Static UITableView appear disabled opaque alpha not working - ios

Question

I have a classic UITableViewController in an iOS 6.1 application. The table view is static and set in storyboard and it meant to represent configurable settings using UITableViewCellAccessoryCheckmark as ON/OFF switch. There is a section in TableView that disables another cell based on other setting. The cell is disabled with the following code:
cell.userInteractionEnabled = NO;
cell.textLabel.backgroundColor = [UIColor clearColor];
cell.alpha = 0.4;
The code is working fine once the TableView is loaded.
The problem is when TableView is loaded, the disabled cell code is not working correctly, because alpha setting in code does not work. UserInteractionEnabled property is working, but not the alpha setting.
This is code that should disable UITableViewCell when the view is loaded.
- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell* cell = [super tableView:tableView cellForRowAtIndexPath:indexPath];
if (cell)
{
...
if ([[self currentSettingForIndexPath:indexPath] isEqualToString:#"myDependencySetting"])
{
...
cell.userInteractionEnabled = NO;
cell.textLabel.backgroundColor = [UIColor clearColor];
cell.alpha = 0.4;
NSLog(#"Disabling cell: %0.2f", cell.alpha);
...
}
else
{
cell.alpha = 1.0;
cell.userInteractionEnabled = YES;
}
}
NSLog(#"Cell alpha: %0.2f", cell.alpha);
return cell;
}
The code here is fairly simple, I ask the super for cell (since self is subclass of UITableViewController, it shouldn't be a problem), then configure the cell. If cell on current index path depends on another setting, I disable the cell (I stripped some other lines of code that are irrelevant).
The output reads:
...
Cell alpha: 1.00
...
Cell alpha: 1.00
Disabling cell: 0.40
Cell alpha: 0.40
Cell alpha 1.00
...
So according to output the alpha property of the cell is set correctly. But the cell alpha is not set, however the cell is not tappable because of userInteractionEnabled.
The same code works for disabling the cell in tableView's delegate didSelectRowAtIndex.
The question is: Why and what could override the cell's alpha value?
Thank you.

Answer 1

So I know it's two years down the road, but I grappled a bit with the same exact problem as you and stumbled across this question. I happen to be using iOS 8, but the problem seems the same: I've got a static table view with a couple of cells whose alpha I'd like to adjust on initial table view setup. Making these adjustments in cellForRowAtIndexPath did not work. Each cell adjusted showed on screen with an alpha of 1.0, although I was logging their alphas at 0 in cellForRowAtIndexPath.
Since I was interested in adjusting all cells of a single section, I was able to obtain the desired functionality by including something along these lines in viewWillAppear:
- (void)changeAlphaOfCells:(float)alpha
{
for (int i = 0; i < NUMBER_OF_ROWS_IN_SECTION; i++)
{
UITableViewCell *cell = [[self tableView] cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:SECTION_NUMBER]];
cell.alpha = alpha;
}
}
You'll need logic to determine which cells to adjust the alpha of in viewWillAppear, and retrieve them with cellForRowAtIndexPath. Not as elegant as a single line call in cellForRowAtIndexPath, but not too bad.

Answer 2

I think you cant access the cell's alpha directly like that. Try this
EDIT:
UIColor *colorWithAlphaOfPointFour = [UIColor colorWithRed:0 green:0 blue:0 alpha:.4];
[[cell contentView] setBackgroundColor:[UIColor colorWithAlphaOfPointFour]];
[[cell backgroundView] setBackgroundColor:[UIColor colorWithAlphaOfPointFour]];
[cell setBackgroundColor:[UIColor colorWithAlphaOfPointFour]];