为什么 showModalBottomSheet() 函数不起作用

Question

为什么此代码不起作用并且未显示底部工作表。我也试过运行代码，但它仍然不起作用。我想在单击按钮时在颤动中显示模态底部工作表。

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  void startInputAction(BuildContext context) {
    showModalBottomSheet(
      context: context,
      builder: (_) {
        return Container(
          height: 200,
          padding: EdgeInsets.all(10),
          child: Text("Something"),
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("Error Practice Bottom Sheet"),
          backgroundColor: Colors.purple,
        ),
        body: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              RaisedButton(
                color: Colors.purple,
                padding: EdgeInsets.all(20),
                child: Text("Click here"),
                onPressed: () => startInputAction(context),
              )
            ],
          ),
        ),
      ),
    );
  }
}

Answer 1

MateriaApp处于同一级别，这就是您收到此错误的原因。

以下代码将解决您的问题。

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
      home: MyApp(),
    ));

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  void startInputAction(BuildContext context) {
    showModalBottomSheet(
        context: context,
        builder: (_) {
          return Container(
            height: 200,
            padding: EdgeInsets.all(10),
            child: Text("Something"),
          );
        });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Error Practice Bottom Sheet"),
        backgroundColor: Colors.purple,
      ),
      body: SingleChildScrollView(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
                color: Colors.purple,
                padding: EdgeInsets.all(20),
                child: Text("Click here"),
                onPressed: () => startInputAction(context))
          ],
        ),
      ),
    );
  }
}