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iphoneuitableviewclipping

Adding a subview larger than cellHeight to a UITableViewCell?

I'm trying to add a subview to a UITableViewCell and the design that I'm working from demands that this particular subview (an image) needs to be larger than the actual UITableViewCell and thus partly overlap its siblings.

So I've set up my table cell, generated my image and added it to the cell's contentView:

// rowHeight for the UITableView is 45.0f

UIImage *image = [self createCellThumbnail: someImage];
UIImageView *thumbView = [[UIImageView alloc] initWithFrame: CGRectMake(150, -5, 55,55)];
thumbView.transform = CGAffineTransformMakeRotation(0.1f);
thumbView.image = image;

cell.clipsToBounds = NO;
cell.contentView.clipsToBounds = NO;

[cell.contentView addSubview: thumbView];

While the image will 'overflow' into the cell below it, the top of the image is always clipped, as demonstrated here:

img

Does anyone know if what I'm trying to do is possible with the current approach?

Or should I just figure out a way to draw these images onto the UITableView after all the cells are drawn (it's a non-scrollable tableview, so that would work and be fairly easy).

Update:

Have also tried adding the following, to no avail:

cell.opaque = NO;
cell.contentView.opaque = NO;

cell.clearsContextBeforeDrawing = NO;
cell.contentView.clearsContextBeforeDrawing = NO;

cell.clipsToBounds = NO;    
cell.contentView.clipsToBounds = NO;
Solution

  • I seems that the tableView renders its cell from bottom to top, so the cells above one cell overlap that one cell. To avoid this, you'd have to set the backgroundColor of all cells to +[UIColor clearColor] so that you won't see those overlap problems.

    But setting the backgroundColor to clear in -tableView:cellForRowAtIndexPath: does not make any sense. UIKit does a lot of stuff with the cell before it's drawn, so does it reset the backgroundColor property of the cell.

    What we need to do is setting the backgroundColor in a later state. Luckily there is this -[UITableViewDelegate tableView:willDisplayCell:forRowAtIndexPath:] which we can implement like this:

    - (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    cell.backgroundColor = [UIColor clearColor];
}

    Now we're setting the backgroundColor just before the cell is drawn an this turns out to be working.