InApp Purchases

Open Project in Xcode

And in Build & signin Enable InApp Purchase Option from capability.

Now Use Predefine InAppPurchase Page

InAppPurchaseScreen(
    appBarWidget: yourAppBarWidget(),
    onChildRender: (productDetails, previosPurchase) {
       return yourTileUI();
    },
    productIds: [], // Your Plan List
    onPurchaseCompleted: () {
        Navigator.pop(context);
    },
    onAuth: () {
     // Show your Login Ui
    },
 )