xcode UICollectionView reloadItemsAtIndexPaths
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UICollectionView reloadItemsAtIndexPaths
提问by Jdizzle Foshizzle
I've been trying to wrap my head around the reloadItemsAtIndexPaths method of UICollectionView.
我一直试图围绕 UICollectionView 的 reloadItemsAtIndexPaths 方法。
I have an array of objects called objectsArray. When a user scrolls to the bottom of my collection view, I fetch the next batch of objects from the backend and append it to objectsArray by calling [objectsArray addObjectsFromArray:objects]; After doing so, I call [self.collectionView reloadData] which I know is expensive.
我有一个名为objectsArray 的对象数组。当用户滚动到我的集合视图底部时，我从后端获取下一批对象并通过调用 [objectsArray addObjectsFromArray:objects] 将其附加到 objectsArray；这样做之后，我调用了 [self.collectionView reloadData]，我知道这很昂贵。
I'd like to optimize with the code below but I get an assertion failure when calling reloadItemsAtIndexPaths.
我想使用下面的代码进行优化，但在调用 reloadItemsAtIndexPaths 时出现断言失败。
if (self.searchPage == 0) {
parseObjectsArray = [[NSMutableArray alloc] initWithArray:relevantDeals];
[self.collectionView reloadData];
} else {
NSMutableArray *indexPaths = [[NSMutableArray alloc] init];
for (int i = 0; i < [relevantDeals count]; i++) {
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
[indexPaths addObject:indexPath];
}
[parseObjectsArray addObjectsFromArray:relevantDeals];
[self.collectionView reloadItemsAtIndexPaths:indexPaths];
//[self.collectionView reloadData];
}
Error: *Assertion failure in -[UICollectionView _endItemAnimations], /SourceCache/UIKit/UIKit-2903.2/UICollectionView.m:3716
错误： *-[UICollectionView _endItemAnimations] 中的断言失败，/SourceCache/UIKit/UIKit-2903.2/UICollectionView.m:3716
Any help/tips is greatly appreciated.
非常感谢任何帮助/提示。
Thanks!
谢谢！
回答by Dan Treiman
It looks like the items being added are new, in other words you are adding items which weren't there before. In that case, just replace reloadItemsAtIndexPaths:indexPaths with insertItemsAtIndexPaths:
看起来正在添加的项目是新的，换句话说，您正在添加以前不存在的项目。在这种情况下，只需将 reloadItemsAtIndexPaths:indexPaths 替换为 insertItemsAtIndexPaths：
[self.collectionView insertItemsAtIndexPaths:indexPaths]; // Use this for newly added rows
//[self.collectionView reloadItemsAtIndexPaths:indexPaths]; // Use this for existing rows which have changed
回答by Jdizzle Foshizzle
The assertion error was misleading. It wasn't until after I implemented
断言错误具有误导性。直到我实施之后
@try
{
[self.collectionView insertItemsAtIndexPaths:indexPaths];
}
@catch (NSException *except)
{
NSLog(@"DEBUG: failure to insertItemsAtIndexPaths. %@", except.description);
}
Did I realize was calculating my indexPaths wrong. My index offset for the new objects was off by one making my collectionview think I was adding more objects than I specified in numberOfItemsInSection.
我是否意识到计算我的 indexPaths 是错误的。我的新对象的索引偏移量减少了一个，使我的 collectionview 认为我添加的对象比我在 numberOfItemsInSection 中指定的要多。
Thanks for all those who attempted to help!
感谢所有试图提供帮助的人！
回答by Boris
This error often arises when you increase/decrease the number of items in the array but it doesn't match the data source method
当您增加/减少数组中的项目数但与数据源方法不匹配时，通常会出现此错误
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
Are you updating it appropriately?
你是否适当地更新它？
