在UICollectionView中在当前索引之前添加对象(Adding an object before the current index in UICollectionView)

 我有一个简单的集合视图，有两种类型的单元格。 计数器单元和“添加”单元。 我的目标是在添加新对象后将“添加”单元格保留在索引的末尾。 当我运行应用程序时，我的“添加”单元格出现，但是当按下“添加”按钮时出现错误。 
 
 这是错误： 
 
 
 
 由于未捕获的异常'NSInternalInconsistencyException'而终止应用程序，原因：'无效更新：第0节中的项目无效。更新后的现有部分中包含的项目数（1）必须等于该项目中包含的项目数更新前的部分（1），加上或减去从该部分插入或删除的项目数（插入1个，删除0个），加上或减去移入或移出该部分的项目数量（0移入，0移动）出）。” 
 
 
 这是我的代码： 
 
// retrievedCounters is an NSMutableDictionary

- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView {
   // only want one section
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section {
    // get the current count and add one for the "add" cell
    return retrievedCounters.count + 1;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell;

    // check whether the index path is at the very end and add the appropriate cell

    if (indexPath.row == retrievedCounters.count) {
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"AddCounter" forIndexPath:indexPath];
    }

    else {
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CounterCell" forIndexPath:indexPath];
    }

    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    [collectionView deselectItemAtIndexPath:indexPath animated:YES];

     // insert new counter at index path
     [self.collectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:retrievedCounters.count-1 inSection:0]]];

}
 
 谢谢任何可以提供帮助的人！ 

I have a simple collection view that has two types of cells. A counter cell, and an "add" cell. My goal is to have the "add" cell remain at the end of the index after new objects are added. When I run the application my "add" cell appears but I get an error when the "add" button is pressed.
 
Here is the error:
 
 
 
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of items in section 0. The number of items contained in an existing section after the update (1) must be equal to the number of items contained in that section before the update (1), plus or minus the number of items inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of items moved into or out of that section (0 moved in, 0 moved out).'
 
 
And here is my code:
 
// retrievedCounters is an NSMutableDictionary

- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView {
   // only want one section
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section {
    // get the current count and add one for the "add" cell
    return retrievedCounters.count + 1;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell;

    // check whether the index path is at the very end and add the appropriate cell

    if (indexPath.row == retrievedCounters.count) {
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"AddCounter" forIndexPath:indexPath];
    }

    else {
        cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"CounterCell" forIndexPath:indexPath];
    }

    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    [collectionView deselectItemAtIndexPath:indexPath animated:YES];

     // insert new counter at index path
     [self.collectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:retrievedCounters.count-1 inSection:0]]];

}
 
Thank you to anyone who can help!

原文：https://stackoverflow.com/questions/20412624