Question

我试图将水平滚动列表（ListTile）嵌入ExpansionTile中，并且收到很多错误。

flutter: The following RenderObject was being processed when the     exception was fired: RenderFlex#29789 relayoutBoundary=up25 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE:
flutter:   creator: Column ← Align ← ClipRect ← Column ← Padding ←   DecoratedBox ← Container ← AnimatedBuilder ←
flutter:     ExpansionTile ← Semantics ← DefaultTextStyle ← AnimatedDefaultTextStyle ← ⋯
flutter:   parentData: offset=Offset(0.0, 0.0) (can use size)
flutter:   constraints: BoxConstraints(0.0<=w<=361.0, 0.0<=h<=Infinity)
flutter:   size: MISSING
flutter:   direction: vertical
flutter:   mainAxisAlignment: start
flutter:   mainAxisSize: max
flutter:   crossAxisAlignment: center
flutter:   verticalDirection: down
flutter: This RenderObject had the following descendants (showing up to depth 5):
flutter:     child 1: _RenderScrollSemantics#7f6ab NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
flutter:       child: RenderPointerListener#71a85 NEEDS-LAYOUT

代码如下：

return SafeArea(
  child: Scaffold(key: myGlobals.scaffoldKey,
    backgroundColor: Colors.amberAccent,
    drawer:  drawer(),
    body:

    Padding(
      padding: const EdgeInsets.symmetric(horizontal: 1, vertical: 5),
      child: ListView.builder(
        scrollDirection: Axis.vertical,
        addRepaintBoundaries: true,
        reverse: false,
        shrinkWrap: true,
        addAutomaticKeepAlives: true,
        itemCount: mylist.length,
        itemBuilder: (context, counter)
        {


          return ExpansionTile(
                trailing: Text('test'),
                leading: Image.asset('test'),),
                title:   Text('Title'),
                children: [
                  Flexible(
                    //direction: Axis.horizontal,
                   // direction: Axis.vertical,
                   // verticalDirection: ,
                   // children: <Widget>[
                    child:
                      ListView.builder
                        (shrinkWrap: true,
                        itemCount: supplementsList.length,
                       // scrollDirection: Axis.horizontal,
                        itemBuilder: (BuildContext context, counter)
                        {
                          return Expanded(child: Text('hello'),);
                      } // itemBuilder
                    ),



                  ),
                ],

              ),
            ),
          );
        }, //itemBuilder
      ),
    ),

好吧，我试图将ListView.builder包装在Expanded小部件中。那没有做太多，所以我尝试了Flex和Flexible。他们什么也没做。我进行了冥想，并且我真的在努力向此文本框添加说明，因为在我进行详细说明之前不允许发布。

Answer 1

使用Container将内部listview.builder包裹起来并指定高度

Container(
           height : 300,
             child: ListView.builder(
                   shrinkWrap: true,
                   scrollDirection: Axis.horizontal,

完整代码

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(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  List<String> litems = ['1', '2', '3', '4'];
  List<String> litems1 = [' hi ', ' this ', ' is ', ' long ', ' long ',' long ',' long ',' long ',' long ',' long ',' long ',' long ',' long ',' long ',' long '];

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(
              child: ListView.builder(
                  shrinkWrap: true,
                  itemCount: litems.length,
                  itemBuilder: (BuildContext ctxt, int Index) {
                    return ExpansionTile(
                      title: Text(litems[Index]),
                      children: <Widget>[
                        Text(litems[Index]),
                        Container(
                          height : 300,
                          child: ListView.builder(
                              shrinkWrap: true,
                              scrollDirection: Axis.horizontal,
                              itemCount: litems1.length,
                              itemBuilder: (BuildContext ctxt, int Index) {
                                return Text(litems1[Index]);
                              }),
                        )
                      ],
                    );
                  }),
            ),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

使用ExpansionTile时出现布局错误

1 个答案: