objective c - iOS change document picker status bar color not change -

my init viewcontroller show status bar tint color white color.

i need click alertertaction, presentviewcontroller uidocumentpickerviewcontroller status bar tint color changed the black color.

 ...    cloudaction = [uialertaction                actionwithtitle:@"from cloud"                style:uialertactionstyledefault                handler:^(uialertaction * action)                {                  [uinavigationbar appearance].tintcolor = [uicolor blackcolor];                      [self presentviewcontroller:cloudpicker animated:yes completion:nil];                 }];  ... 

and viewwillappear method set

 -(void) viewwillappear:(bool)animated{           [super viewwillappear:animated];                [uinavigationbar appearance].tintcolor = [uicolor whitecolor];        } 

it strange. when click alert, show cloud picker(uidocumentpickerviewcontroller) , stats tint color still whitecolor(on uidocumentpickerviewcontroller), click picker cancel, view controller changed black color, not white color.

have known how change color when click alert action , pick stats bar tint color changed(changed black color), , dismiss picker , view controller still white color @ status bar tint color.

thank much.

have tried changing uinavigationbar's titletextattributes?

uinavigationbar.appearance().titletextattributes = [nsforegroundcolorattributename: uicolor.black]