Ios UITableView单元格在快速滚动时显示相同的图像

我正在创建iPhone应用程序，它在表视图中显示应用程序图标和应用程序名称

我第一次下载用户文档目录中的图像，然后在字典中输入[值-图像存储文档目录路径和键是图像json URL]，首先在单元格中显示图像，我检查图像是否已下载

如果已下载，则显示存储在文档目录中的本地映像，如果未下载，则下载

如果我正常滚动，单元格将显示正确的图像&如果我快速滚动，单元格将显示相同的图像，而不是不同的图像

// code for displaying images

-(void)refreshViews
{

self.appLabelName.text = _applicationObject.name;
self.appLabelName.font = [UIFont fontWithName:@"Helvetica-Bold" size:17];
self.detailTextLabel.text = _applicationObject.artistName;
self.detailTextLabel.font = [UIFont fontWithName:@"Helvetica" size:14];


NSString *appIconStoredPath = [appDelgate.saveAppIconURLAndPathInFile valueForKey:_applicationObject.iconURL];
_appIcon.image = [UIImage imageWithContentsOfFile:appIconStoredPath];

if(!_appIcon.image && appDelgate.hasInternetConnection)
{
    [self downloadAppIconsInDirectory];
}
}

// code for download image

-(void)downloadAppIconsInDirectory
{
NSURL *downloadURL = [NSURL URLWithString:_applicationObject.iconURL];

NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig delegate:nil delegateQueue:nil];

__weak  ApplicationCell* weakSelf = self;

dispatch_async(queue, ^{

    downloadTask = [session downloadTaskWithURL:downloadURL completionHandler:^(NSURL *location,  NSURLResponse *respone, NSError *error)
          {
              NSString *iconName = [location lastPathComponent];
              NSMutableString *changeIconName = [[NSMutableString alloc] init];

              changeIconName = [iconName mutableCopy];

              [changeIconName setString:_applicationObject.bundleId];![enter image description here][1]

              NSString *appIconDirectory = [[documentsDirectoryForAppIcons absoluteString] stringByAppendingPathComponent:@"appIcons"];

              destinationUrlForAppIcons = [[NSURL URLWithString:appIconDirectory] URLByAppendingPathComponent:changeIconName];

              NSError *error1;

              BOOL status = [appIconFileManager copyItemAtURL:location toURL:destinationUrlForAppIcons error:&error1];
              if (status && !error1)
                  {
                      dispatch_async(dispatch_get_main_queue(), ^{
                      [weakSelf refreshViews];
                      });

                      [appDelgate.saveAppIconURLAndPathInFile setValue:destinationUrlForAppIcons.path forKey:_applicationObject.iconURL];

                      NSString *dictSavedFilePath = [appDelgate.documentDirectoryPath stringByAppendingPathComponent:@"IconURLsAndPaths.plist"];

                      dispatch_async(queue, ^{
                      [appDelgate.saveAppIconURLAndPathInFile writeToFile:dictSavedFilePath atomically:YES];
                      });
                  }

          }];
    [downloadTask resume];
});
}

---

如图所示，代码中没有错误。这意味着您认为队列的优先级是错误的。在滚动之前必须下载图像。当你们慢慢地滚动你们的视图时，图像会有足够的时间被下载。这意味着您将代码更改为此，然后重试；）

---

将refreshViews方法替换为此

    -(void)refreshViews
    {

        self.appLabelName.text = _applicationObject.name;
        self.appLabelName.font = [UIFont fontWithName:@"Helvetica-Bold" size:17];
        self.detailTextLabel.text = _applicationObject.artistName;
        self.detailTextLabel.font = [UIFont fontWithName:@"Helvetica" size:14];

        _appIcon.image = nil;
        NSString *appIconStoredPath = [appDelgate.saveAppIconURLAndPathInFile valueForKey:_applicationObject.iconURL];
        _appIcon.image = [UIImage imageWithContentsOfFile:appIconStoredPath];

        if(!_appIcon.image && appDelgate.hasInternetConnection)
        {
            [self downloadAppIconsInDirectory];
        }
    }

---

它会加载上一个图像，因为tableview会重用单元格，所以imageview也会重用保存上一个图像的单元格。因此，您必须对该图像执行nil操作

您需要显示UITableView委托方法的代码，以便我们可以看到您如何尝试使用该图像如果我们制作_appIcon.image=nil；它不起作用。我检查了字典内容，不同的图像URL（键）有相同的图像本地路径（值）如果我们将appIcon设为零，则不会影响任何内容。bcoz字典内容错误的图像本地路径。为了避免此问题，我使用NSURLSession委托而不是完成块。参考链接：如果我们在将内容保存到字典之前调用refreshViews方法，这并不能解决问题。有解决这个问题的其他解决方案吗？：）我认为您必须在将内容保存到字典中之后调用RefreshView，而不是之前。

    -(void)refreshViews
    {

        self.appLabelName.text = _applicationObject.name;
        self.appLabelName.font = [UIFont fontWithName:@"Helvetica-Bold" size:17];
        self.detailTextLabel.text = _applicationObject.artistName;
        self.detailTextLabel.font = [UIFont fontWithName:@"Helvetica" size:14];

        _appIcon.image = nil;
        NSString *appIconStoredPath = [appDelgate.saveAppIconURLAndPathInFile valueForKey:_applicationObject.iconURL];
        _appIcon.image = [UIImage imageWithContentsOfFile:appIconStoredPath];

        if(!_appIcon.image && appDelgate.hasInternetConnection)
        {
            [self downloadAppIconsInDirectory];
        }
    }