Flutter：如何修复“像素溢出的 RenderFlex”错误？

Question

我在我的Flutter 应用程序中使用GridView 来显示图像及其标题。请检查以下代码。

import 'package:flutter/material.dart';

import '../common_ui/search_bar.dart';

class PurchaseProductsPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return PurchaseProductsUI();
  }
}

class PurchaseProductsUI extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _PurchaseProductUIState();
  }
}

class _PurchaseProductUIState extends State<PurchaseProductsUI> {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return ListView(
      children: <Widget>[
        Container(
          margin: EdgeInsets.all(20),
          child: SearchBar(),
        ),
        Container(
            margin: EdgeInsets.all(20),
            child: GridView.builder(
                physics: ScrollPhysics(), // to disable GridView's scrolling
                shrinkWrap: true,
                itemCount: 20,
                gridDelegate: new SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 2),
                itemBuilder: (BuildContext context, int index) {
                  return Container(
                      padding: EdgeInsets.all(5), child: _buildImageBoxes());
                })),
      ],
    );
  }

  Widget _buildImageBoxes() {
    return 
   Column(
      children: <Widget>[
        Container(
          child: Image.network("https://picsum.photos/200/300/?random"),
        ),
        Container(
          padding: EdgeInsets.all(10),
          child:  Text("Text"),        )
      ],
    );

  }
}

运行上述代码时出现以下错误和 UI

I/flutter ( 2743): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 2743): The following message was thrown during layout:
I/flutter ( 2743): A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): The overflowing RenderFlex has an orientation of Axis.vertical.
I/flutter ( 2743): The edge of the RenderFlex that is overflowing has been marked in the rendering with a yellow and
I/flutter ( 2743): black striped pattern. This is usually caused by the contents being too big for the RenderFlex.
I/flutter ( 2743): Consider applying a flex factor (e.g. using an Expanded widget) to force the children of the
I/flutter ( 2743): RenderFlex to fit within the available space instead of being sized to their natural size.
I/flutter ( 2743): This is considered an error condition because it indicates that there is content that cannot be
I/flutter ( 2743): seen. If the content is legitimately bigger than the available space, consider clipping it with a
I/flutter ( 2743): ClipRect widget before putting it in the flex, or using a scrollable container rather than a Flex,
I/flutter ( 2743): like a ListView.
I/flutter ( 2743): The specific RenderFlex in question is:
I/flutter ( 2743):   RenderFlex#4a1bb OVERFLOWING
I/flutter ( 2743):   creator: Column ← Padding ← Container ← RepaintBoundary-[<14>] ← IndexedSemantics ←
I/flutter ( 2743):   NotificationListener<KeepAliveNotification> ← KeepAlive ← AutomaticKeepAlive ← SliverGrid ←
I/flutter ( 2743):   MediaQuery ← SliverPadding ← ShrinkWrappingViewport ← ⋯
I/flutter ( 2743):   parentData: offset=Offset(5.0, 5.0) (can use size)
I/flutter ( 2743):   constraints: BoxConstraints(w=150.0, h=150.0)
I/flutter ( 2743):   size: Size(150.0, 150.0)
I/flutter ( 2743):   direction: vertical
I/flutter ( 2743):   mainAxisAlignment: start
I/flutter ( 2743):   mainAxisSize: max
I/flutter ( 2743):   crossAxisAlignment: center
I/flutter ( 2743):   verticalDirection: down
I/flutter ( 2743): ◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤◢◤
I/flutter ( 2743): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
I/flutter ( 2743): Another exception was thrown: A RenderFlex overflowed by 111 pixels on the bottom.
Reloaded 0 of 446 libraries in 1,179ms.

下面是用户界面

我该如何解决这个问题？

Answer 1

尝试在 _buildImageBoxes() 函数中使用 Expanded 而不是 Container

  Widget _buildImageBoxes() {
    return Column(
      children: <Widget>[
        Expanded(
          child: Image.network("https://picsum.photos/500/500/?random"),
        ),
        Container(
          padding: EdgeInsets.all(10),
          child: Text("Text"),
        )
      ],
    );
  }

Answer 2

Expanded → 计算空间

Column 或Row 中的Expanded 或Flexible 小部件将使Flutter 计算剩余空间并将该空间用于布局。

不在Expanded 或Flexible 中的小部件的布局无论屏幕/约束空间如何。

---

为什么/如何工作

Column 和Row 分为两个主要阶段：

1. 非Flexible 项
2. Flexible 项目（Expanded 和 Flexible 小部件）

第一阶段

Flutter 执行第 1 阶段时没有考虑屏幕大小或任何其他限制。

Flutter 只是将所有非弹性因子的项目大小相加。

对于屏幕或其他限制而言，总和太大？ → RenderFlex overflowed 异常。

第二阶段

带有flex 构造函数参数的小部件是弹性因子项目。

即Flexible 或 Expanded 小部件。 （Spacer 也是，但没有人使用它。）

在第 1 阶段之后，所有 flex-factor 小部件的布局考虑到剩余空间。

---

非弹性布局阶段和弹性因子布局阶段之间的主要区别：

• 非弹性布局 → 不管空间
• 弹性因子布局→使用剩余空间

---

在Column 或Row 中，将小部件包装在Expanded 或Flexible 中，Flutter 将计算其布局的剩余空间。这将防止问题中出现RenderFlex overflowed 异常，因为每个Image 小部件都会根据空间限制自行调整大小。

但在第 1 阶段，没有空间限制。所以Images 不会调整大小（和溢出）。

Column 或 Row 中的子小部件 不 包裹在 Expanded 或 Flexible 中，无论屏幕/约束空间如何，都将以其固有尺寸布局。

之前

Space 400
  Column
    Image 150
    Image 150
    Image 150

非弹性图像总和：450。可用空间：400 → Overflowed

解决方案：使用阶段 2 → 使用计算空间

之后

在弹性小部件Expanded 中包装Image，可用高度计算 然后在Expanded（作为约束）和Image 之间共享 调整大小以适应在Expanded 约束内：

Space 400
  Column
    Expanded 133
      → Image ←
    Expanded 133
      → Image ←
    Expanded 133
      → Image ←

扩展的总和：399。空间：400 → OK

Answer 3

Widget build(BuildContext context) {

    final _screenSize = MediaQuery.of(context).size;

    return Container(
      height: _screenSize.height * 0.2,);
}                                                                                     

MediaQuery.of(context)它对我有用！

Answer 4

错误（因为键盘）：

您也可以在使用TextField 启动屏幕键盘时遇到此错误，以解决它

Scaffold(
  resizeToAvoidBottomInset: false, // <-- Set it to false.
  body: SingleChildScrollView(
    child: Column(
      children: [
        SizedBox(height: 600),
        TextField(),
      ],
    ),
  ),
)

错误（无键盘）：

在列/行中为您的孩子使用Expanded/Flexible。

• 使用Expanded：

  Column(
    children: [
      Expanded(
        flex: 1,
        child: Widget1(),
      ),
      Expanded(
        flex: 2,
        child: Widget2(),
      )
    ],
  )
  

• 使用Flexible：

  Row(
    children: [
      Flexible(
        flex: 1,
        child: Widget1(),
      ),
      Flexible(
        flex: 2,
        child: Widget2(),
      )
    ],
  )
  

• 给定一个固定的高度：

  Column(
    children: [
      SizedBox(
        height: 200,
        child: Widget1(),
      ),
      Expanded(
        flex: 2,
        child: Widget2(),
      )
    ],
  )
  

Answer 5

在您的Image.network 方法中使用fit 属性来减小图像的大小，因为它们更大并且从您的容器中溢出，或者您可以通过它们的height 和width 属性来放大您的Containers .