Unhandled Exception: type 'Null' is not a subtype of type 'PageController' in ty-CodePudding

                  onPressed: () async {
                    if (pageController != null) {
                      if (pageController.page != 3) {
                        pageController = await pageController.nextPage(
                            duration: Duration(milliseconds: 300),
                            curve: Curves.easeOut) as PageController;
                      }
                    } else {
                      Navigator.of(context).pushNamed(WelcomeScreen.routeName);
                    }
                  },

Tried a lot to fix this but end up with nothing, if anyone could help. Thanks.

CodePudding user response：

You have a mistake here

pageController = await pageController.nextPage(
    duration: Duration(milliseconds: 300),
    curve: Curves.easeOut) as PageController;

The method pageController.nextPage does not return a PageController. In fact it returns nothing, it is a void method. And this is why the cast as PageController is failing. To put it simple: You cannot convert nothing (void) into something (PageController)

Therefore, you should replace the above line with just

await pageController.nextPage(
    duration: Duration(milliseconds: 300),
    curve: Curves.easeOut);