我有一个UITableView，它有一个后台UIImageView。很少有细胞将图像作为背景而其他细胞则没有。我面临的问题是，有时（在滚动和重复使用单元格时），错误的图像出现在错误的单元格上。在这种情况下，我将文本颜色更改为白色。在某些情况下，图像不会加载，但文本已经转换为白色。这导致普通单元格作为背景，文本颜色为白色。这不会一直发生。但它确实发生了。这就是我在cellForAtIndexPath中所做的事情：
// Image
if ((NSNull*) imageString != [NSNull null])
{
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:imageString]];
[cell.questionImageView setImageWithURLRequest:request placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
NSArray *array = [self.tableView indexPathsForVisibleRows];
BOOL visible = NO ;
for (NSIndexPath *ipath in array) {
if (ipath.row == indexPath.row) {
visible = YES ;
break ;
}
}
if (visible)
{
QuestFeedTableViewCell *recreateCell = (QuestFeedTableViewCell*)[self.tableView cellForRowAtIndexPath:indexPath];
recreateCell.question.textColor = [UIColor whiteColor];
recreateCell.questionImageView.contentMode = UIViewContentModeScaleAspectFill;
UIColor *tintColor = [UIColor colorWithWhite:0.3 alpha:0.6];
_postImage = image;
recreateCell.questionImageView.alpha = 0.8;
recreateCell.questionImageView.image = image;
[recreateCell.questionImageView setClipsToBounds:YES];
if (image)
{
recreateCell.question.textColor = [UIColor whiteColor];
recreateCell.question.tintColor = [UIColor whiteColor];
recreateCell.answersCount.textColor = [UIColor whiteColor];
recreateCell.answersCount.tintColor = [UIColor whiteColor];
}
[recreateCell setNeedsLayout];
[recreateCell.questionImageView setNeedsDisplay];
}
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error)
{
cell.questionImageView.image = nil;
cell.question.textColor = [UIColor colorWithRed:77.0f/255.0f green:85.0f/255.0f blue:100.0f/255.0f alpha:1.0f];
cell.question.tintColor = [UIColor colorWithRed:77.0f/255.0f green:85.0f/255.0f blue:100.0f/255.0f alpha:1.0f];
[cell setNeedsDisplay];
}];
}
else
{
cell.questionImageView.image = nil;
cell.question.textColor = [UIColor colorWithRed:77.0f/255.0f green:85.0f/255.0f blue:100.0f/255.0f alpha:1.0f];
cell.question.tintColor = [UIColor colorWithRed:77.0f/255.0f green:85.0f/255.0f blue:100.0f/255.0f alpha:1.0f];
cell.answersCount.textColor = [QuestUtility colorFromHexString:@"#757b86"];
cell.answersCount.tintColor = [QuestUtility colorFromHexString:@"#757b86"];
}
这个问题不会一直发生。什么是最好的解决方案？为这两个创建单独的XIB？
答案 0 :(得分：0)
你知道重用细胞机制。因此，有可能在单元格索引为1时获取图像，但单元格在索引为6时出列，例如，其背景已更改。
您应该将indexPath保留在成功块中，当成功块回调时，检查indexPath是否在tableview的indexPathsForVisibleRows数组中，如果是，则使用cellForRowAtIndexPath:indexPath方法获取单元格将图像分配给imageView和其他操作...
我有一个关于UICollectionView的项目示例，我认为这会有所帮助。在项目中，我使用UICollectionView而不是UITableView，但它在基础上是相同的。我在另一个线程上获取UIImage，然后将其分配给单元格的imageView。
Image *image = (Image *)multimedium ;
NSString *thumbnaiPath = image.thumbnailPath ;
UIImage *imageObj = _thumbnailImageCache[thumbnaiPath] ;
if (!imageObj) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// I omit some time consuming work to get the data
UIImage *thumbnail = [UIImage imageWithData:data] ;
dispatch_async(dispatch_get_main_queue(), ^{
_thumbnailImageCache[thumbnaiPath] = thumbnail ;
NSArray *array = [_collectionView indexPathsForVisibleItems] ;
BOOL visible = NO ;
for (NSIndexPath *ipath in array) {
if (ipath.row == indexPath.row) {
visible = YES ;
break ;
}
}
if (visible) {
UICollectionViewCell *cell = [_collectionView cellForItemAtIndexPath:indexPath] ;
UIImageView *view = (UIImageView *)[cell.contentView viewWithTag:imageViewTag] ;
view.image = thumbnail ;
}
}) ;
}) ;
} else {
imageView.image = imageObj ;
}
答案 1 :(得分：0)
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
if ((NSNull*) imageString != [NSNull null])
{
cell.questionImageView.contentMode = UIViewContentModeScaleAspectFill;
//get a dispatch queue
dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
//this will start the image loading in bg
dispatch_async(concurrentQueue, ^{
NSData *image = [[NSData alloc] initWithContentsOfURL:imageString];
//this will set the image when loading is finished
dispatch_async(dispatch_get_main_queue(), ^{
cell.questionImageView = [UIImage imageWithData:image];
});
});
}
}
您还可以关注以下网址“UITableView repeating cells when scrolled”
答案 2 :(得分：0)
在viewWillAppear中分配init storeIndexArray
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *cellIdentifier = @"Cell Identifier";
TimeSheetCell *cell=[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell) {
cell = [[TimeSheetCell alloc]initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:cellIdentifier];
cell.accessoryType = UITableViewCellAccessoryNone;
}
cell.selectionStyle = UITableViewCellSelectionStyleNone;
if ([self.storeIndexArray containsObject:indexPath])
{
[cell.checkImage setImage:[UIImage imageNamed:@"check_box_selected.png"]];
}
else
{
[cell.checkImage setImage:[UIImage imageNamed:@"check_box.png"]];
}
cell.timeSheetModel = [self.timeSheetListArray objectAtIndex:indexPath.row];
return cell;
}
- (void)tableView:(UITableView *)tableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
TimeSheetCell *cell = (TimeSheetCell*)[tableView cellForRowAtIndexPath:indexPath];
[self.storeIndexArray addObject:indexPath];
[cell.checkImage setImage:[UIImage imageNamed:@"check_box_selected.png"]];
}
- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath {
TimeSheetCell *cell = (TimeSheetCell*)[tableView cellForRowAtIndexPath:indexPath];
[self.storeIndexArray removeObject:indexPath];
[cell.checkImage setImage:[UIImage imageNamed:@"check_box.png"]];
}