iOS:ScrollView无限分页-重复的端盖 [英] iOS: ScrollView infinite paging - Duplicate end caps

问题描述

我对ScrollView中的无限分页有疑问.在我的应用程序中，ScrollView中只有3个子视图.每个子视图都是从xib文件加载的.通常，它看起来像ScrollView中的ABC.我想进行无限分页，所以我添加了端盖，现在看起来像CABCA.如果用户在第一个C上，则跳转到常规C；如果用户在最后一个A上，则跳转到常规A.这是代码:

I have a question about infinite paging in a ScrollView. In my app I have only 3 subviews in ScrollView. Each subview is loaded from xib file. Normally it looks like ABC in ScrollView. I wanted to make infinite paging so I added end caps and now it looks like CABCA. If the user is on the first C, it jumps to regular C and if user is on the last A, it jumps to regular A. Here is a code:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)sender {

  if (scrollView.contentOffset.x == 0)
  {
      [scrollView scrollRectToVisible:CGRectMake
      ((scrollView.frame.size.width * 3), 0,
      scrollView.frame.size.width,
      scrollView.frame.size.height) animated:NO];
  } 
  else if (scrollView.contentOffset.x == scrollView.frame.size.width * 4)
  {
     [scrollView scrollRectToVisible:CGRectMake
     (scrollView.frame.size.width, 0,
      scrollView.frame.size.width,
      scrollView.frame.size.height) animated:NO];
   }
}

它现在可以完美运行了.但是我为每个子视图都有ViewController，这就是我将它们添加到ScrollView的方式:

It works perfectly now. But I have ViewController for each subview and this is how I am adding them to ScrollView:

  subViewController1 = [[SubViewController1 alloc] initWithNibName:@"SubView" bundle:nil];
  subViewController1.view.frame =
    CGRectMake(0, 0, scrollView.frame.size.width, scrollView.frame.size.height);
  [scrollView addSubview:subViewController1.view];

问题是A和C视图有一个副本，所以现在我有5个控制器，而不是3个.如果要在A视图中添加某些内容，我也必须将其添加到A视图的副本中.

Problem is that there is one duplicate of A and C view so now I have 5 controllers instead of 3. And If I want to add something into a A view, I have to add it also into duplicate of A view.

有没有一种方法可以使用一个控制器控制视图A和A的副本，因此我不必创建一个控制器的两个实例?谢谢.

Is there a way how to control view A and duplicate of A with one controller so I don't have to create two instances of one controller? Thank you.

推荐答案

更好的是，您不需要具有重复的视图A和视图C，只需在操作contentOffset的同时将它们在- (void)scrollViewDidScroll:(UIScrollView *)scrollView中移动即可.

Better still, you don't need to have duplicate view A's and duplicate view C's, you just move them around in - (void)scrollViewDidScroll:(UIScrollView *)scrollView while manipulating the contentOffset.

设置:可能与您已经完成的操作非常相似.

Setup: probably very similar to how you already do it.

将UIScrollView设置为contentSize是其边界宽度的3倍.确保分页功能已打开并关闭.

Set your UIScrollView to have contentSize 3 times it's bounds width. Make sure paging is turned on and bouncing off.

从左到右将ABC子视图添加到UIScrollView.

Add your ABC subviews to the UIScrollView from left to right.

您的ViewController中还有一个名为_contentViews的数组 包含您的UIViews ABC.

Also have an array in your ViewController called _contentViews that contains your UIViews ABC.

然后实现此功能，它将重置内容偏移并在滚动视图到达边缘时同时移动子视图:

Then implement this which will reset the content offset and move your subviews around at the same time when the scrollview reaches the edges:

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {

    if(scrollView.contentOffset.x == 0) {
        CGPoint newOffset = CGPointMake(scrollView.bounds.size.width+scrollView.contentOffset.x, scrollView.contentOffset.y);
        [scrollView setContentOffset:newOffset];
        [self rotateViewsRight];
    }
    else if(scrollView.contentOffset.x == scrollView.bounds.size.width*2) {
        CGPoint newOffset = CGPointMake(scrollView.contentOffset.x-scrollView.bounds.size.width, scrollView.contentOffset.y);
        [scrollView setContentOffset:newOffset];
        [self rotateViewsLeft];
    }
}

-(void)rotateViewsRight {
    UIView *endView = [_contentViews lastObject];
    [_contentViews removeLastObject];
    [_contentViews insertObject:endView atIndex:0];
    [self setContentViewFrames];

}

-(void)rotateViewsLeft {
    UIView *endView = _contentViews[0];
    [_contentViews removeObjectAtIndex:0];
    [_contentViews addObject:endView];
    [self setContentViewFrames];

}

-(void) setContentViewFrames {
    for(int i = 0; i < 3; i++) {
        UIView * view = _contentViews[i];
        [view setFrame:CGRectMake(self.view.bounds.size.width*i, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
    }
}

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