在我的iOS应用中，我在多个UITableViewCells内显示图片。但是，它没有在每个单元格中显示正确的图像。
首先，我使用以下方法从Feedly流加载一些内容：
- (void)loadStreams {
NSString *feedName = [NSString stringWithFormat:@"%@-id", self.category];
NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSString *accessToken = [standardUserDefaults objectForKey:@"AccessToken"];
NSString *feedId = [standardUserDefaults objectForKey:feedName];
NSString *feedPartial = [feedId stringByReplacingOccurrencesOfString:@"/" withString:@"%2F"];
NSString *feedUrl = [NSString stringWithFormat:@"https://sandbox.feedly.com/v3/streams/%@/contents", feedPartial];
NSLog(@"The Feedly url is: %@", feedUrl);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:feedUrl]];
NSMutableURLRequest *mutableRequest = [request mutableCopy];
[mutableRequest addValue:accessToken forHTTPHeaderField:@"Authorization"];
request = [mutableRequest copy];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSArray *jsonArray = (NSArray *)[responseObject objectForKey:@"items"];
self.continuation = [responseObject objectForKey:@"continuation"];
NSMutableArray *tempStreams = [[NSMutableArray alloc] init];
for (NSDictionary *dic in jsonArray) {
NSLog(@"Dic contains: %@", dic);
NSDictionary *originArray = [dic objectForKey:@"origin"];
NSDictionary *visualArray = [dic objectForKey:@"visual"];
NSArray *alternateArray = [dic objectForKey:@"alternate"];
NSDictionary *alternate = [alternateArray objectAtIndex:0];
NSString *image = [visualArray objectForKey:@"url"];
NSString *title = [dic objectForKey:@"title"];
NSString *author = [dic objectForKey:@"author"];
NSString *date = [dic objectForKey:@"published"];
NSDictionary *contentum = [dic objectForKey:@"content"];
NSString *content = [contentum objectForKey:@"content"];
NSString *owner = [originArray objectForKey:@"title"];
NSString *givenid = [dic objectForKey:@"id"];
NSString *href = [alternate objectForKey:@"href"];
NSDate *publisher = [NSDate dateWithTimeIntervalSince1970:([date doubleValue] / 1000.0)];
NSString *published = publisher.timeAgoSinceNow;
NSDictionary *data = [[NSDictionary alloc] initWithObjectsAndKeys:title, @"title", image, @"imageurl", published, @"published", owner, @"owner", content, @"content", givenid, @"givenid", href, @"href", author, @"author", nil];
Stream *stream = [[Stream alloc] initWithDictionary:data];
[tempStreams addObject:stream];
}
self.streams = [[NSMutableArray alloc] initWithArray:tempStreams];
tempStreams = nil;
[self.tableView reloadData];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Services"
message:[error localizedDescription]
delegate:nil
cancelButtonTitle:@"Ok"
otherButtonTitles:nil];
[alertView show];
}];
[operation start];
}
这会将数据传递给名为Stream的对象，该对象由以下代码组成：
Stream.h
#import <Foundation/Foundation.h>
@interface Stream : NSObject
@property (strong, nonatomic)NSString *name;
@property (strong, nonatomic)NSString *thumbnail;
@property (strong, nonatomic)NSString *photo;
@property (strong, nonatomic)NSString *published;
@property (strong, nonatomic)NSString *content;
@property (strong, nonatomic)NSString *givenid;
@property (strong, nonatomic)NSString *linky;
@property (strong, nonatomic)NSString *author;
- (id)initWithName:(NSString *)aName
thumbnail:(NSString *)aThumbnail
photo:(NSString *)aPhoto
published:(NSString *)aPublished
content:(NSString *)aContent
givenid:(NSString *)aId
linky:(NSString *)aLinky
author:(NSString *)aAuthor;
