Flutter 即使使用所有位置(positional)参数，定位小部件也不会滚动

我想让个人资料页面的一些信息可以滚动.对于布局，我使用堆栈作为父窗口小部件，并用定位窗口小部件填充它.我用所有位置参数填充了定位小部件，当我把它放在屏幕中间时，它允许我滚动它.似乎我越往下推小部件，滚动的区域就越小.直到这个区域消失.

最后一个定位的小部件是我想使其可滚动的小部件.我还把它和固定号码一起使用，但没用.

我是编程新手，所以我希望能把我的问题说清楚.提前谢谢你帮我.

这是我的代码:

    return Scaffold(
      appBar: AppBar(
        elevation: 2,
        leading: BackButton(onPressed: () {
          Navigator.pop(context,
              MaterialPageRoute(builder: (context) => eventHomeScreen()));
        }),
        backgroundColor: Colors.teal,
        title: Text('Leute', style: TextStyle(fontSize: 28)),
        actions: [
          IconButton(
            iconSize: 26,
            icon: Icon(Icons.chat),
            tooltip: 'Chat-Anfrage schicken',
            onPressed: () {
              Navigator.of(context).push(MaterialPageRoute(
                  builder: (context) => chatRequestSentScreen.withUser(user)));
            },
          )
        ],
      ),
      body: Stack(
        alignment: Alignment.bottomCenter,
        clipBehavior: Clip.none,
        children: <Widget>[
          Container(
            width: MediaQuery.of(context).size.width * 1,
            height: MediaQuery.of(context).size.height * .35,
            decoration: BoxDecoration(
              image: DecorationImage(
                image: user.getProfilePicture(),
                fit: BoxFit.cover,
              ),
            ),
          ),
          Positioned(
            bottom: -MediaQuery.of(context).size.height * 0.19,
            child: Card(
              color: Colors.teal.shade50,
              shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.only(
                topLeft: Radius.circular(40),
                topRight: Radius.circular(40),
              )),
              elevation: 0,
              child: Container(
                width: MediaQuery.of(context).size.width * 1,
                height: MediaQuery.of(context).size.height * 0.26,
                child: Column(
                  children: [
                    Text(
                      user.getFullName(),
                      style: TextStyle(
                        fontWeight: FontWeight.bold,
                        fontSize: 24,
                      ),
                    ),
                    Text(user.getCurrentAge().toString() + " Jahre",
                        style: TextStyle(
                          fontSize: 22,
                        )),
                    Text('Zuletzt aktiv: Heute',
                        style: TextStyle(
                          color: Colors.grey,
                          fontSize: 16,
                        )),
                    SizedBox(
                      height: 10,
                    ),
                    Container(
                      margin: EdgeInsets.symmetric(horizontal: 20),
                      padding:
                          EdgeInsets.symmetric(horizontal: 30, vertical: 5),
                      child: Text(user.getBio(),
                          maxLines: 3,
                          overflow: TextOverflow.ellipsis,
                          textAlign: TextAlign.center,
                          style: TextStyle(
                            fontSize: 20,
                          )),
                    ),
                    SizedBox(
                      height: 50,
                    ),
                  ],
                ),
              ),
            ),
          ),
          Positioned(
            top: MediaQuery.of(context).size.height * 0.45,
            left: 0.0,
            right: 0.0,
            bottom: -MediaQuery.of(context).size.height * 0.55,
            child: Container(
              decoration: BoxDecoration(
                  color: Colors.black87,
                  borderRadius: BorderRadius.only(
                    topLeft: Radius.circular(40),
                    topRight: Radius.circular(40),
                  )),
                width: MediaQuery.of(context).size.width * 1,
                height: MediaQuery.of(context).size.height * 0.4,
                child:
                Container(
                        margin: EdgeInsets.symmetric(horizontal: 20, vertical: 20),
                        padding:
                            EdgeInsets.symmetric(horizontal: 30, vertical: 5),
                        child: SingleChildScrollView(
                          physics: AlwaysScrollableScrollPhysics(),
                          child: Column(
                            children: SharedScreenFeatures.getSports(
                                user.getSports()),
                          ),
                        ),
                ),
              ),
            ),
        ],
      ),
    );
  }
}```