swiftswiftuiuipageviewcontrolleruipagecontroluiviewrepresentable

How to update page indicator in SwiftUI?


Interface: SwiftUI
Life Cycle: SwiftUI
Language: Swift
Xcode version: 12.5

I want to use a page indicator in the custom carousel view with core data. The indicator works fine with the current code below, but if a page is added or deleted from Core Data, the number of indicators does not change.

When adding or deleting a page, pages.count is changed, but I checked that func makeUIView() is not executed again.

How can I reload the func makeUIView automatic, when the value of self.pages.count changed?

struct PageControl : UIViewRepresentable {
    @EnvironmentObject var ani: CarouselModel
    @FetchRequest(entity: Page.entity(),
                  sortDescriptors: [NSSortDescriptor(keyPath: \Page.name, ascending: true)]
    ) var pages: FetchedResults<Page>
    
    func makeUIView(context: Context) -> UIPageControl {
        let view = UIPageControl()
        view.currentPageIndicatorTintColor = UIColor(red: 100/255, green: 255/255, blue: 177/255, alpha: 1.0)
        view.pageIndicatorTintColor = UIColor(red: 100/255, green: 255/255, blue: 177/255, alpha: 1.0).withAlphaComponent(0.2)
        view.numberOfPages = self.pages.count + 1
        
        return view
    }
    
    func updateUIView(_ uiView: UIPageControl, context: Context) {
        // Updating Page Indicator When Ever Page Changes...
        DispatchQueue.main.async {
            uiView.currentPage = Int(self.ani.count)
        }
    }
}

Solution

  • I got it!

    Put the below line from func makeUIView to func updateUIView

    uiView.numberOfPages = pages.count + 1 
    

    Final

    func updateUIView(_ uiView: UIPageControl, context: Context) {
                // Updating Page Indicator When Ever Page Changes...
                DispatchQueue.main.async {
                    uiView.currentPage = Int(self.ani.count)
                    uiView.numberOfPages = pages.count + 1
                }
            }