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【Swift 4.0】iOS 11 UICollectionView 长按拖拽删除崩溃的问题

日期：2017-12-03点击：755收藏

功能

用 UICollectionView 实现两个 cell 之间的位置交互或者拖拽某个位置删除

问题

iOS 11 以上拖拽删除会崩溃，在 iOS 9、10 都没有问题

错误

017-10-11 11:38:02.692004+0800 MOCR[2585:1047221] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempting to invalidate an item at an invalid indexPath: <NSIndexPath: 0x1c442a680> {length = 2, path = 0 - 1} globalIndex: 1 numItems: 1'
*** First throw call stack:
(0x181f3bd38 0x181450528 0x181f3bc0c 0x1828cac24 0x18be1091c 0x18bdd2ab8 0x18b4b74ac 0x18b4b48b8 0x18b569a4c 0x18bdd9e98 0x10275d49c 0x10275d45c 0x102762050 0x181ee3f20 0x181ee1afc 0x181e022d8 0x183c93f84 0x18b3af880 0x1009a753c 0x18192656c)
libc++abi.dylib: terminating with uncaught exception of type NSException

代码

    func  handleLongGesture ( gesture :  UILongPressGestureRecognizer ) { 
   
      switch ( gesture . state ) { 
   
      case  . began : 
          guard  let  selectedIndexPath  =  self . collectionView . indexPathForItem ( at :  gesture . location ( in :  self . collectionView ))  else  { 
              break 
          } 
          collectionView . beginInteractiveMovementForItem ( at :  selectedIndexPath ) 
      case  . changed : 
          collectionView . updateInteractiveMovementTargetPosition ( gesture . location ( in :  gesture . view !)) 
      case  . ended : 
          self . collectionView . endInteractiveMovement () 
          // 检测是否删除操作，是的话删除数据并调用 reloadData() 
      default : 
          collectionView . cancelInteractiveMovement () 
      } 
 } 
 
  

分析

测试发现调用 beginInteractiveMovementForItem 和 endInteractiveMovement 也会触发 reloadData 操作，这样删除前后会调用两次 reloadData，但是 reloadData 又是异步操作，所以就报错了。

解决

     func  handleLongGesture ( gesture :  UILongPressGestureRecognizer ) { 
   
      switch ( gesture . state ) { 
   
      case  . began : 
          guard  let  selectedIndexPath  =  self . collectionView . indexPathForItem ( at :  gesture . location ( in :  self . collectionView ))  else  { 
              break 
          } 
          collectionView . beginInteractiveMovementForItem ( at :  selectedIndexPath ) 
      case  . changed : 
          collectionView . updateInteractiveMovementTargetPosition ( gesture . location ( in :  gesture . view !)) 
      case  . ended : 
          self . collectionView . endInteractiveMovement () 
          DispatchQueue . main . asyncAfter ( deadline : . now () + . milliseconds ( 300 ),  execute : { [ weak  self ]  in 
              // 检测是否删除操作，是的话删除数据并调用 reloadData() 
          }) 
      default : 
          collectionView . cancelInteractiveMovement () 
      } 
 } 
 
  