缩放 - 弹跳时,UIScrollView的zoomScale属性不会更新

Question

现在我有一个超出UIScrollView的视图.由于许多原因,它不能简单地在scrollview中.所以我现在正在做的是,当UIScrollView被缩放/平移时,我更新了我的其他辅助视图.我遇到的唯一问题是,当视图重新回到最小或最大比例时,不会调整zoomScale值.有关如何在动画效果时获取此值的任何建议吗？

示例代码:

self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, appSize.width, appSize.height)];
self.scrollView.contentSize = CGSizeMake(appSize.width * 2, appSize.height * 2);

self.scrollView.indicatorStyle = UIScrollViewIndicatorStyleWhite;
self.scrollView.delegate = self;
self.scrollView.bounces = YES;
self.scrollView.bouncesZoom = YES;
self.scrollView.alwaysBounceHorizontal = YES;
self.scrollView.alwaysBounceVertical = YES;
self.scrollView.showsHorizontalScrollIndicator = YES;
self.scrollView.showsVerticalScrollIndicator = YES;

self.scrollViewZoomView = [[UIView alloc] initWithFrame:CGRectMake(0, 0,
                                                                   appSize.width * 2,
                                                                   appSize.height * 2)];
[[self scrollView] addSubview:self.scrollViewZoomView];

float minZoomScale = 2.0f;

self.scrollView.minimumZoomScale = minZoomScale;
self.scrollView.maximumZoomScale = 1.0f;
self.scrollView.zoomScale = self.scrollView.minimumZoomScale;

然后是自我

-(void) scrollViewDidZoom:(UIScrollView *)scrollView {
    float scale = [scrollView zoomScale];
    [self updateAuxViewScale:scale];
}

Answer 1

缩放的反弹是动画,因此zoomScale即使动画仍在运行,属性也会立即成为动画的目标值.如果您想将滚动视图所具有的缩放比例应用于另一个视图,则可以使用以下方法检索它:

1. 在-scrollViewDidScroll:检查内容是否视图具有动画.
2. 如果没有动画,则仅设置新的缩放比例.
3. 如果有动画,请获取其中一个的持续时间(持续时间应全部相等),并将具有该持续时间的视图设置为新的缩放比例.

这种方法并不优雅,但它确实有效.以下是一些可以帮助您入门的代码:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat zoomScale = _scrollView.zoomScale;

    CALayer *layer = _contentView.layer;
    NSArray *animationKeys = [layer animationKeys];

    if (animationKeys.count == 0) {
        // set zoomScale on target view
    } else {
        CFTimeInterval duration = 0.0;
        for (NSString *animationKey in animationKeys) {
            CAAnimation *animation = [layer animationForKey:animationKey];
            duration = animation.duration;
            break;
        }
        // easeInEaseOut is the default animation when the zoom bounces
        [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
            // set zoomScale on target view
        } completion:nil];
    }
}

Answer 2

由于这个答案,很明显可以使用它presentationLayer来获得正确的值.我创建了一个UIScrollView category为其添加特殊的getter zoomScale,contentOffset并且contentSize即使UIScrollView是动画也会返回正确的值.

你可以在这里找到回购:https://github.com/bddckr/BDDRScrollViewExtensions