SetNeedsDisplay in table view - objective-c

Question

My problem is that not all cell are correct initialized with the correct UIView as an rendered image.( see code below) On a iphone 4 it always the same cel on a iphone with retina display is also an other cell. In this set-up setNeedsDisplay won't function.
If i use the same structure in an IBoutlet it's working.
!
I need to use in some cells the image-files .png and at some other cells the defined drawing method, which uses the drawrect or better i should use the setNeedsDisplay method.....
What is going wrong!!!
my code
tableview... cell
static NSString *CellIdentifier = #"TypeCell";
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// Configure the cell...
CellTypes *cellType = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.textLabel.text = cellType.title;
cell.detailTextLabel.text = cellType.detail;
if ( [cellType.type rangeOfString:#"TL"].location != NSNotFound) {
cell.imageView.image = [UIImage imageNamed:[cellType.type stringByAppendingString:#"Thumb"]];
cell.indentationWidth = 10;
}
else {
static CGFloat scale = 0.0; // old API , screen values
UIScreen *screen = [UIScreen mainScreen];
if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 4.0) {
scale = [screen scale];
}
if (scale>0.0) {
UIGraphicsBeginImageContextWithOptions(cell.imageView.bounds.size, NO, scale);
}
else {
UIGraphicsBeginImageContext(cell.imageView.bounds.size);
}
CGRect imageRect = CGRectMake(0, 0, 84, 84 ); // cell.imageView.bounds;
FittingImageView *fittingImage = [[FittingImageView alloc] initWithFrame:imageRect];
fittingImage.thumb = YES;
fittingImage.title = offSetType.title;
[fittingImage drawRect:imageRect]; // this works but skips one imageRect
// [fittingImage setNeedsDisplay]; //this won't work.
[cell.layer renderInContext:UIGraphicsGetCurrentContext()];
cell.imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
return cell;

Answer 1

You can never call drawRect: yourself. It is called by Cocoa, and only Cocoa can setup the context. It's unclear what you're trying to do here. I don't know what a FittingImageView is. You're creating it and then throwing it away in any case.
You then try to render the cell itself into an image, and the put that image into the cell's imageview. That doesn't make sense.
You may misunderstand how tableview cells are created, reused and drawn. You should re-read "Creating and Configuring a Table View."
The primary things to remember:
In this routine, your job is to either create a new cell, or reconfigure a reusable cell (if dequeueReusableCellWithIdentifier: returns you something).
This routine is not for drawing a cell. That will happen much later, and it is the cell's job to draw itself. You're just configuring the cell. Putting everything in it that it needs to draw later.
You typically do not want to compute expensive things in this routine. Compute those elsewhere and cache them. This routine should configure a cell, slap data into it, and return. If you try to create new images in this routine, your table view is going to stutter.
You shouldn't mess with the cell's layer in the middle of this routine. If you need something that complex, you should be creating a custom cell with its own drawRect:.