卡片重叠颤动中的凸起按钮

friends, I am thinking to make this type of view but I can't able to set the button overlapping like the given image I am using stack widget which is containing the text fields and the buttons as given image please check and help me out I also tried to use the center widgets as well but the view is coming as required in it also i had used the positioned widget but its getting button bottom of the screen like this but i need as the above image

我的布局设计

 class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    MyAppState myAppState() => new MyAppState();
    return myAppState();
  }
}

class MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(home: new Scaffold(body: new Builder(
      builder: (BuildContext context) {
        return new Stack(
          children: <Widget>[
            new Image.asset(
              'assets/images/bg.png',
              fit: BoxFit.cover,
            ),
            new Center(
              child: new Container(
                child: new Card(
                  color: Colors.white,
                  elevation: 6.0,
                  margin: EdgeInsets.only(right: 15.0, left: 15.0),
                  child: new Wrap(
                    children: <Widget>[
                      Center(
                        child: new Container(
                          margin: EdgeInsets.only(top: 20.0),
                          child: new Text(
                            'Login',
                            style: TextStyle(
                                fontSize: 25.0, color: secondarycolor),
                          ),
                        ),
                      ),
                      new ListTile(
                        leading: const Icon(Icons.person),
                        title: new TextFormField(
                          decoration: new InputDecoration(
                            hintText: 'Please enter email',
                            labelText: 'Enter Your Email address',
                          ),
                          keyboardType: TextInputType.emailAddress,
                        ),
                      ),
                      new ListTile(
                        leading: const Icon(Icons.lock),
                        title: new TextFormField(
                          decoration: new InputDecoration(
                            hintText: 'Please enter password',
                            labelText: 'Enter Your Password',
                          ),
                          keyboardType: TextInputType.emailAddress,
                          obscureText: true,
                        ),
                      ),
                      Container(
                        margin: EdgeInsets.only(top: 10.0, bottom: 15.0),
                        child: Center(
                          child: Text(
                            "FORGOT PASSWORD",
                            style: TextStyle(
                                decoration: TextDecoration.underline,
                                color: Colors.black,
                                fontSize: 16.0),
                          ),
                        ),
                      ),
                      Center(
                        child: Container(
                          margin: EdgeInsets.only(bottom: 40.0, top: 10.0),
                          child: Text.rich(
                            TextSpan(
                              children: const <TextSpan>[
                                TextSpan(
                                    text: 'NEW USER ? ',
                                    style: TextStyle(
                                        fontSize: 16.0, color: Colors.black)),
                                TextSpan(
                                    text: 'REGISTER',
                                    style: TextStyle(
                                        fontSize: 16.0,
                                        decoration: TextDecoration.underline,
                                        color: Colors.black)),
                              ],
                            ),
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
              ),
            ),
            new RaisedButton(
              onPressed: () {
                print('Login Pressed');
              },
              color: primarycolor,
              shape: new RoundedRectangleBorder(
                  borderRadius: new BorderRadius.circular(30.0)),
              child: new Text('Login',
                  style: new TextStyle(
                      color: Colors.white,
                      fontSize: 16.0,
                      fontWeight: FontWeight.bold)),
            ),
          ],
        );
      },
    )));
  }
}

这只是实现预期结果的众多方法之一。 在这种情况下，我假设您知道背景的高度。 同样，有很多方法可以实现您想要的目标。您的代码没有任何问题，您只需了解“事物”在 Flutter 中的工作原理即可

Widget demo = Stack(
  children: <Widget>[
    //First thing in the stack is the background
    //For the backgroud i create a column
    Column(
      children: <Widget>[
        //first element in the column is the white background (the Image.asset in your case)
        DecoratedBox(
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(20.0),
            color: Colors.white
          ),
          child: Container(
            width: 300.0,
            height: 400.0,
          )
        ),
        //second item in the column is a transparent space of 20
        Container(
          height: 20.0
        )
      ],
    ),
    //for the button i create another column
    Column(
      children:<Widget>[
        //first element in column is the transparent offset
        Container(
          height: 380.0
        ),
        Center(
          child: FlatButton(
            color: Colors.red,
            child: Text("Press Me"),
            onPressed: () {},
          ),
        )
      ]
    )
  ],
);