如何创建多阶段 UIImageView 动画?

问题描述

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.

I'm trying to do a multistage animation, so that a UIImageView (1) fades in, (2) moves, (3) slide off the screen.

似乎只有第 1 阶段有效.我究竟做错了什么?代码如下:

Only stage 1 seems to work. What am I doing wrong? Here's the code:

// 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];
}

推荐答案

你需要添加一个调用来设置自己为动画代理:

You need to add a call to set yourself as the animation delegate:

[UIView setAnimationDelegate:self];

最好在最后一个动画块中将自己取消设置为代理(设置为 nil).

It would be a good idea to unset yourself as the delegate (set to nil) in the last animation block.

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