在最新版本的 flutter 上使用 Carousel 时，getter 'key' 被调用为 null

Question

将 flutter 更新到最新版本后，我在 Carousel 上遇到了这个异常。 Carousel 在 flutter 版本 1.22.4 上运行良好。但是在切换到最新版本 (2.0.3) 后，我遇到了这个异常。下面是代码和异常。我正在使用下面的包 https://pub.dev/packages/carousel_pro

异常

════════ Exception caught by rendering library ═════════════════════════════════ The following NoSuchMethodError was thrown during performLayout(): The getter 'key' was called on null. Receiver: null Tried calling: key

The relevant error-causing widget was Carousel lib\…\homeViews\homeAppBarDelegate.dart:39 When the exception was thrown, this was the stack #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5) #1 SliverChildListDelegate.build package:flutter/…/widgets/sliver.dart:722 #2 SliverMultiBoxAdaptorElement._build package:flutter/…/widgets/sliver.dart:1201 #3 SliverMultiBoxAdaptorElement.createChild. package:flutter/…/widgets/sliver.dart:1214 #4 BuildOwner.buildScope package:flutter/…/widgets/framework.dart:2647 ... The following RenderObject was being processed when the exception was fired: RenderSliverFillViewport#4a87d relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT RenderObject: RenderSliverFillViewport#4a87d relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT parentData: paintOffset=Offset(0.0, 0.0) (can use size) constraints: SliverConstraints(AxisDirection.right, GrowthDirection.forward, ScrollDirection.idle, scrollOffset: 0.0, remainingPaintExtent: 411.4, crossAxisExtent: 230.0, crossAxisDirection: AxisDirection.down, viewportMainAxisExtent: 411.4, remainingCacheExtent: 411.4, cacheOrigin: 0.0) geometry: null no children current live ════════════════════════════════════════════════════════════════════════════════

代码

class HomeView extends StatefulWidget {
  @override
  _HomeViewState createState() => _HomeViewState();
}

class _HomeViewState extends State<HomeView> {
  @override
Widget build(BuildContext context) {
return Scaffold(
      ...................
Stack(
    children: [
        CustomScrollView(
          controller: _scrollController,
          slivers: <Widget>[
           SliverPersistentHeader(
                delegate: HomeAppBarDelegate(
                    maxExtent: 230,
                    minExtent: 50,
                ),
                pinned: true,
                floating: false,
             ),
          ],
       ),
    ],
   ),
),    
},
}

import 'package:carousel_pro/carousel_pro.dart';

class HomeAppBarDelegate extends SliverPersistentHeaderDelegate {
  @override
  Widget build(
      BuildContext context, double shrinkOffset, bool overlapsContent) {

return Stack(
     children: [
      ...................

        // ------------------------------ C O V E R   B L U R   I M A G E S
        Carousel(
           animationCurve: Curves.easeInOutQuint,
           animationDuration: Duration(seconds: 1),
           dotBgColor: Colors.transparent,
           overlayShadow: true,
           autoplayDuration: Duration(seconds: 4),
           showIndicator: false,
           dotIncreasedColor: Colors.brown,
           onImageChange: (prevInd, currInd) => coverImgIndex = currInd,
           images: [
              ...coverImagesList.map(
                (singleImg) => HomeBlurCoverImg(
                 imgURl: singleImg,
                 animationVal: animationVal,
                 maxExtent: maxExtent,
                 sizingInformation: sizingInformation,
                      ),
                    ),
                  ],
                ),
              ],
            ),

出现黑屏

Answer 1

错误是 geometry: null no children current live。您的小部件未收到任何 children，您能否确认这不是问题所在？在运行小部件之前填充您的项目，或者在呈现它之前使用 isNotEmpty 检查，这应该可以解决您的问题。具体来说 coverImagesList，我看不到您将此列表的值传递到哪里，或者您的小部件树从哪里获取它。

在最新版本的 flutter 上使用 Carousel 时，getter 'key' 被调用为 null

The getter 'key' was called on null while using Carousel on latest version of flutter

package

carousel

dart

flutter