Shadow at the top of a Cell UITableCellView - iphone

Question

I wondered if anyone knows how to get a shadaow effect like the one in things as per the screenshot. To me it looks like the shadow effect is created by having a shadow at the bottom of the cell above and the top of the cell below.
I can create the one from the cell above using the code below but can't figure out how to do it on the cell underneath as it doesn't get shown it's as if the cells are rendered in reverse order in terms of the z-index.
self.layer.shadowOffset = CGSizeMake(0, 2);
self.layer.shadowColor = [[UIColor blackColor] CGColor];
self.layer.shadowRadius = 2;
self.layer.shadowOpacity = 0.5;
CGFloat top = self.layer.bounds.origin.y;
CGFloat left = self.layer.bounds.origin.x;
CGFloat width = self.layer.bounds.size.width;
CGRect shadowFrame = CGRectMake(left, top, width, 44);
CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:shadowFrame].CGPath;
self.layer.shadowPath = shadowPath;
Any suggestions much appreciated.
Things http://www.purplesmash.com/images/Things.jpg

Answer 1

Just create hollow rectangle while drawing with CoreGraphics (align it exactly that hollow part cover your cell visible view) and set shadow for context - this will save performance for you.
UPDATE:
I've tried this inside my cell drawRect: method
// Creating path which will hold our hollow rectangle
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectMake(-8.0f, -8.0f, 336.0f, 96.0f));
CGPathAddRect(path, NULL, CGRectMake(-5.0f, 0.0f, 330.0f, 80.0f));
// Saving current graphics context state
CGContextSaveGState(context);
// Configuring shadow
CGContextSetShadowWithColor(context, CGSizeMake(0.0f, 0.0f), 6.0f,
[[UIColor blackColor] CGColor]);
// Adding our path
CGContextAddPath(context, path);
// Configure hollow rectangle fill color
CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
// Fill rectangle and keep hollow part transparent
CGContextEOFillPath(context);
// Restore graphics context
CGContextRestoreGState(context);
Of course additional improvement will be pre-calculate CGMutablePathRef path somewhere in initialization or in this method by condition if(path == NULL). Colors can be retained too. If this should be last row of your cell update, than maybe you don't event need to save context state.

Answer 2

You probably need to do this by drawing the shadows as part of the checked cell instead of setting the shadow properties on the surrounding cells.
I'd do it by adding one or two CAGradientLayers as children of the checked cell's contentView.layer.

Answer 3

I have edited this in light of the suggestion from moonlight. I put that code into a method addInnerTopShadow when a cell needs that I call the method. I have added another method addInnerBottomShadow which puts in the shadow at the bottom.
I call these methods in the drawRect method and when I want to change between the states I call the method:
[cell setNeedsDisplay];
This allows me to toggle the state of the cell without doing things like
[self.tableView reloadData];
As the methods suggest I have outer shadow methods that put a shadow on the first and last cells but that's another issue and has been answered many times. I now have my app working exactly how I want. So thanks to Rob and Moonlight.
-(void)addInnerBottomShadow
{
CGContextRef context = UIGraphicsGetCurrentContext();
// Creating path which will hold our hollow rectangle
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectMake(0, 44, 480, 80));
CGPathAddRect(path, NULL, CGRectMake(0, 54, 480, 96));
// Saving current graphics context state
CGContextSaveGState(context);
// Configuring shadow
CGContextSetShadowWithColor(context, CGSizeMake(0.0f, 0.0f), 6.0f, [[UIColor blackColor] CGColor]);
// Adding our path
CGContextAddPath(context, path);
// Configure hollow rectangle fill color
CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
// Fill rectangle and keep hollow part transparent
CGContextEOFillPath(context);
CGContextClipToRect(context, self.bounds);
// Restore graphics context
CGContextRestoreGState(context);
}
-(void)addInnerTopShadow
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectMake(-8.0f, -8.0f, 336.0f, 96.0f));
CGPathAddRect(path, NULL, CGRectMake(-5.0f, 0.0f, 330.0f, 80.0f));
// Saving current graphics context state
CGContextSaveGState(context);
// Configuring shadow
CGContextSetShadowWithColor(context, CGSizeMake(0.0f, 0.0f), 7.0f, [[UIColor blackColor] CGColor]);
// Adding our path
CGContextAddPath(context, path);
// Configure hollow rectangle fill color
CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
// Fill rectangle and keep hollow part transparent
CGContextEOFillPath(context);
CGContextClipToRect(context, self.bounds);
// Restore graphics context
CGContextRestoreGState(context);
}