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Flutter：RenderBox 没有布局

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我正在尝试创建一个 ListView，但是当我导入 list_form.dart
类时出现此错误。也许我在布局上犯了一些错误，因为如果我尝试在主文件中运行它，我不会收到这个错误。

这是错误：

    I/flutter (12956): 鈺愨晲鈺� EXCEPTION CAUGHT BY RENDERING LIBRARY 鈺炩晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲
I/flutter (12956): The following assertion was thrown during performResize():
I/flutter (12956): Vertical viewport was given unbounded height.
I/flutter (12956): Viewports expand in the scrolling direction to fill their container.In this case, a vertical
I/flutter (12956): viewport was given an unlimited amount of vertical space in which to expand. This situation
I/flutter (12956): typically happens when a scrollable widget is nested inside another scrollable widget.
I/flutter (12956): If this widget is always nested in a scrollable widget there is no need to use a viewport because
I/flutter (12956): there will always be enough vertical space for the children. In this case, consider using a Column
I/flutter (12956): instead. Otherwise, consider using the "shrinkWrap" property (or a ShrinkWrappingViewport) to size
I/flutter (12956): the height of the viewport to the sum of the heights of its children.
I/flutter (12956):
I/flutter (12956): When the exception was thrown, this was the stack:
I/flutter (12956): #0      RenderViewport.performResize.<anonymous closure> (package:flutter/src/rendering/viewport.dart:1133:15)
I/flutter (12956): #1      RenderViewport.performResize (package:flutter/src/rendering/viewport.dart:1186:6)
I/flutter (12956): #2      RenderObject.layout (package:flutter/src/rendering/object.dart:1616:9)
I/flutter (12956): #3      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #4      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #5      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #6      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #7      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #8      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #9      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #10     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #11     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #12     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #13     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #14     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #15     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #16     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #17     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #18     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #19     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:738:15)
I/flutter (12956): #20     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #21     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:738:15)
I/flutter (12956): #22     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #23     RenderPositionedBox.performLayout (package:flutter/src/rendering/shifted_box.dart:381:13)
I/flutter (12956): #24     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #25     MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:141:11)
I/flutter (12956): #26     _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:339:7)
I/flutter (12956): #27     MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:211:7)
I/flutter (12956): #28     RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:355:14)
I/flutter (12956): #29     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #30     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #31     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #32     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #33     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1192:11)
I/flutter (12956): #34     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #35     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #36     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #37     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #38     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1192:11)
I/flutter (12956): #39     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #40     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #41     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #42     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #43     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #44     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #45     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #46     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #47     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #48     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #49     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #50     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #51     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #52     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #53     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #54     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #55     RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:2884:13)
I/flutter (12956): #56     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #57     RenderStack.performLayout (package:flutter/src/rendering/stack.dart:520:15)
I/flutter (12956): #58     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #59     __RenderTheatre&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #60     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #61     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #62     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #63     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #64     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #65     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #66     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #67     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #68     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #69     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #70     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #71     RenderView.performLayout (package:flutter/src/rendering/view.dart:147:13)
I/flutter (12956): #72     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1506:7)
I/flutter (12956): #73     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:765:18)
I/flutter (12956): #74     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:270:19)
I/flutter (12956): #75     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:674:13)
I/flutter (12956): #76     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter (12956): #77     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (12956): #78     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (12956): #79     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:751:7)
I/flutter (12956): #81     _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
I/flutter (12956): #82     _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
I/flutter (12956): #83     _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:171:12)
I/flutter (12956): (elided one frame from package dart:async)
I/flutter (12956):
I/flutter (12956): The following RenderObject was being processed when the exception was fired:
I/flutter (12956):   RenderViewport#925a8 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956):   creator: Viewport 鈫� _ScrollableScope 鈫� IgnorePointer-[GlobalKey#8e8f7] 鈫� Semantics 鈫� Listener 鈫�
I/flutter (12956):   _GestureSemantics 鈫� RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#67ae5] 鈫�
I/flutter (12956):   _ScrollSemantics-[GlobalKey#17eb8] 鈫� RepaintBoundary 鈫� CustomPaint 鈫� RepaintBoundary 鈫�
I/flutter (12956):   NotificationListener<ScrollNotification> 鈫� 鈰�
I/flutter (12956):   parentData: <none> (can use size)
I/flutter (12956):   constraints: BoxConstraints(unconstrained)
I/flutter (12956):   size: MISSING
I/flutter (12956):   axisDirection: down
I/flutter (12956):   crossAxisDirection: right
I/flutter (12956):   offset: ScrollPositionWithSingleContext#c4917(offset: 0.0, range: null..null, viewport: null,
I/flutter (12956):   ScrollableState, AlwaysScrollableScrollPhysics -> ClampingScrollPhysics, IdleScrollActivity#2fecf,
I/flutter (12956):   ScrollDirection.idle)
I/flutter (12956):   anchor: 0.0
I/flutter (12956): This RenderObject had the following descendants (showing up to depth 5):
I/flutter (12956):   RenderSliverPadding#74d62 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956):     RenderSliverList#5c56d NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956): 鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲鈺愨晲
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderViewport#925a8 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderViewport#925a8 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#8bbda relayoutBoundary=up11 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#209b4 relayoutBoundary=up10 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderPointerListener#a9641 relayoutBoundary=up9 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#9f5b4 relayoutBoundary=up8 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#47944 relayoutBoundary=up7 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#e17a8 relayoutBoundary=up6 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#a2328 relayoutBoundary=up5 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#02607 relayoutBoundary=up4 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderFlex#79164 relayoutBoundary=up3 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: 'package:flutter/src/rendering/shifted_box.dart': Failed assertion: line 310 pos 12: 'child.hasSize': is not true.
I/flutter (12956): Another exception was thrown: NoSuchMethodError: The method '<=' was called on null.