- (id)initWithDictionary:(NSDictionary *)dic;
@end
Stream.m
#import "Stream.h"
@implementation Stream
//The designed initializer
- (id)initWithName:(NSString *)aName
thumbnail:(NSString *)aThumbnail
photo:(NSString *)aPhoto
published:(NSString *)aPublished
content:(NSString *)aContent
givenid:(NSString *)aId
linky:(NSString *)aLinky
author:(NSString *)aAuthor{
self = [super init];
if (self) {
self.name = aName;
self.thumbnail = aThumbnail;
self.photo = aPhoto;
self.published = aPublished;
self.content = aContent;
self.givenid = aId;
self.linky = aLinky;
self.author = aAuthor;
}
return self;
}
- (id)initWithDictionary:(NSDictionary *)dic {
self = [self initWithName:dic[@"title"] thumbnail:dic[@"imageurl"] photo:dic[@"imageurl"] published:dic[@"published"] content:dic[@"content"] givenid:dic[@"givenid"] linky:dic[@"href"] author:dic[@"author"]];
return self;
}
- (id)init {
self = [self initWithName:@"Undifined" thumbnail:@"Undifined" photo:@"Undifined" published:@"Undifined" content:@"Undifined" givenid:@"Undifined" linky:@"Undifined" author:@"Undifined"];
return self;
}
@end
最后我构建了一个这样的单元格：
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString * reuseIdentifier = @"programmaticCell";
MGSwipeTableCell * cell = [self.tableView dequeueReusableCellWithIdentifier:reuseIdentifier];
if (!cell) {
cell = [[MGSwipeTableCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:reuseIdentifier];
}
CGFloat brightness = [UIScreen mainScreen].brightness;
cell.textLabel.text = [self.streams[indexPath.row] name];
cell.detailTextLabel.text = [self.streams[indexPath.row] published];
NSString *imageUrl = [NSString stringWithFormat: @"%@", [self.streams[indexPath.row] photo]];
NSLog(@"Image is: %@ and path is: %d", imageUrl, indexPath.row);
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:imageUrl]
placeholderImage:[UIImage imageNamed:@"tile-blue.png"] options:indexPath.row == 0 ? SDWebImageRefreshCached : 0];
cell.delegate = self; //optional
return cell;
}
但是，它会在很多单元格中显示错误的图像，有时在几个单元格中显示相同的图像。我在这里做错了什么？
答案 0 :(得分：1)
这些是细胞再利用的症状。您将需要处理两个问题。
（1）您应该在重复使用之前重置您的手机内容。要执行此操作，您可以覆盖单元格中的prepareForReuse，并取消相关属性（例如cell.imageView）。如果你不这样做，你会看到旧图像 - 在SDWebImage分配了新图像之前，单元格已被回收。
（2）由于SDWebImage图像检索是异步的，图像可能会在单元格滚动离开屏幕后到达（并使用新内容进行回收。在将图像指定给图像之前，您需要检查图像是否仍然相关imageView。我不确定使用SDWebImage UIImageView类别方法是否可行。您可能需要稍微剖析SDWebImage。您可以使用SDWebImageManager更好地控制流程方法：
- (id <SDWebImageOperation>)downloadImageWithURL:(NSURL *)url
options:(SDWebImageOptions)options
progress:(SDWebImageDownloaderProgressBlock)progressBlock
completed:(SDWebImageCompletionWithFinishedBlock)completedBlock;
您可以使用类似的内容（在CellForRowAtIndexPath）
[[SDWebImageManager defaultManager] downloadImageWithURL:url
options:0
progress:nil
completed:
^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if ([[tableView indexPathForCell:cell] isEqual:indexPath]) {
//image is still valid for this cell
cell.image = image;
}
}];
答案 1 :(得分：0)
prepareForReuse 像这样：
func updateArtistImage(url: URL) {
let _eventId = self.event?.id
SDWebImageManager.shared().loadImage(with: url, options: [], progress: nil) { (image, data, error, cacheType, finished, url) in
if self.event!.id == _eventId {
if error == nil {
self.artistImageView.image = image
} else {
self.artistImageView.image = UIImage(named: "error_image")
}
}
}
}
和此：
override func prepareForReuse() {
super.prepareForReuse()
self.artistImageView.image = nil
}