如何更改UICollection UIImageView中的UImage？(How to change UImage in UICollection UIImageView?)

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

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

但它在调用时不会更新：

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

这里是代码，你可以看到我已经尝试过setNeedsDisplay，reloadData，setImage并取消UImageView本身，而不是在cellForItemAtIndexPath中设置它...没有任何工作。

- (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]; } }

I have a UICollectionView which contains a UIImageView and is only one row. I am trying to change the image to a selected image when tapped but the image will not update for some reason. The UIImage is set when the UICollectionView calls:

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

but it will not update when it calls:

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

Here is the code, as you can see I already tried setNeedsDisplay , reloadData, setImage and nullifying the UImageView itself, not setting it in the cellForItemAtIndexPath ... None of it has worked.

- (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]; } }

最满意答案

您还需要在didSelectItemAtIndexPath:找到相应的子项didSelectItemAtIndexPath: ，当前您正在使用标记访问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]; } }

如果你调用reloadData ，你的collectionView将被重画，所以你会在你的视图中看到默认的图像。

You also need to find the corresponding child in didSelectItemAtIndexPath:, currently you're accessing the collectionView's view with tag.

- (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]; } }

If you call reloadData, your collectionView will be redrawn so you will see the default images on your views.

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