如何在Flutter的showModalBottomSheet上添加按钮（或其他Widget）？

Question

在左侧是设计。在我想要构建此设计的Flutter应用程序的右侧：

无论我尝试什么，我都不会把按钮放在行首。

我最后尝试过的是堆叠式小部件：

showModalBottomSheet(
  context: context,
  shape: RoundedRectangleBorder(
    ...
  ),
  builder: (BuildContext context) {
    return Stack(
      alignment: AlignmentDirectional.topCenter,
      children: <Widget>[
        Container(
          width: 50,
          height: 50,
          child: Image.asset('assets/images/add.png'),
          decoration: const BoxDecoration(
            gradient: LinearGradient(
              begin: Alignment.topLeft,
              end: Alignment.bottomRight,
              colors: <Color>[
                CustomColors.PurpleLight,
                CustomColors.PurpleDark,
              ],
            ),
            borderRadius: BorderRadius.all(
              Radius.circular(50.0),
            ),
            boxShadow: [
              BoxShadow(
                color: CustomColors.PurpleShadow,
                blurRadius: 10.0,
                spreadRadius: 5.0,
                offset: Offset(0.0, 0.0),
              ),
            ],
          ),
        ),
        Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            SizedBox(height: 50),
            Text('Add new task'),
            RaisedButton(
              onPressed: () {
                Navigator.pop(context);
              },
              textColor: Colors.white,
              padding: const EdgeInsets.all(0.0),
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(8.0),
              ),
              child: Container(),
            ),
            SizedBox(height: 20),
          ],
        ),
      ],
    );
  },
);

我希望您有一些建议或一个好的解决方案：）

Answer 1

不要使用showModalBottomSheet参数的形状，而是使showModalBottomSheet透明，然后将背景作为子项之一添加到堆栈中并更改其形状。然后您可以将按钮放在列中。

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: SafeArea(
          child: MyHomePage(),
        ),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  _onPressed() {
    showModalBottomSheet(
      backgroundColor: Colors.transparent,
      context: context,
      builder: (BuildContext context) {
        return Stack(
          alignment: Alignment.center,
          children: <Widget>[
            Positioned(
              top: MediaQuery.of(context).size.height / 2 - 100,
              child: Container(
                height: 200,
                width: MediaQuery.of(context).size.width,
                decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.vertical(top: Radius.elliptical(150, 30)),
                ),
              ),
            ),
            Positioned(
              bottom: 0,
              child: Column(
                children: <Widget>[
                  Container(
                    width: 50,
                    height: 50,
                    child: Image.asset('assets/images/add.png'),
                    decoration: const BoxDecoration(
                      gradient: LinearGradient(
                        begin: Alignment.topLeft,
                        end: Alignment.bottomRight,
                        colors: <Color>[
                          Colors.red,
                          Colors.blue,
                        ],
                      ),
                      borderRadius: BorderRadius.all(
                        Radius.circular(50.0),
                      ),
                      boxShadow: [
                        BoxShadow(
                          color: Colors.purple,
                          blurRadius: 10.0,
                          spreadRadius: 5.0,
                          offset: Offset(0.0, 0.0),
                        ),
                      ],
                    ),
                  ),
                  SizedBox(height: 50),
                  Text('Add new task'),
                  RaisedButton(
                    onPressed: () {
                      Navigator.pop(context);
                    },
                    textColor: Colors.white,
                    padding: const EdgeInsets.all(0.0),
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(8.0),
                    ),
                    child: Container(),
                  ),
                ],
              ),
            ),
          ],
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container(
        child: RaisedButton(
      onPressed: _onPressed,
    ));
  }
}