Objective-C：块中的动画

Question

我有一个 UIImageView sliderPump，我通过一个接一个地调用两个方法从屏幕的右侧移动到左侧无限次：

    -(void)pumpGoesRight
    {
        if (slide)
        {
            [UIView animateWithDuration:0.8 animations:^
             {

                 [sliderPump setFrame:CGRectMake(sliderPump.frame.origin.x+235, sliderPump.frame.origin.y, sliderPump.frame.size.width, sliderPump.frame.size.height)];

             } completion:^(BOOL finished)
             {
                 [self pumpGoesLeft];
             }];
        }
        else
            return;
    }
    -(void)pumpGoesLeft
    {
        if (slide)
        {

            [UIView animateWithDuration:0.8 animations:^
             {
                 [sliderPump setFrame:CGRectMake(sliderPump.frame.origin.x-235, sliderPump.frame.origin.y, sliderPump.frame.size.width, sliderPump.frame.size.height)];

             } completion:^(BOOL finished)
             {
                 [self pumpGoesRight];
             }];

            [self performSelector:@selector(pumpGoesRight) withObject:nil afterDelay:0.8];
        }
        else
            return;

}

然后我使用这段代码找出 UIImageView X 的位置 sliderPump 并停止动画：

-(void)stop
{
    slide = NO;
    NSLog(@"Slide Pump position: %f", sliderPump.layer.frame.origin.x);
    [self.view.layer removeAllAnimations];   
}

问题是当我调用 stop 方法时，我想得到 sliderPump 的当前位置，但我得到的是 sliderPimp 在结束时的最终位置动画，即使动画尚未完成。我怎样才能得到框架的当前位置？谢谢！

Answer 1

你应该使用表现层。

NSLog(@"Slide Pump position: %f", [sliderPump.layer.presentationLayer frame].origin.x);

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