Flutter - DropdownMenuItem

问题描述

我正在尝试使用 DropdownButton 构建一个国家选择小部件，该小部件可以在任何地方使用，例如与其他小部件（例如标签）在 Row 中。但是当屏幕宽度太小时，我会出现渲染溢出错误。 Flutter 不能使用省略号或只是剪切文本。

以下代码最好在网络中进行测试。只需将浏览器变小即可查看问题。我尝试了 Flutter - DropdownButton overflow 的所有提示，但都没有奏效。

Flutter --version
Flutter 2.2.3 • channel stable • https://github.com/Flutter/Flutter.git
Framework • revision f4abaa0735 (4 weeks ago) • 2021-07-01 12:46:11 -0700
Engine • revision 241c87ad80
Tools • Dart 2.13.4

文件 main.dart 包含实例 var flag ，它应该代表一个标志图像，所以这个可以有一个固定的大小，但如果有，名字应该用省略号剪掉空间不足。

import 'package:Flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        primarySwatch: Colors.blue,),home: MyHomePage(),);
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<Country> countries = [
    Country('FR','France'),Country('GB','Great Britain'),Country('AG','Antigua and Barbuda Islands')
  ];
  String? flag = null;

  Widget _buildDropdown() {
    return DropdownButton<String>(
//      isExpanded: true,items: [
        for (Country country in countries)
          DropdownMenuItem(
            value: country.flag,child: Row(
              mainAxisAlignment: MainAxisAlignment.start,children: [
                SizedBox(
                  width: 30,child: Text(country.flag),//                Expanded( child:
//                Flexible( child:
                Text(
                  country.name,overflow: TextOverflow.ellipsis,//                ),],onChanged: (String? selectedFlag) => setState(() => flag = selectedFlag!),value: flag,);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Text overflow in Dropdown'),body: Container(
        width: 200,child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
              _buildDropdown(),Text('Selected $flag'),);}}

class Country {
  String flag;
  String name;
  Country(this.flag,this.name);
}

解决方法

我们试试

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        primarySwatch: Colors.blue,),home: MyHomePage(),);
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<Country> countries = [
    Country('FR','France'),Country('GB','Great Britain'),Country('AG','Antigua and Barbuda Islands Antigua and Barbuda IslandsAntigua and Barbuda Islands Antigua and Barbuda IslandsAntigua and Barbuda Islands,Antigua and Barbuda Islands')
  ];

  String flag = null;

  Widget _buildDropdown() {
    return DropdownButton<String>(
      isExpanded: true,items: [
        for (Country country in countries)
          DropdownMenuItem(
            value: country.flag,child: Wrap(
              children: [
                SizedBox(
                  width: 30,child: Text(country.flag),Container(
                  constraints: new BoxConstraints(
                    minHeight: 20.0,maxHeight: 20.0,child: Text(
                    country.name,],onChanged: (String selectedFlag) => setState(() => flag = selectedFlag),value: flag,);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Text overflow in Dropdown'),body: SingleChildScrollView(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
            _buildDropdown(),Text('Selected $flag'),);
  }
}

class Country {
  String flag;
  String name;

  Country(this.flag,this.name);
}

浏览器输出：