）是一个好主意。

Answer 2

您的问题的完整解决方案是：

1）设置动画委托

2）使用正确的选择器和方法签名

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:.5];
[UIView setAnimationDelegate:self];  //set delegate!
[UIView setAnimationDidStopSelector:
    @selector(secondAnim:finished:context:)];


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

    //animation #2
}