颤振：为什么在我的程序中无法识别颤振文档中的属性？

Question

when I'm working with flutter CupertinoScrollbar in flutter doc , I found the property thickness and thicknessWhileDragging . But when I want to try the two properties my program just couldn't identify them. It showed a red wavy line and said the named parameter isn't defined . So why this happens? The related code is below.

CupertinoScrollbar(
                          isAlwaysShown: true,
                          controller: sc,
                          thickness: 3, // it said the named parameter isn't defined
                          child: ListView.builder(
                            controller: sc,
                            itemCount: 1,
                            scrollDirection: Axis.vertical,
                            padding: EdgeInsets.fromLTRB(ScreenUtil.dp(22), 0, ScreenUtil.dp(23), ScreenUtil.dp(8.13)),
                            itemBuilder: (context, index) => Html(data: """$html""",),
                          ),
                        ),

Answer 1

Try flutter clean and then flutter pub get

if it still doesn't work, try close your code editor and then open it again