Ios 使用json加载UITableView图像未正确加载

我用它来通过JSON解析显示一些标签和图像到tableView，但是当滚动tableView图像时，图像在第一次启动时没有出现，我的意思是没有按顺序出现。请帮我解决这个问题

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
        self.customCellClass = [tableView dequeueReusableCellWithIdentifier:@"Cell"];
        if (self.customCellClass == nil)
        {
            self.customCellClass = [[CellCustom alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
        }
        self.customCellClass.nameLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"name"]; // label
        self.customCellClass.cityLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"region"]; // label

        NSString * stripped = [[[arrayData objectAtIndex:indexPath.row] objectForKey:@"summary"] stripHtml]; //label
        self.customCellClass.detailLabel.text = stripped;
        self.customCellClass.mainImage.image = nil;


        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
            NSData *data0 = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[[arrayData objectAtIndex:indexPath.row]objectForKey:@"images"]objectForKey:@"logo"]]];
            UIImage *image = [UIImage imageWithData:data0];

            dispatch_sync(dispatch_get_main_queue(), ^(void) {
                self.customCellClass.mainImage.image = image;
            });
        });
        return self.customCellClass;

}

---

替换

UITableView的
cellforrowatinexpath
方法中的以下代码：

//Check if cell has image or not
if(!self.customCellClass.mainImage.image)
{
   dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
   dispatch_async(q, ^{

      NSData *data0 = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[[arrayData objectAtIndex:indexPath.row]objectForKey:@"images"]objectForKey:@"logo"]]];
      UIImage *image = [UIImage imageWithData:data0];

      //Get main queue
      dispatch_async(dispatch_get_main_queue(), ^{

       /* This is the main thread again, where we set the tableView's image to be what we just fetched. */

       self.customCellClass.mainImage.image = image;

      });

   });
}

好的解决方案是，如果您正在使用，则使用
UIImageView+AFNetworking
category

NSURL *imageURL = [NSURL URLWithString:[[[arrayData objectAtIndex:indexPath.row]objectForKey:@"images"]objectForKey:@"logo"]]
[self.customCellClass.mainImage setImageWithURL:imageURL placeholderImage:nil];

每次单元格加载和下载同一图像时，您都将image=nil赋值

您可以使用以下类无缝地执行此操作

AsyncImageView.h

#import <UIKit/UIKit.h>


@interface AsyncImageView : UIView {
    NSURLConnection *connection;
    NSMutableData *data;
    NSString *urlString; // key for image cache dictionary
}

-(void)loadImageFromURL:(NSURL*)url;
-(void)loadBackgroundImage:(UIImage *)image;
-(UIImage*)loadImageFromURLForGetIamge:(NSURL*)url;
-(BOOL)getCachedImageWithUrl:(NSString*)url;

@end

使用
dispatch\u async
从远程加载图像，这意味着要在tableview单元格中显示的图像是异步加载的。您使用一个实例变量来记录当前单元格，这导致了您遇到的问题

图像加载完成后（可能需要几分钟），它希望显示在单元格中（用此代码编写）

结果发现，
self.customCellClass
指向错误的单元格（加载图像期间多次调用了
-（UITableViewCell*）cellForRowAtIndexPath:（NSIndexPath*）indexPath
，每次调用都会将
self.customCellClass
指向其他单元格）

所以，图像的顺序是错误的

试试这个：

使用局部变量保持单元格get from
dequeueReusableCellWithIdentifier
。像这样：

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:     (NSIndexPath *)indexPath
{
    CellCustom *customCellClass = (CellCustom *)[tableView dequeueReusableCellWithIdentifier:@"Cell"];
    if (customCellClass == nil)
    {
        customCellClass = [[CellCustom alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
    }
    customCellClass.nameLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"name"]; // label
    customCellClass.cityLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"region"]; // label

    NSString * stripped = [[[arrayData objectAtIndex:indexPath.row] objectForKey:@"summary"] stripHtml]; //label
    customCellClass.detailLabel.text = stripped;
    customCellClass.mainImage.image = nil;


    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
        NSData *data0 = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[[arrayData objectAtIndex:indexPath.row]objectForKey:@"images"]objectForKey:@"logo"]]];
        UIImage *image = [UIImage imageWithData:data0];

        dispatch_sync(dispatch_get_main_queue(), ^(void) {
            customCellClass.mainImage.image = image;
        });
    });
    return customCellClass;
}

此外，请看一下
-（id）dequeueReusableCellWithIdentifier:（NSString*）identifier
和
-（id）dequeueReusableCellWithIdentifier:（NSString*）indexath的标识符：（nsindexath*）之间的区别indexPath
当我滚动tableview图像后，应用程序首次启动图像为空，但顺序不正确我没有使用任何afnetworking框架如果我使用afnetworking框架，这很好，但在您需要进行http连接的整个项目中，可以使用afnetworking。什么是“XTest/XTest.h类”在将AFNetworking文件夹拖动到项目中后，未发现它在项目中拖动AFNetworking和UIKit+AFNetworking文件夹并导入#导入“AFNetworking.h”#导入“UIImageView+AFNetworking.h”你能告诉我我必须改变什么吗？是的，我试过了，但它对我不起作用，所以我使用了AFNetworking framework，现在一切对mesorry都很好，我没有试过给我一次机会，它对我不起作用图像以非常糟糕的方式出现，它们正在跳转到另一个位置，我用AFNetworking framework找到了任何解决方案，谢谢为了帮助我为什么不试试SDWebImage？@MaheshM
dispatch_sync(dispatch_get_main_queue(), ^(void) {
    self.customCellClass.mainImage.image = image;
});

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:     (NSIndexPath *)indexPath
{
    CellCustom *customCellClass = (CellCustom *)[tableView dequeueReusableCellWithIdentifier:@"Cell"];
    if (customCellClass == nil)
    {
        customCellClass = [[CellCustom alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
    }
    customCellClass.nameLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"name"]; // label
    customCellClass.cityLabel.text = [[arrayData objectAtIndex:indexPath.row] objectForKey:@"region"]; // label

    NSString * stripped = [[[arrayData objectAtIndex:indexPath.row] objectForKey:@"summary"] stripHtml]; //label
    customCellClass.detailLabel.text = stripped;
    customCellClass.mainImage.image = nil;


    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
        NSData *data0 = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[[arrayData objectAtIndex:indexPath.row]objectForKey:@"images"]objectForKey:@"logo"]]];
        UIImage *image = [UIImage imageWithData:data0];

        dispatch_sync(dispatch_get_main_queue(), ^(void) {
            customCellClass.mainImage.image = image;
        });
    });
    return customCellClass;
}