Ios 点击UICollectionView从单元格中获取图像

因此，我想要实现的是，当用户点击UICollectionView中的单元格时，该单元格中的图像将显示在下一个UIView中

为了实现这一点，我使用了委托方法

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

和NSUserDefaults。我就是这样做的

打开手机

从#1的单元格的UIImageView获取图像

将图像转换为NSData

将数据放入NSUserDefaults

执行到下一个视图控制器的切换

从NSUserDefault获取数据

转换为UIImage并显示在UIImageView中

代码如下：

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    NewsfeedCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    NSData *data = [[NSData alloc]initWithData:UIImagePNGRepresentation(cell.ItemImageView.image)];
    NSLog(@"Before Data %@", data);
    NSUserDefaults *def = [NSUserDefaults standardUserDefaults];
    [def setObject:data forKey:@"feedData"];
    [def synchronize];
    [self performSegueWithIdentifier:@"itemTappedSegue" sender:self];  
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSUserDefaults *def = [NSUserDefaults standardUserDefaults];
    NSData *data = [def objectForKey:@"feedData"];
    NSLog(@"After Data:%@", data);
    UIImage *image = [[UIImage alloc]initWithData:data];
    self.imageView.image = image;
}

应该工作，但不是。我得到随机结果。有时在下一个UIView中没有图像，有时有图像但不是我点击的图像

编辑：：以下是

cellForItemAtIndexpath

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *CellIdentifier = @"Cell";
NewsfeedCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
if(response2.count > 0){
    cell.usernameLabel.text = [self getUsername:[response2 objectAtIndex:indexPath.item]];
    [UIApplication sharedApplication].networkActivityIndicatorVisible =YES;
    dispatch_queue_t getUserAvatar = dispatch_queue_create("Avatar downloader", NULL);
    dispatch_queue_t getFeed = dispatch_queue_create("Feed downloader", NULL);
    dispatch_async(getUserAvatar, ^{
        NSString *urlString = [self getAvatarUrl:[response2 objectAtIndex:indexPath.item]];
        NSURL *url = [[NSURL alloc]initWithString:urlString];
        NSData *avatarData = [NSData dataWithContentsOfURL:url];
        dispatch_async(dispatch_get_main_queue(), ^{
            cell.DPImageView.layer.masksToBounds = YES;
            cell.DPImageView.layer.cornerRadius = 6.0f;
            cell.DPImageView.image = [UIImage imageWithData:avatarData];
        });
    });
    dispatch_async(getFeed, ^{
        NSString *URLString = [self getFeedUrl:[response2 objectAtIndex:indexPath.item]];
        NSURL *URL = [[NSURL alloc]initWithString:URLString];
        NSData *feedData = [NSData dataWithContentsOfURL:URL];
        dispatch_async(dispatch_get_main_queue(), ^{
            cell.ItemImageView.image = [UIImage imageWithData:feedData];
            cell.ItemImageView.layer.masksToBounds = YES;
            cell.LikeBtn.hidden = NO;
            cell.CommentBtn.hidden = NO;
            cell.usernameLabel.hidden = NO;
            cell.DPImageView.hidden = NO;
        });
    });
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
else{
    //cell.ItemImageView.image = [UIImage imageNamed:@"NoFeed.png"];
    cell.LikeBtn.hidden = YES;
    cell.CommentBtn.hidden = YES;
    cell.usernameLabel.hidden = YES;
    cell.DPImageView.hidden = YES;
}
return cell;

你为什么这样做：

    NewsfeedCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

?？ 您需要获取indexPath的单元格，而不是从池中创建单元格。 使用：

---

相反。

在

didSelectItemAtIndexPath:

方法中更改行

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    NewsfeedCell *cell = [collectionView cellForItemAtIndexPath:indexPath]; // put this line in place of creating cell

    NSData *data = [[NSData alloc]initWithData:UIImagePNGRepresentation(cell.ItemImageView.image)];
    NSLog(@"Before Data %@", data);
    NSUserDefaults *def = [NSUserDefaults standardUserDefaults];
    [def setObject:data forKey:@"feedData"];
    [def synchronize];
    [self performSegueWithIdentifier:@"itemTappedSegue" sender:self];  
}

---

也许您已经解决了这个问题，但我遇到了一个类似的问题，并发现

UICollectionView

从0开始

例如，我的图像被命名为image_1、image_2等等。但是如果我从图像_1开始，第一个单元格中没有任何内容，因此必须从图像_0、图像_1开始，以此类推

---

希望这对任何人都有帮助。

我现在正在做这件事。上一次点击的图像。如果我第一次点击图像（图像A），我在下一个视图中什么也看不到。我返回，然后点击另一个图像（图像B）我从上一个点击中获得图像A您可以显示cellForItemAtIndexPath:Method的实现吗很抱歉响应太晚，但我已经添加了实现

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    NewsfeedCell *cell = [collectionView cellForItemAtIndexPath:indexPath]; // put this line in place of creating cell

    NSData *data = [[NSData alloc]initWithData:UIImagePNGRepresentation(cell.ItemImageView.image)];
    NSLog(@"Before Data %@", data);
    NSUserDefaults *def = [NSUserDefaults standardUserDefaults];
    [def setObject:data forKey:@"feedData"];
    [def synchronize];
    [self performSegueWithIdentifier:@"itemTappedSegue" sender:self];  
}