使两个 UIScrollViews 跟随彼此滚动

问题描述

如何让两个滚动视图跟随彼此滚动?

How would I make two scroll views follow each others scrolling?

例如，我在屏幕左侧有一个滚动视图 (A)，其内容可以上下滚动，但不能左右滚动.滚动视图 B 匹配 A 的上下滚动，但也可以左右滚动.滚动视图 A 始终在屏幕上.

For instance, I have a scroll view (A) on the left of a screen, whose contents can scroll up and down, but not left and right. Scroll view B matches the up and down of A, but can also scroll left and right. Scroll view A is always on the screen.

-----------------------------------------------------------
|             |                                           |
|             |                                           |
|             |                                           |
|     A       |                    B                      |
|             |                                           |
|    scrolls  |                                           |
|   up & down |              scrolls all directions       |
|             |                                           |
-----------------------------------------------------------

我将如何做到这一点，以便(任一视图的)上下滚动也会使另一个视图沿相同的上下方向滚动?还是有其他方法可以做到这一点?

How would I make it so the the up and down scrolling (of either view) also makes the other view scroll in the same up-down direction? Or is there another method to do this?

推荐答案

将滚动视图 A 的委托设置为您的视图控制器...然后...

Set the delegate of scroll view A to be your view controller... then have...

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  CGPoint offset = scrollViewB.contentOffset;
  offset.y = scrollViewA.contentOffset.y;
  [scrollViewB setContentOffset:offset];
}

如果您希望双方互相关注，则为他们设置委托并使用...

If you want both to follow each other, then set delegate for both of them and use...

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  if([scrollView isEqual:scrollViewA]) {
    CGPoint offset = scrollViewB.contentOffset;
    offset.y = scrollViewA.contentOffset.y;
    [scrollViewB setContentOffset:offset];
  } else {
    CGPoint offset = scrollViewA.contentOffset;
    offset.y = scrollViewB.contentOffset.y;
    [scrollViewA setContentOffset:offset];
  }
}

上面可以重构为有一个方法，它接受两个滚动视图并匹配另一个.

The above can be refactored to have a method which takes in two scrollviews and matches one to the other.

- (void)matchScrollView:(UIScrollView *)first toScrollView:(UIScrollView *)second {
  CGPoint offset = first.contentOffset;
  offset.y = second.contentOffset.y;
  [first setContentOffset:offset];
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  if([scrollView isEqual:scrollViewA]) {
    [self matchScrollView:scrollViewB toScrollView:scrollViewA];  
  } else {
    [self matchScrollView:scrollViewA toScrollView:scrollViewB];  
  }
}

Swift 3 版本:

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if scrollView == scrollViewA {
            self.synchronizeScrollView(scrollViewB, toScrollView: scrollViewA)
        }
        else if scrollView == scrollViewB {
            self.synchronizeScrollView(scrollViewA, toScrollView: scrollViewB)
        }
    }

    func synchronizeScrollView(_ scrollViewToScroll: UIScrollView, toScrollView scrolledView: UIScrollView) {
        var offset = scrollViewToScroll.contentOffset
        offset.y = scrolledView.contentOffset.y

        scrollViewToScroll.setContentOffset(offset, animated: false)
    }

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