如何創建多階段UIImageView動畫？

Question

我試圖做一個多級動畫，以便UIImageView（1）淡入，（2）移動，（3）滑出屏幕。

只有階段1似乎工作。我究竟做錯了什麼？下面的代碼：

// 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

您需要添加一個調用自己設置爲動畫委託：

[UIView setAnimationDelegate:self]; 

這將取消設置自己爲委託（設置爲無）是個好主意最後一個動畫塊。

Answer 2

你的問題的完整的解決方案是：

1）設置動畫代表

2）使用正確的選擇和方法簽名

[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 
}