dart – 颤振垂直视口无界高度误差

概述我做了一个应用程序来显示一个州的医院列表. 这是Main.dart import 'package:flutter/material.dart';import 'package:url_launcher/url_launcher.dart';import 'dart:async' show Future;import 'package:flutter/services.dart' show 我做了一个应用程序来显示一个州的医院列表.

这是Main.dart

import 'package:Flutter/material.dart';import 'package:url_launcher/url_launcher.dart';import 'dart:async' show Future;import 'package:Flutter/services.dart' show rootBundle;import 'dart:convert';import 'package:emas_app/model/accounts_model.dart';Future<String> _loadAsset() async{  return await rootBundle.loadString('Assets/accounts.Json');}Future<Accounts> loadAccounts() async{  final response = await _loadAsset();  final JsonResponse = Json.decode(response);  Accounts accounts = new Accounts.fromJson(JsonResponse);  return accounts;}class ProvIDerList extends StatefulWidget {  @overrIDe  ListState createState() {    return new ListState();  }}class ListState extends State<ProvIDerList> {  @overrIDe  Widget build(BuildContext context) {    Widget newbody = new ExpansionTile(        Title: new Text("State name"),children: <Widget>[          new FutureBuilder<Accounts>(              future: loadAccounts(),builder: (context,snapshot){                if(snapshot.hasData){                return new ListVIEw.builder(                      itemCount: snapshot.data.accountinfo.length,itemBuilder: (context,index){                        String username = snapshot.data.accountinfo[index].name;                        String address = snapshot.data.accountinfo[index].street;                        String lat = snapshot.data.accountinfo[index].coordinates.lat;                        String lng = snapshot.data.accountinfo[index].coordinates.lng;                        return new ListTile(                            Title: new Text(username),trailing: new Row(                              mainAxisSize: MainAxisSize.min,mainAxisAlignment: MainAxisAlignment.end,children: <Widget>[                                new Iconbutton(                                    icon: Icon(Icons.info),onpressed: null                                ),new Iconbutton(                                    icon: Icon(Icons.directions),onpressed: null                                )                              ],)                        );                      });                }else{                  return new Center(                    child: new CircularProgressIndicator(),);                }              })    ]);    return new Scaffold(      appbar: new Appbar(Title: new Text("ProvIDers")),body: newbody    );  }}

这是显示扩展的ExpansionTile为空的输出：

这是错误抓住：

I/Flutter ( 6305): Vertical vIEwport was given unbounded height.I/Flutter ( 6305): VIEwports expand in the scrolling direction to fill their container.In this case,a verticalI/Flutter ( 6305): vIEwport was given an unlimited amount of vertical space in which to expand. This situationI/Flutter ( 6305): typically happens when a scrollable Widget is nested insIDe another scrollable Widget.

我已经尝试了我可以在Stack Overflow中找到的所有可能的解决方案,通过使用Expanded或Flexible包装ListVIEw.builder但它不起作用.关于如何解决这个问题的任何想法？

解决方法 有两种解决方案：

>使用ListVIEw的shrinkWrap属性

new ListVIEw.builder(        shrinkWrap: true,itemCount: ...

原因：

在您的情况下,ListVIEw位于ExpansionTile中. ExpansionTile将展示扩展并展示有多少孩子.当ListVIEw放置在ExpansionTile(无界约束小部件)中时,ListVIEw将扩展到scrollDirection中的最大大小.根据文档,

If the scroll vIEw does not shrink wrap,then the scroll vIEw will expandto the maximum allowed size in the [scrollDirection]. If the scroll vIEwhas unbounded constraints in the [scrollDirection],then [shrinkWrap] mustbe true.

>使用SizedBox为ListVIEw提供固定高度.

SizedBox(height: 200.0,child: new ListVIEw.builder(...))

总结

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