无法在初始化程序中访问实例成员“_showSelectImageDialog”

Question

无法在初始化程序中访问实例成员“_showSelectImageDialog”。请帮我。提前致谢

 Step(
      isActive: false,
      state: StepState.editing,
      title: const Text('Account'),
      //subtitle: const Text("E"),
      content: Column(
        children: <Widget>[
        GestureDetector(
          onTap: _showSelectImageDialog,
           child: Container(
                  height: 150,
                  width: 150,
                  color: Colors.grey[200],
                  // ignore: unnecessary_null_comparison
                  child:  Icon(
                          Icons.person,
                          color: Colors.orangeAccent,
                          size: 150.0,
                        ),
                      // : Image(
                      //     image: FileImage(_image),
                      //     fit: BoxFit.contain,
                        ),
         ),