Loading many records in UITableView - ios

Question

I am loading a UITableView in this way:
- (UITableViewCell *)tableView:(UITableView *)tableViewLocal cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
CustomTableViewCell *cell = [tableViewLocal dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[CustomTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
for(UIView *subview in cell.contentView.subviews)
{
[subview removeFromSuperview];
}
UIImage* img;
UIImageView *imv = [[UIImageView alloc]initWithFrame:CGRectMake(5, 5, 60, 60)];
if(isFiltered == TRUE){
cell.textLabel.text = [filteredTableData objectAtIndex:indexPath.row];
cell.textLabel.font = [UIFont systemFontOfSize:14];
}
if(isFiltered == FALSE){
cell.textLabel.text = [itemArray objectAtIndex:indexPath.row];
cell.textLabel.font = [UIFont systemFontOfSize:14];
cell.detailTextLabel.text = [NSString stringWithFormat:#"date added: %#", [DKStoreManager dateFileWasCreatedWithFileName:[itemArray objectAtIndex:indexPath.row] inFolderNumber:[_FolderCode intValue] forUser:[_PassedUserID intValue] andType:_FolderType]];
}
NSData* data = [DKStoreManager loadFileWithName:[itemArray objectAtIndex:indexPath.row] forFolderNumber:[_FolderCode intValue] forUser:userID andType:_FolderType];
img = [[UIImage imageWithData:data] cropToSize:CGSizeMake(320, 320) usingMode:NYXCropModeCenter];
imv.image = img;
[cell.contentView addSubview:imv];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}
As you can see I have an itemArray with all the names of the files, and for each cell I load the relative NSData in this way:
NSData* data = [DKStoreManager loadFileWithName:[itemArray objectAtIndex:indexPath.row] forFolderNumber:[_FolderCode intValue] forUser:userID andType:_FolderType];
Since it also loads images (and there may be more than 300 cells), the UI frees.
I have tried loading only the visible cells using the accepted answer of this link:
tableView: cellForRowAtIndexPath: get called not only for visible cells?
however all of the cells are loaded at the same time. I have no idea of how to do this...

Answer 1

cellForRowAtIndexPath gets called when the tableView reloads as well as when the user scrolls. The UI freeze could be due to the fact that your calling
for(UIView *subview in cell.contentView.subviews)
{
[subview removeFromSuperview];
}
UIImageView *imv = [[UIImageView alloc]initWithFrame:CGRectMake(5, 5, 60, 60)];
which means that every time the user scrolls , you are iterating through all the subViews and removing them, as well as allocating UIimageView's at the same time, this is not a good way to go about displaying content. You can use the tableViewCell's default imageView property to display your image. After getting you image just say
cell.imageView.image = img;