ios - UINavigationController Bar color update in viewWillAppear updating after visible -

in app working on, have uitabbarcontroller contains views each in uinavigationcontroller.

one of views settings screen user can change color scheme of app. when so, , switch screen, every component supposed change color changed except background of uinavigationcontroller. updates fraction of second after visible, there annoying flicker.

this simplification of viewwillappear (which tested make sure still causes error)

- (void)viewwillappear:(bool)animated {     [super viewwillappear:animated];      uicolor *foreground = [self.settings getforegroundcolor];     uicolor *background = [self.settings getbackgroundcolor];      self.navigationcontroller.navigationbar.bartintcolor = background;     self.navigationcontroller.tabbarcontroller.tabbar.bartintcolor = background;     self.view.backgroundcolor = background;      self.navigationcontroller.navigationbar.tintcolor = foreground;     self.navigationcontroller.tabbarcontroller.tabbar.tintcolor = foreground;     self.view.tintcolor = foreground; } 

what stranger, have uibarbuttonitem in uinavigationcontroller bar go to, , it's color has updated before view visible, background behind still needs update.

things have tried:

• [self.view setneedsdisplay];
• [self.navigationcontroller.navigationbar setneedsdisplay];
• viewwilllayoutsubviews
• doing either of nsnotification sent viewcontroller when user changed color setting (long before click tab bar @ offending viewcontroller).

is there way force draw off screen, or flicker won't occur? not understand why insisting on updating when visible, when put in main viewcontroller's viewwillappear.

does know how make uinavigationcontroller's bar update before coming onscreen when uinavigationcontroller embedded in tab bar controller?