如何更改 UICollection UIImageView 中的 UIimage？

Question

我有一个 UICollectionView，其中包含一个 UIImageView，并且只有一行。我试图在点击时将图像更改为选定图像，但由于某种原因图像不会更新。当 UICollectionView 调用时设置 UIImage：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

但调用时不会更新：

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

这是代码，如您所见，我已经尝试过 setNeedsDisplay、reloadData、setImage 并使 UImageView 本身无效，而不是在 cellForItemAtIndexPath 中设置它...None 它已经起作用。

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

    UICollectionViewCell *cell;
    UIImage *curImage;

    static NSString *cellAvatarMediaIdentifier = @"cvAvatarCell";


    cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellAvatarMediaIdentifier forIndexPath:indexPath];

    Child *currentChild = [self.children objectAtIndex:indexPath.row];

    curImage = [UIImage imageNamed:@"male.png"];

    UIImageView *childSilhouetteView = (UIImageView *)[cell viewWithTag:300];

    if (curImage != nil)
    {
        // this WORKS !!!!
        [childSilhouetteView setImage:curImage];
    }

    return cell;
}

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

        Child *currentChild = [self.children objectAtIndex:indexPath.row];

        UIImageView *childSilhouetteView = (UIImageView *)[collectionView viewWithTag:300];

        selectedImage = [UIImage imageNamed:@"male_selected.png"];

        if (selectedImage != nil)
        {
                // This does NOT work, image is never updated
                NSLog(@"Before setting image");
                childSilhouetteView = nil;

                [childSilhouetteView setImage:selectedImage];
                [childSilhouetteView setNeedsDisplay];
                [collectionView reloadData];
        }
}

Answer 1

您还需要在didSelectItemAtIndexPath:中找到对应的child，目前您正在使用标签访问collectionView的视图。

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

        Child *currentChild = [self.children objectAtIndex:indexPath.row];

        UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];

        UIImageView *childSilhouetteView = (UIImageView *)[cell viewWithTag:300];

        selectedImage = [UIImage imageNamed:@"male_selected.png"];

        if (selectedImage != nil)
        {
                // This does NOT work, image is never updated
                NSLog(@"Before setting image");
              //  childSilhouetteView = nil;

                [childSilhouetteView setImage:selectedImage];
                [childSilhouetteView setNeedsDisplay];
               // [collectionView reloadData];
        }
}

如果您调用 reloadData，您的 collectionView 将被重绘，因此您将在视图中看到默认图像。

Answer 2

首先要访问特定单元格的项目，首先需要获取单元格。

检查这个答案： UICollectionView didSelectRowAtIndexPath doesn't work

其次确保编译器进入您正在检查图像是否为 nil 的状态。确保 "male_selected.png" 存在于同名的资产文件夹中。

第三步是删除所有不必要的代码。那你可以走了

如何更改 UICollection UIImageView 中的 UIimage？

How to change UImage in UICollection UIImageView?

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