UIView inside an UIScrollView did not refresh itself despite call of method "setNeedDisplay" - ios

Question

I've got an UIScrollView with inside, some views loaded from a xib file.
The UIScrollView loads only three Views. The current, the left one and the right one.
For exemple, I have one view at the left and one view at the right of the current View. If I scroll to the right, the UIScrollView will delete the view to the left, scroll to the right to the new current View and load the new view to the right of the new current View.
In addition, I have a button outside the UIScrollView. When I click on it, it changes the background color of the current view displayed on the UIScrollView.
It works well but sometimes, I don't know why, when I click on the button to change the background color of the view is well changed, but the view is not refresh so the user can't see the change of background color.
The UIScrollView:
container = [[UIScrollView alloc] initWithFrame:frame];
[container setBackgroundColor:[UIColor clearColor]];
[container setCanCancelContentTouches:NO];
[container setClipsToBounds:NO];
[container setShowsHorizontalScrollIndicator:NO];
[container setPagingEnabled:YES];
The method call when I click on the button to change the background color of the current view
- (void)menuColor:(MenuPickerViewController *)controller didPickOption:(UIView *)button
{
// Get the object containing the data of the product linked with the view.
MyProduct *product = (MyProduct *)[MyProduct getProduct:[_slider getCurrentContentDisplayed]];
// Get the the superview of the button sender to have an access for the attributes of this button (color selected, ...)
ColorButtonMenu *colorView = (ColorButtonMenu *)[button superview];
// Get the current UIView displayed in the UIScrollView
MyView *myView = (MyView *)[self sliderGetViewWithID:[_slider getCurrentContentDisplayed] FromSlider:_slider];
// I check with debugger, the color is well setted
product.color = colorView.color;
// "border" is a view in my xib that I want change its background color.
IFPrint(#"myView.border backgorund color before: %#\n", myView.border.backgroundColor.description);
[myView.border setBackgroundColor:[Utilities colorFromHexString:colorView.color]];
[myView.border setNeedsDisplay];
IFPrint(#"myView.border backgorund color after: %#\n", myView.border.backgroundColor.description);
IFPrint(#"=== DEBUG ===\n");
IFPrint(#"isMainThread ? : %i\n", [NSThread isMainThread]); // Always return YES
IFPrint(#"myView: %#\n", myView); // Always return the address of a valid pointer
IFPrint(#"myView border: %#\n", myView.border); // Always return the address of a valid pointer
IFPrint(#"=============\n\n");
}
So, as you can see at the end of the method, I tried to call method setNeedsDisplay on the view loaded from a xib and the other view inside "border" but nothings work.
Moreover, my method is always called on the main thread.
Any suppositions ?
Thanks !
Edit:
Obviously, I have tested if the view return by sliderGetViewWithID is the correct view. All the attributes are well set. In my opinion it's truly a refresh problem.

Answer 1

are you sure the view you're trying to set background color for is actually visible? I guess it might be offscreen so you see nothing happening.
You might want to trap that event by finding the intersection between scrollview's bounds and myView's frame. if there's no intersection, that means myView is not actually visible.
so the code is:
BOOL intersects = CGRectIntersectsRect(scrollview.bounds, myView.frame);
if(intersects == NO)
{
NSLog(#"myView is offscreen");
}

Answer 2

Problem solved :
After setting the background color of the view. I remove the view from the UIScrollView and I re add it inside the UIScrollView. It's a bit tricky but it works good !
[myView removeFromSuperView];
[myScrollView addSubview:myView];