why the table view cells are messed up after refreshing some rows? - ios

Question

I am using UITableView to list some images from Internet. So i use AFNetworking's setImageWithURLRequest:placeholderImage:success:failure:methord, when the image is downloaded, i need to do some process then display. In order to refresh the processed image i use
[wTableView beginUpdates];
[wTableView reloadRowsAtIndexPaths:[NSArray arrayWithObjects:indexPath, nil] withRowAnimation:UITableViewRowAnimationNone];
[wTableView endUpdates];
in the success block. It seems this works when first time loaded, but when i scroll the tableview, the rows are messed up, also one row is disappeared and its easy to crash in the [wTableView endUpdates]; method. what's wrong with this method?
The related code snippet is as follows:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *tableIdentifier = #"cell";
CouponTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:tableIdentifier];
if (!cell) {
cell = [[CouponTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:tableIdentifier];
}
[cell prepareForReuse];
NSArray *coupons = [mCoupons objectAtIndex:indexPath.section];
CouponDB *couponDB = [coupons objectAtIndex:indexPath.row];
NSString *thumbLink;
if (couponDB) {
[cell.textLabel setText:couponDB.couponInfo.company];
[cell.textLabel setFont:[UIFont boldSystemFontOfSize:CELL_LABEL_FONT_SIZE]];
[cell.textLabel setTextColor:[UIColor grayColor]];
[cell.textLabel setBackgroundColor:[UIColor clearColor]];
[cell.detailTextLabel setText:[NSString stringWithFormat:#"Expires:%#",couponDB.couponInfo.deadline]];
[cell.detailTextLabel setBackgroundColor:[UIColor clearColor]];
thumbLink = [self thumbLink:couponDB.couponInfo.imgURL];
[cell setNeedsLayout];
if (couponDB.redeem_status) {
UIImageView * __weak imageView = cell.imageView;
CouponTableController * __weak table = self;
UITableView *__weak wTableView = mTableView;
[cell.imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:thumbLink]] placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
imageView.image = [table crossedImage:image];
#synchronized(wTableView){
[wTableView beginUpdates];
[wTableView reloadRowsAtIndexPaths:[NSArray arrayWithObjects:indexPath, nil] withRowAnimation:UITableViewRowAnimationNone];
[wTableView endUpdates];
}
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
NSLog(#"cell imageview load error:%#",error);
}];
} else {
[cell.imageView setImageWithURL:[NSURL URLWithString:thumbLink] placeholderImage:[UIImage imageNamed:#"default_cover.jpg"]];
}
}
if (![cell.backgroundView isKindOfClass:[CouponTableCellBackgroud class]]) {
cell.backgroundView = [[CouponTableCellBackgroud alloc] init];
}
return cell;
}
the first time the table is loaded(no scroll) is like this:
when you scroll down and up the table rows are messed up, which is like below:
Any suggestions are appreciated.

Answer 1

Try this, instead of reloading the cell. Declare a weak pointer to the cell
__weak UITableViewCell *weakCell = cell;
[cell.imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:thumbLink]] placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
weakCell.imageView.image = [table crossedImage:image];
[weakCell setNeedsLayout];
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
NSLog(#"cell imageview load error:%#",error);
}];

Answer 2

Can you try this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *SimpleTableIdentifier = #"YourResuseIdentifier";
CouponTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:tableIdentifier];
if(cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:SimpleTableIdentifier];
}
else
{
for (UIView *subview in cell.contentView.subviews)
[subview removeFromSuperview];
}
NSArray *coupons = [mCoupons objectAtIndex:indexPath.section];
CouponDB *couponDB = [coupons objectAtIndex:indexPath.row];
NSString *thumbLink;
if (couponDB) {
[cell.textLabel setText:couponDB.couponInfo.company];
[cell.textLabel setFont:[UIFont boldSystemFontOfSize:CELL_LABEL_FONT_SIZE]];
[cell.textLabel setTextColor:[UIColor grayColor]];
[cell.textLabel setBackgroundColor:[UIColor clearColor]];
[cell.detailTextLabel setText:[NSString stringWithFormat:#"Expires:%#",couponDB.couponInfo.deadline]];
[cell.detailTextLabel setBackgroundColor:[UIColor clearColor]];
thumbLink = [self thumbLink:couponDB.couponInfo.imgURL];
if (couponDB.redeem_status) {
UIImageView * __weak imageView = cell.imageView;
CouponTableController * __weak table = self;
UITableView *__weak wTableView = mTableView;
[cell.imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:thumbLink]] placeholderImage:nil success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
imageView.image = [table crossedImage:image];
[wTableView beginUpdates];
[wTableView reloadRowsAtIndexPaths:[NSArray arrayWithObjects:indexPath, nil] withRowAnimation:UITableViewRowAnimationNone];
[wTableView endUpdates];
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
NSLog(#"cell imageview load error:%#",error);
}];
} else {
[cell.imageView setImageWithURL:[NSURL URLWithString:thumbLink] placeholderImage:[UIImage imageNamed:#"default_cover.jpg"]];
}
}
if (![cell.backgroundView isKindOfClass:[CouponTableCellBackgroud class]]) {
cell.backgroundView = [[CouponTableCellBackgroud alloc] init];
}
return cell;
}

Answer 3

I change the load image code to
UIImageView * __weak imageView = cell.imageView;
CouponTableController * __weak table = self;
[cell.imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:thumbLink]] placeholderImage:[UIImage imageNamed:#"default_cover.jpg"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
imageView.image = [table crossedImage:image];
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
NSLog(#"cell imageview load error:%#",error);
}];
Only add one placeholder image and remove the tableview updates. then it refresh cells automatically.