这是 list_form.dart 类：

import 'package:flutter/material.dart';

class ListForm extends StatefulWidget {
  @override
  ListFormState createState() => new ListFormState();
}

class ListFormState extends State<ListForm> {
    List<String> products = ["Test1", "Test2", "Test3"];
    @override
    Widget build(BuildContext context) {
      return new Container(
        child: new Center(
          child: new Column(
            children: <Widget>[
              new Row(
                children: <Widget>[
                  new ListView.builder(
                    itemCount: products.length,
                    itemBuilder: (BuildContext ctxt, int index) {
                      return new Text(products[index]);
                    }
                  ),
                  new IconButton(
                    icon: Icon(Icons.remove_circle),
                    onPressed: () { },
                  )
                ],
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
              ),
              new TextField(
                decoration: new InputDecoration(
                  hintText: "Prodotto"
                ),
                onSubmitted: (String str) {
                  setState(() {
                    products.add(str);
                  });
                },
              ),
            ]
          )
        )
      );
    }
}

这是 app_base.dart 类：

import 'package:flutter/material.dart';
import '../UI/list_form.dart';

class AppBase extends StatefulWidget {
  @override
  State createState() => new AppBaseState();
}

class AppBaseState extends State<AppBase> {
  bool _pressed = true;

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.greenAccent,
      child: new Scaffold(
        body:
          new ListForm(),
        appBar: AppBar(
          centerTitle: true,
          title: const Text('Skeeper'),
          backgroundColor: Colors.green,
        ),
        floatingActionButton: FloatingActionButton(
          tooltip: 'Test',
          child: new Icon(Icons.add),
          backgroundColor: Colors.green,
          onPressed: () {
              setState(() {
                _pressed = !_pressed;
              });
          },
        ),
      )
    );
  }
}

如果有一些未使用的代码，请不要担心，这是一项正在进行的工作，这个错误只是阻止我继续我正在做的事情。


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2022-07-14

共1个答案

小编典典

问题是您将ListView内部放置在列/行中。异常中的文本很好地解释了错误。

为避免错误，您需要为ListView内部提供尺寸。

我建议你使用这个代码Expanded来通知水平尺寸（最大可用）和SizedBox（可能是一个容器）height:

    new Row(
      children: <Widget>[
        Expanded(
          child: SizedBox(
            height: 200.0,
            child: new ListView.builder(
              scrollDirection: Axis.horizontal,
              itemCount: products.length,
              itemBuilder: (BuildContext ctxt, int index) {
                return new Text(products[index]);
              },
            ),
          ),
        ),
        new IconButton(
          icon: Icon(Icons.remove_circle),
          onPressed: () {},
        ),
      ],
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
    )

,

2022-07-14