Question

我在下面分享小部件，我面临来自

的错误

 Expanded(
                  flex: 40,
                  child: ListView.builder(
                    shrinkWrap: true,
                    itemCount: items.length,
                    itemBuilder: (context, index) {
                      return Padding(
                        padding: EdgeInsets.all(2.0),
                        child: GestureDetector(
                          onTap: ()async{
                            if(_ingredients.length==0){
                              Ingredient ingredient= Ingredient(ingredientName:"${items[index]}",dropDownValue: "Çay Kaşığı",ingredientAmount: null);
                              categoryModels[widget.subCategoryId].subCategoryModels[widget.subCategoryCardId].ingredients.add(ingredient);
                              addIngredient(ingredient,context);
                              _toggleCardHeight();
                              _toggleCardSize();
                              setState(() {

                              });
                            }
                            else{
                              var flag=0;
                              for(var i in _ingredients){
                                if(i.ingredientName==items[index]){
                                  flag=-1;
                                  var response= await showAlertDialog(context);
                                  if (response==false){
                                    setState(() {});
                                    }
                                  }
                                }
                              if(flag==0){
                                Ingredient ingredient=Ingredient(ingredientName:"${items[index]}",dropDownValue: "Çay Kaşığı",ingredientAmount: null);
                                categoryModels[widget.subCategoryId].subCategoryModels[widget.subCategoryCardId].ingredients.add(ingredient);
                                addIngredient(ingredient,context);
                                setState(() {});
                                }
                              }
                            },
                          child: Container(
                            decoration: BoxDecoration(
                              borderRadius: BorderRadius.circular(90),
                              border: Border.all(style:BorderStyle.solid,width: 1),
                              color: Colors.white54,

                            ),
                            child: Padding(
                              padding: EdgeInsets.all(5),
                              child: Text('${items[index]}',style: TextStyle(fontWeight: FontWeight.bold),)),
                          ),
                        ),
                      );
                    },
                  ),
                ),

创建成分对象后，我尝试添加对象列表。这是对象模型的代码。


class CategoryModel{
  CategoryModel(
    {
      this.categoryId,
      this.categoryImagePath,
      this.categoryName,
      this.categoryColor,
      this.subCategory
    });
  final SubCategoryModel subCategory;
  final Color categoryColor;
  final List<SubCategoryModel> subCategoryModels=[SubCategoryModel()];
  int categoryId;
  String categoryImagePath;
  String categoryName;

}
class SubCategoryModel{
  SubCategoryModel(
    {
      this.subCategoryId,
      this.subCategoryImagePath,
      this.subCategoryName,
      this.categoryColor,
      this.recipeId,
      this.ingredients,
      this.recipePhotoDir,
      this.recipeTextFromSpeechProcessing,
      this.recordedVoiceDir});

  final Color categoryColor;
  final double recipeId;
  int subCategoryId;
  String subCategoryImagePath;
  String subCategoryName;
  List<Ingredient> ingredients=[];
  String recipeTextFromSpeechProcessing;
  String recipePhotoDir;
  String recordedVoiceDir;
}

错误

/AndroidAudioRecorder( 5385): handleHasPermission true
E/flutter ( 5385): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: NoSuchMethodError: The method 'add' was called on null.
E/flutter ( 5385): Receiver: null
E/flutter ( 5385): Tried calling: add(Instance of 'Ingredient')
E/flutter ( 5385): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
E/flutter ( 5385): #1      _AddIngredientsCardState.build.<anonymous closure>.<anonymous closure> (package:lezzet_kitabi/recipe_screen_cards.dart:382:124)
E/flutter ( 5385): #2      _AddIngredientsCardState.build.<anonymous closure>.<anonymous closure> (package:lezzet_kitabi/recipe_screen_cards.dart:379:34)
E/flutter ( 5385): #3      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
E/flutter ( 5385): #4      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:607:11)
E/flutter ( 5385): #5      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:296:5)
E/flutter ( 5385): #6      BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:267:7)
E/flutter ( 5385): #7      GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:157:27)
E/flutter ( 5385): #8      GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:443:20)
E/flutter ( 5385): #9      GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:419:22)
E/flutter ( 5385): #10     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:288:11)
E/flutter ( 5385): #11     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:374:7)
E/flutter ( 5385): #12     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:338:5)
E/flutter ( 5385): #13     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:296:7)
E/flutter ( 5385): #14     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:279:7)
E/flutter ( 5385): #15     _rootRunUnary (dart:async/zone.dart:1370:13)
E/flutter ( 5385): #16     _CustomZone.runUnary (dart:async/zone.dart:1265:19)
E/flutter ( 5385): #17     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1170:7)
E/flutter ( 5385): #18     _invoke1 (dart:ui/hooks.dart:186:10)
E/flutter ( 5385): #19     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:282:7)
E/flutter ( 5385): #20     _dispatchPointerDataPacket (dart:ui/hooks.dart:96:31)

请帮助我如何解决它？祝你今天过得愉快.............................................. ………………………………………………………………………………………………………………………………………………………… .....................................

Answer 1

这一行导致错误：

categoryModels[widget.subCategoryId].subCategoryModels[widget.subCategoryCardId].ingredients.add(ingredient);

因为 categoryModels[widget.subCategoryId].subCategoryModels[widget.subCategoryCardId].ingredients 是 null，您可以尝试先检查它是否为空，例如添加 ? :

categoryModels[widget.subCategoryId].subCategoryModels[widget.subCategoryCardId]?.ingredients

未处理的异常：NoSuchMethodError：在 null 上调用了方法“add”。？

错误

1 个答案: