Question

我有一个水平的收藏夹视图，用作4个屏幕/步骤的寻呼机。我禁用了水平滚动作为仅通过浮动按钮执行下一步操作的方式：

   let nextItem = self.selectedIndexPath.item + 1
   self.scrollToStep(index: IndexPath(item: nextItem, section: 0))


   func scrollToStep(index: IndexPath){
      selectedIndexPath = index
      collectionView.scrollToItem(at: index, at: .centeredHorizontally, animated: true)  
}

我第二次点击按钮，应用崩溃。

] *由于未捕获的异常而终止应用程序   'NSInvalidArgumentException'，原因：“试图滚动到无效   索引路径：{length = 2，路径= 0-4}'   * 第一个调用堆栈：（0 CoreFoundation 0x00000001088dd6fb __exceptionPreprocess + 331 1 libobjc.A.dylib
  0x0000000107e81ac5 objc_exception_throw + 48 2 CoreFoundation
  0x00000001088dd555 + [NSException提高：格式：] + 197 3 UIKitCore
  0x000000010b79ef93-[UICollectionView   _contentOffsetForScrollingToItemAtIndexPath：atScrollPosition：] + 212 4 UIKitCore 0x000000010b79f86b   -[UICollectionView _scrollToItemAtIndexPath：atScrollPosition：animated：] + 70 5 0x0000000105238770   $ s14 18ViewControllerC12scrollToStep5indexy10Foundation9IndexPathV_tF   + 480 6 0x00000001052358b5 $ s1 ar 010collectionF0_13cellForItemAtSo012UICollectionF4CellCSo0mF0C_10Foundation9IndexPathVtFySbcfU_   + 1701

Answer 1

4个屏幕/步骤由索引0-3表示。该错误明确指出了超出范围的错误。

您必须检查nextItem是否达到结束索引

let nextItem = self.selectedIndexPath.item + 1
if nextItem < 4 {
   self.scrollToStep(index: IndexPath(item: nextItem, section: 0))
}

Answer 2

var staticIndex = 0

在按钮单击操作中

if staticIndex < 3 {

                 var indexPath = IndexPath.init(row: staticIndex+1, section: 0)
          collectionView.scrollToItem(at: indexPath, at: .right, animated: true)
                    staticIndex += 1                        
      }

'尝试滚动到无效的索引路径：{length = 2，path = 0-4}

2 个答案: