如何使用scrollRectToVisible滚动到图像的中心？

Question

我有一个带有缩放和平移功能的 UIScrollView 。我希望图像在用户命令后滚动到中心。我的问题是计算图像中心的框架的大小和位置。

有谁知道如何计算图像中心的正确框架？问题是，如果 ZoomScale 不同，框架会发生变化。

谢谢！

Answer 1

如果有人需要的话，这里可能有更好的代码；-)

UIScrollView+CenteredScroll.h：

@interface UIScrollView (CenteredScroll)

-(void)scrollRectToVisibleCenteredOn:(CGRect)visibleRect
                            animated:(BOOL)animated;

@end

UIScrollView+CenteredScroll.m：

@implementation UIScrollView (CenteredScroll)

-(void)scrollRectToVisibleCenteredOn:(CGRect)visibleRect
                            animated:(BOOL)animated
{
  CGRect centeredRect = CGRectMake(visibleRect.origin.x + visibleRect.size.width/2.0 - self.frame.size.width/2.0,
                                   visibleRect.origin.y + visibleRect.size.height/2.0 - self.frame.size.height/2.0,
                                   self.frame.size.width,
                                   self.frame.size.height);
  [self scrollRectToVisible:centeredRect
                   animated:animated];
}

@end

Answer 2

根据 Daniel Bauke 的回答，我更新了他的代码以包括缩放比例：

@implementation UIScrollView (jsCenteredScroll)

-(void)jsScrollRectToVisibleCenteredOn:(CGRect)visibleRect
                            animated:(BOOL)animated
{

    CGPoint center = visibleRect.origin;
    center.x += visibleRect.size.width/2;
    center.y += visibleRect.size.height/2;

    center.x *= self.zoomScale;
    center.y *= self.zoomScale;


    CGRect centeredRect = CGRectMake(center.x - self.frame.size.width/2.0,
                                     center.y - self.frame.size.height/2.0,
                                     self.frame.size.width,
                                     self.frame.size.height);
    [self scrollRectToVisible:centeredRect
                     animated:animated];
}

@end

Answer 3

private func centerScrollContent() {
    let x = (imageView.image!.size.width * scrollView.zoomScale / 2) - ((scrollView.bounds.width) / 2)
    let y = (imageView.image!.size.height * scrollView.zoomScale / 2) - ((scrollView.bounds.height) / 2)
    scrollView.contentOffset = CGPointMake(x, y)
}

Answer 4

好的，已经开始工作了。这是代码，以防有人需要：

CGFloat tempy = imageView.frame.size.height;
CGFloat tempx = imageView.frame.size.width;
CGRect zoomRect = CGRectMake((tempx/2)-160, (tempy/2)-240, myScrollView.frame.size.width, myScrollView.frame.size.height);
[myScrollView scrollRectToVisible:zoomRect animated:YES];