制作平滑的动画入口，退出和交换两个图像视图

Question

我正在使用UIView的动画功能将一条鱼的图像游到屏幕上，当屏幕中间已经存在一条鱼时，将它游走并游过一条新鱼。鱼的选择是从单独的tableview控制器发送的。

为了实现这一点，我保留了UIImageView的两个实例变量，并在动画完成后为self.fishViewNext交换self.fishViewCurrent（参见下面的代码）。

我的问题是当用户在下一条鱼有机会到达之前快速按下新的表格单元格时。我的快速解决方案是延迟添加鱼的新消息，此刻什么都不做。这适用于2个快速触摸，但不是更多。我正在寻找想法，如果有人知道如何改进下面的代码，以便动画是平滑的，你可以点击任何最终显示的图像是最后一次点击。这里重要的方法是：

创建第一个图像视图：

- (void) createFish {

self.fishViewCurrent = [[[UIImageView alloc] init] autorelease];
self.fishViewCurrent.contentMode = UIViewContentModeScaleAspectFit;
self.fishViewCurrent.bounds = CGRectMake(0.0f, 0.0f, kFishWidth, kFishHeight);
self.fishViewCurrent.center = CGPointMake(-kFishWidth, kFishYPos); // off the screen to the left
[self addSubview:self.fishViewCurrent];

}

选择tableview单元格时调用的公共方法：

- (void) addFish:(UIImage *)fish {

if (self.fishViewNext) {
    [self performSelector:@selector(addFish:) withObject:(UIImage *)fish afterDelay:1.0];
    return;
}
self.fishViewNext = [[[UIImageView alloc] initWithImage:fish] autorelease];
self.fishViewNext.contentMode = UIViewContentModeScaleAspectFit;
self.fishViewNext.bounds = CGRectMake(0.0f, 0.0f, kFishWidth, kFishHeight);
self.fishViewNext.center = CGPointMake(self.bounds.size.width + kFishWidth, kFishYPos);  // off the screen right
[self addSubview:self.fishViewNext];

[UIView beginAnimations:@"swimFish" context:nil];
[UIView setAnimationDuration:2.0f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationBeginsFromCurrentState:YES]; 
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(fishSwamOffHandler:finished:context:)];
[UIView setAnimationRepeatAutoreverses:NO];

self.fishViewNext.center = CGPointMake(self.center.x, kFishYPos); // center
self.fishViewCurrent.center = CGPointMake(-kFishWidth, kFishYPos);  // exit stage left

[UIView commitAnimations];   
}

处理程序将'下一个'鱼（UIImageView）切换为'当前'：

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

[self.fishViewCurrent removeFromSuperview]; 
self.fishViewCurrent = self.fishViewNext;
self.fishViewNext = nil;
}

Answer 1

最简单的事情是创建一个ivar BOOL，比如说_fishIsSwimming，然后_queuedFishView然后改变addFish的开头：看起来像这样：

- (void) addFish:(UIImage *)fish 
{
    // queue the most recent fish, if one was passed in
    if(fish)    
        self.queuedFishView = [[[UIImageView alloc] initWithImage:fish] autorelease];

    // If something is swimming, leave now
    if(_fishIsSwimming)
        return;

    // If we get here and there's no queued fish, leave now
    if(!self.queuedFishView)
        return;

    // We have a queued fish and nothing is swimming, so do the queued fish next 
    // and clear the queued fish
    _fishIsSwimming = YES;
    self.nextFishView = self.queuedFishView;
    self.queuedFishView = nil;
    // Then carry on as normal
}

然后在动画完成回调中，执行以下操作：

-(void) fishSwamOffHandler:(NSString*)animationID finished:(NSNumber*)finished context:(void*)context 
{
    // We're done animating, so ready to do another swimming fish
    _fishIsSwimming = NO;

    [self.fishViewCurrent removeFromSuperview]; 
    self.fishViewCurrent = self.fishViewNext;
    self.fishViewNext = nil;

    // now call to add another fish with nil, so that it will use 
    // the queued fish if there is one and otherwise just early out
    [self addFish:nil];    
}    

所以会发生的事情是你总是在queuedFishView中维护最近传入的鱼，然后一旦动画结束，你就可以回到addFish，如果还有一条鱼等着你就发送它。如果不是，您只需等待按下按钮发送的下一个