正文
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()
}
}
加一个延迟处理就行