dart 在构建时抛出了以下RangeError：RangeError(index)：无效值：有效值范围为空：0

3pvhb19x  于 2023-07-31  发布在  其他
关注(0)|答案(1)|浏览(112)

不知道问题出在哪里。请帮助我，因为我是新的Flutter
Widget代码：

Expanded(
        child: Container(
                      padding: EdgeInsets.symmetric(horizontal: 16),
                      child: ListView.builder(
                        itemBuilder: (context, index) {
                          print(sources);
                          print(articles);
                          return isSourceNews ?
                           SourceTile(
                            url: sources[index].url,
                            name: sources[index].name,
                            description: sources[index].description,
                          )
                              :
                          BlogTile(
                            imageUrl: articles[index].urlToImage,
                            title: articles[index].title,
                            description: articles[index].description,
                            url: articles[index].url,
                          ) ;
                        },
                        shrinkWrap: true,
                        physics: ClampingScrollPhysics(),
                        itemCount: articles.length,
                      ),
                    ),
                  )

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用于从API获取数据的Dart文件代码

class SourceNews {
  List<SourceModel> news = [];

  Future<void> getSourceNews() async {
    var url = Uri.parse(
        "https://newsapi.org/v2/sources?language=$language&apiKey=$API_KEY");
    var response = await http.get(url);
    var jsonData = jsonDecode(response.body);
    if (jsonData['status'] == 'ok') {

      for(var element in jsonData['sources']){
        if (element['url'] != null && element['description'] != null) {
          SourceModel sourceModel = SourceModel(
            name: element['name'],
            url: element['url'],
            description: element['description'],
          );
          if(sourceModel!=null) {
            news.add(sourceModel);
          }
        }
      }
      //
      // jsonData['sources'].forEach((element) {
      //   if (element['url'] != null && element['description'] != null) {
      //     SourceModel sourceModel = SourceModel(
      //       name: element['name'],
      //       description: element['description'],
      //       url: element['url'],
      //     );
      //     if(sourceModel!=null) {
      //       news.add(sourceModel);
      //     }
      //
      //   }
      // });
    }
  }
}

型
错误堆栈：

======== Exception caught by widgets library =======================================================
The following RangeError was thrown building:
RangeError (index): Invalid value: Not in inclusive range 0..2: 3

When the exception was thrown, this was the stack: 
#0      List.[] (dart:core-patch/growable_array.dart:264:36)
#1      _HomeState.dashboard.<anonymous closure> (package:news_app/views/home.dart:398:41)
#2      SliverChildBuilderDelegate.build (package:flutter/src/widgets/scroll_delegate.dart:489:22)
#3      SliverMultiBoxAdaptorElement._build (package:flutter/src/widgets/sliver.dart:828:28)
#4      SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:842:55)
#5      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2720:19)
#6      SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:834:12)
#7      RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:351:23)
#8      RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:2506:59)
#9      PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:1062:15)
#10     RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:2506:14)
#11     RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:340:5)
#12     RenderSliverMultiBoxAdaptor.insertAndLayoutChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:488:5)
#13     RenderSliverList.performLayout.advance (package:flutter/src/rendering/sliver_list.dart:241:19)
#14     RenderSliverList.performLayout (package:flutter/src/rendering/sliver_list.dart:283:12)
#15     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#16     RenderSliverEdgeInsetsPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:139:12)
#17     RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:361:11)
#18     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#19     RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:534:13)
#20     RenderShrinkWrappingViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1882:12)
#21     RenderShrinkWrappingViewport.performLayout (package:flutter/src/rendering/viewport.dart:1833:20)
#22     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#23     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#24     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#25     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#26     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#27     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#28     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#29     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#30     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#31     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#32     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#33     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#34     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#35     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#36     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#37     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#38     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#39     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#40     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#41     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#42     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#43     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#44     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#45     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#46     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1449:11)
#47     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#48     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#49     RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:238:12)
#50     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#51     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#52     ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:52:11)
#53     RenderFlex._computeSizes (package:flutter/src/rendering/flex.dart:868:45)
#54     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:903:32)
#55     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#56     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#57     RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:122:14)
#58     RenderObject.layout (package:flutter/src/rendering/object.dart:2395:7)
#59     RenderBox.layout (package:flutter/src/rendering/box.dart:2386:11)
#60     MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:171:12)
#61     _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:1056:7)
#62     MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:235:7)
#63     RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:403:14)
#64     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:2234:7)
#65     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1016:18)
#66     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:492:19)
#67     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:905:13)
#68     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:358:5)
#69     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1284:15)
#70     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1214:9)
#71     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1072:5)
#72     _invoke (dart:ui/hooks.dart:142:13)
#73     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:359:5)
#74     _drawFrame (dart:ui/hooks.dart:112:31)
====================================================================================================

型
尝试检查循环不会在空数据上运行或越界，但没有找到解决方案，API数据完全正常，我认为错误是在溢出语法中。

dart

1条答案

按热度按时间
8i9zcol2

8i9zcol21#

有两个对象列表来显示数据，但您仍然对源列表使用相同的itemCount。

itemCount: isSourceNews ? sources.length : articles.length,

字符串

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