White screen then scrolling uitableview - ios

Question

Im using storyboards with prototypecells what looks like:
after that im adding dynamic count of subviews:
white screen
uitableviewcell in app
Problem what sometimes white screen appears on half of uitableviewcell then scrolling.
And cell==nil not called.
Or just explain how to add dynamic count of subviews to uitableviewcell.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellIdentifer;
cellIdentifer = #"PhotoWorkCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifer];
if (cell == nil){
NSLog(#"is nil");
}
[self addSubviews:cell atIndexPath:indexPath];
[self configureCell:cell atIndexPath:indexPath];//just setting images and text to views
return cell;
}
-(void)addSubviews:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath{
PhotoWork *work = [self.tableData objectAtIndex:indexPath.row];
PhotoWorkCell *workCell = (PhotoWorkCell*)cell;
for(UIView *view in workCell.contentView.subviews){
if ([view isKindOfClass:[CustomPoints class]])
[view removeFromSuperview];
}
for(int i=0; i <[work.pointsArray count];i++)
{
NSArray *subviewArray = [[NSBundle mainBundle] loadNibNamed:#"CustomPoints" owner:self options:nil];
CustomPoints *customPoints = [subviewArray objectAtIndex:0];
customPoints.frame = CGRectMake(10, 135+i*customPoints.frame.size.height, customPoints.frame.size.width, customPoints.frame.size.height);
customPoints.label= #"test";
workCell.photoButton.tag = indexPath.row;
[workCell.photoButton addTarget:self action:#selector(onHistory:) forControlEvents:UIControlEventTouchDown];
[workCell.contentView addSubview:customPoints];
}
}
- (CGFloat)tableView:(UITableView *)t heightForRowAtIndexPath:(NSIndexPath *)indexPath {
PhotoWork *work = [self.tableData objectAtIndex:indexPath.row];
return 135+[work.pointsArray count]*57;
}

Answer 1

From Apple's documentation of the dequeueReusableCellWithIdentifier: method:
This method dequeues an existing cell if one is available or creates a new one using the class or nib file you previously registered. If no cell is available for reuse and you did not register a class or nib file, this method returns nil.
This means that, if a cell with that identifier exists, the method will never return nil, but will rather initialise the cell for you through the initializer method initWithStyle:reuseIdentifier:.
Then from the documentation of the UITableViewCell's method prepareForReuse:
The table view's delegate in tableView:cellForRowAtIndexPath: should always reset all content when reusing a cell.
Which means that you should remove the additional subviews it might have before adding the new ones in your addSubviews:atIndexPath: method.
You could simply do:
NSMutableArray* tmpArray = [NSMutableArray arrayWithArray:workCell.contentView.subviews];
Then, assuming that the only extra subview you add to contentView is this CustomPoints, just do:
[tmpArray removeObject:tmpArray.lastObject];
workCell.contentView.subviews = tmpArray;
If, instead, you want to be safe just do:
__block NSInteger foundIndex = NSNotFound;
[tmpArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:[CustomPoints class]]) {
foundIndex = idx;
// stop the enumeration
*stop = YES;
}
}];
if (foundIndex != NSNotFound){
[tmpArray removeObjectAtIndex:foundIndex];
workCell.contentView.subviews = tmpArray;
}
Let me know if this worked for you!