Question

我尝试了非常简单的事情：在按下按钮的UICollectionViewCell's imageView上添加图像。（实际上，CollectionViewCell - 是UIImageView IBOutlet）

的自定义单元格

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
    self.cell=cell;
    return cell;
}

- (IBAction)actionAddImage:(UIBarButtonItem *)sender {
    UIImage* image=[UIImage imageNamed:@"1.jpg"];
   self.cell.imageView.image=image;
   NSIndexPath* path= [self.collectionView indexPathForCell:self.cell];
   [self.collectionView reloadItemsAtIndexPaths:@[path]];
}

只有一个细胞。在第一个按钮按下没有任何反应，在第二个 - 图像出现。我把NSLog，并透露，

CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

返回新单元格而不是现有单元格。虽然indexPath强烈（section = 0，row = 0），即。只有一个细胞。但是，reloadData完美无缺，但当然没有动画。

- (IBAction)actionAddImage:(UIBarButtonItem *)sender {
    UIImage* image=[UIImage imageNamed:@"1.jpg"];
   self.cell.imageView.image=image;
   [self.collectionView reloadData];
}

Answer 1

_array =[NSMutableArray arrayWithObjects:@{@"option":[NSNumber numberWithBool:NO]},@{@"option":[NSNumber numberWithBool:NO]},@{@"option":[NSNumber numberWithBool:NO]},@{@"option":[NSNumber numberWithBool:NO]}, nil];

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    questionImageCollectionViewCell * cell=[self.questionCollectionView dequeueReusableCellWithReuseIdentifier:@"coustomCell" forIndexPath:indexPath];
    cell.optionImageView.image=[UIImage imageNamed:[_optionImageArr objectAtIndex:indexPath.item]];


    NSDictionary *dic = self.array[indexPath.row];

    if ([dic[@"option"] boolValue]) {
        [cell.rightTickImg setHidden:NO];
    }else{
      [cell.rightTickImg setHidden:YES];

    }
   // [cell.rightTickImg setHidden:YES];
    return cell;


}


- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{

        //[self.array removeObjectAtIndex:indexPath.row];
    NSDictionary *dic = @{@"option":[NSNumber numberWithBool:YES]};
    [self.array insertObject:dic atIndex:indexPath.row];

    [collectionView reloadItemsAtIndexPaths:@[indexPath]];

}

Answer 2

第一次，您的代码非常不安全。在“collectionView：cellForItemAtIndexPath：”中“创建”时，不应该分配可重用的单元格，而不是尝试这样做：

- (IBAction)actionAddImage:(UIBarButtonItem *)sender 
{
    NSIndexPath *path    = [NSIndexPath indexPathForItem:0 inSection:0]; // i suppose you can reload cell at section 0 position 0
    CollectionViewCell *cell = (CollectionViewCell *)[_collectionView cellForItemAtIndexPath:path];
    UIImage *image = [UIImage imageNamed:@"1.jpg"];

    cell.imageView.image = image;

    .... reload _collectionView at Path 'path' ....
}

在其他事情之间，您对可重用单元格所做的外部引用并非在时间上不可变。

UICollectionView reloadData有效，但reloadItemsAtindexPaths不是

2 个答案: