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大家好，我正在尝试构建一个可重用的 SliverList，我只是将 sliver 小部件作为列表传递到其中以显示，并加倍用于填充，但目前出现此错误

我正在尝试构建的可重用小部件的代码

class ScrollScreen extends StatelessWidget {
  ScrollScreen({
    @required this.pageTitle,
    @required this.pageImage,
    @required this.widgets,
    this.color = Colors.white,
  });

  final String pageTitle;
  final String pageImage;
  final List<Widget> widgets;
  final Color color;

  @override
Widget build(BuildContext context) {
return CustomScrollView(physics: const BouncingScrollPhysics(), slivers: [
  SliverBar(title: pageTitle, image: pageImage),
  SliverListLayout(widgets: widgets),
]);

}

SliverListLayout 类

class SliverListLayout extends StatelessWidget {
final double paddingTB;
final double paddingLR;
final List<Widget> widgets;
SliverListLayout({
@required this.widgets,
this.paddingTB,
this.paddingLR,
});

@override
Widget build(BuildContext context) {
return SliverList(
  delegate: SliverChildListDelegate([
    ...addPadding(widgets, paddingTB, paddingLR), //add padding wraps widgets in a padding widget and returns them,, not the issue works fine elsewhere
  ]),
);
}

} 堆栈跟踪：

The following NoSuchMethodError was thrown building             
NotificationListener<KeepAliveNotification>:
The method '>=' was called on null.
Receiver: null
Tried calling: >=(0.0)

The relevant error-causing widget was
SliverList
lib\…\custom_widgets\sliverlist_layout.dart:15
When the exception was thrown, this was the stack
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1      EdgeInsetsGeometry.isNonNegative
package:flutter/…/painting/edge_insets.dart:52
#2      new RenderPadding
package:flutter/…/rendering/shifted_box.dart:107
#3      Padding.createRenderObject
package:flutter/…/widgets/basic.dart:1652
#4      RenderObjectElement.mount

颤振医生：

PS C:\Users\Usuario\Desktop\AppName> flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 1.22.5, on Microsoft Windows [Versión 10.0.19042.746], locale es-ES)
 
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    ! Some Android licenses not accepted.  To resolve this, run: flutter doctor --android-licenses
[!] Android Studio (version 4.1.0)
    X Flutter plugin not installed; this adds Flutter specific functionality.
    X Dart plugin not installed; this adds Dart specific functionality.      
[√] VS Code (version 1.52.1)
[√] Connected device (1 available)

! Doctor found issues in 2 categories.
PS C:\Users\Usuario\Desktop\AppName>

添加填充

List<Widget> addPadding(List<Widget> widgets,
    [double paddingTB = 25.0, double paddingLR = 25.0]) {
  for (int i = 0; i < widgets.length; i++) {
    widgets[i] = Padding(
      padding: EdgeInsets.fromLTRB(
        paddingLR,
        paddingTB,
        paddingLR,
        paddingTB,
      ),
      child: widgets[i],
    );
  }
  return widgets;
}

我粘贴了 SliverListLayout 类中的代码（没有两个额外的参数），一切正常。SliverBar 还返回一个 SliverAppBar，它工作正常。非常感谢任何帮助。

4

1 回答 1

0

我不确定如何重现您的问题。我会推荐：

  1. 发布一个完整但最小的代码示例来重现您的问题
  2. 发布完整的控制台错误堆栈跟踪
  3. 提供有关您的配置的更多信息（颤振医生）

这是一个小代码示例，它做一些简单的事情，类似于（我认为）你试图实现的目标。

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      home: Scaffold(
          body: ReusableSliverList(
        title: 'Testing my ReusableSliverList',
        widgetPadding: EdgeInsets.symmetric(horizontal: 32.0, vertical: 16.0),
        widgets: List.generate(10, (index) => Text('Widget $index')).toList(),
      )),
    ),
  );
}

class ReusableSliverList extends StatelessWidget {
  final String title;
  final List<Widget> widgets;
  final EdgeInsets widgetPadding;

  const ReusableSliverList({
    Key key,
    this.title,
    this.widgets,
    this.widgetPadding,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return CustomScrollView(
      physics: const BouncingScrollPhysics(),
      slivers: [
        SliverAppBar(title: Text(title)),
        SliverList(
          delegate: SliverChildListDelegate(
            widgets
                .map((widget) => Padding(padding: widgetPadding, child: widget))
                .toList(),
          ),
        ),
      ],
    );
  }
}

基于您的问题编辑的完整工作代码（使用 addPadding）：

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      title: 'Flutter Demo',
      home: Scaffold(
        body: ScrollScreen(
          widgets: List.generate(10, (index) => Text('Widget $index')),
        ),
      ),
    ),
  );
}

class ScrollScreen extends StatelessWidget {
  ScrollScreen({
    // @required this.pageTitle,
    // @required this.pageImage,
    @required this.widgets,
    this.color = Colors.white,
  });

  // final String pageTitle;
  // final String pageImage;
  final List<Widget> widgets;
  final Color color;

  @override
  Widget build(BuildContext context) {
    return CustomScrollView(physics: const BouncingScrollPhysics(), slivers: [
//      SliverBar(title: pageTitle, image: pageImage),
      SliverListLayout(
        widgets: widgets,
        paddingLR: 16.0,
        paddingTB: 32.0,
      ),
    ]);
  }
}

class SliverListLayout extends StatelessWidget {
  final double paddingTB;
  final double paddingLR;
  final List<Widget> widgets;
  SliverListLayout({
    @required this.widgets,
    this.paddingTB,
    this.paddingLR,
  });

  @override
  Widget build(BuildContext context) {
    return SliverList(
      delegate: SliverChildListDelegate([
        ...addPadding(
          widgets,
          paddingTB,
          paddingLR,
        ),
      ]),
    );
  }

  List<Widget> addPadding(List<Widget> widgets,
      [double paddingTB = 25.0, double paddingLR = 25.0]) {
    for (int i = 0; i < widgets.length; i++) {
      widgets[i] = Padding(
        padding: EdgeInsets.fromLTRB(
          paddingLR,
          paddingTB,
          paddingLR,
          paddingTB,
        ),
        child: widgets[i],
      );
    }
    return widgets;
  }
}
于 2021-01-29T22:47:53.027 回答