颤音：空检查操作员在零值错误上使用

Question

我正在研究一个简单的电子商务应用程序。我有以下错误的错误：

e/flutter（13586）：[错误：flutter/lib/ui/ui_dart_state.cc（209）]未手持的例外：null check Operator在Null值

can 上使用的null检查操作员't算出什么是什么原因导致了此错误，即使我看到了类似的情况并尝试在我的代码中处理null值：

all_products.dart：

...
Widget AllProducts() {
  ...
      WatchBoxBuilder(
  box: Hive.box<Product>('products'),
  builder: (context, box) {
    if (box != null) {
      return ListView.builder(
        padding: EdgeInsets.only(
            top: 10, left: 25, right: 25),
        itemCount: products.length,
        itemBuilder: (BuildContext context, int idx) {
          return Padding(
            padding: EdgeInsets.only(bottom: 10),
            child: buildProduct(idx),
          );
        },
      );
    } else return Container();
  },
  ),
  ],
  );
}
...
Widget buildProduct(int idx) {
  return Container(
    height: 250,
    decoration: BoxDecoration(
      color: Colors.deepPurple[600],
      borderRadius: BorderRadius.all(Radius.circular(30)),
      boxShadow: [BoxShadow(color: Colors.deepPurple, blurRadius: 7)],
    ),
  child: Row(
    mainAxisAlignment: MainAxisAlignment.start,
      textDirection: TextDirection.ltr,
      children: [
        Expanded(
  child: Container(
    padding: EdgeInsets.only(left: 10),
    child: Image.file(File(product(idx).image), width: 150, height: 150),
    alignment: Alignment.centerLeft,
        ),
        ),
    Expanded(
      child: Column(
children: [
Padding(
  padding: const EdgeInsets.only(top: 15, right: 10),
  child:   Container(
    height: 30,
    child:   Text(
      product(idx).name,
      style: GoogleFonts.lato(fontSize: 17.5, fontWeight: FontWeight.bold),
      textAlign: TextAlign.center,
    ),
  ),
),
    Padding(
      padding: const EdgeInsets.only(top: 10),
      child: Text(
  product(idx).description,
  style: GoogleFonts.lato(fontSize: 12.5, color: Colors.white),
        textAlign: TextAlign.left,
  ),
    ),
],
          ),
    ),
      ],
    ),
  );
}
...

product_details.dart：

...
final picker = ImagePicker();
final titleCtrl = TextEditingController();
final descriptionCtrl = TextEditingController();
final priceCtrl = TextEditingController();
String? image;

Widget ProductDetails() {
  ...
 TextField(
              decoration: InputDecoration(
                icon: Icon(Icons.title),
                labelText: 'Product\'s name',
              ),
              controller: titleCtrl,
            ),
          ),
      Padding(
        padding: const EdgeInsets.only(bottom: 15),
        child: TextField(
          decoration: InputDecoration(
            icon: Icon(Icons.article_outlined),
            labelText: 'Product\'s specifications',
            hintText: 'Describe the product...'
          ),
          maxLines: null,
          controller: descriptionCtrl,
        ),
          ),
    Padding(
      padding: const EdgeInsets.only(bottom: 15),
      child: TextField(
        decoration: InputDecoration(
          icon: Icon(Icons.attach_money),
          labelText: 'Product\'s price',
        ),
        keyboardType: TextInputType.number,
        controller: priceCtrl,
      ),
    ),
          Padding(
            padding: const EdgeInsets.only(bottom: 10),
            child: Container(
              height: 100,
              decoration: BoxDecoration(
                color: Colors.deepPurple[300],
                borderRadius: BorderRadius.all(Radius.circular(10)),
              ),
              child: image != null ? Image.file(File(image!)) :
              Center(child: Icon(Icons.image_outlined, size: 30)),
            ),
          ),
          Padding(
            padding: const EdgeInsets.only(bottom: 15),
            child: OutlinedButton(
               child: Text('Pick an image from gallery'),
              onPressed: () async {
                 image = await picker.pickImage(
                     source: ImageSource.gallery).toString();
              },
            ),
          ),
          ...
OutlinedButton(
                  child: Text('Save'),
                  onPressed: () {
                    Product product = Product(
                      name: titleCtrl.text != null ? titleCtrl.text : '',
                      description: descriptionCtrl.text != null ?
                      descriptionCtrl.text : '',
                      price: priceCtrl.text != null ? priceCtrl.text : '',
                      image: image != null ? image! : '',
                    );
                    addProduct(product);
                    Get.back();
                   },
  ),
  ),
            ],
          ),
        ],
      ),
    ),
  );
}
...

任何帮助：/

编辑：

stack Trace：

E/flutter ( 3030): #0      MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:121:86)
E/flutter ( 3030): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:146:36)
E/flutter ( 3030): #2      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:329:12)
E/flutter ( 3030): #3      MethodChannelPathProvider.getApplicationDocumentsPath (package:path_provider_platform_interface/src/method_channel_path_provider.dart:52:10)
E/flutter ( 3030): #4      getApplicationDocumentsDirectory (package:path_provider/path_provider.dart:115:40)
E/flutter ( 3030): #5      main (package:apple_estore/main.dart:8:30)
E/flutter ( 3030): #6      _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:145:25)
E/flutter ( 3030): #7      _rootRun (dart:async/zone.dart:1428:13)
E/flutter ( 3030): #8      _CustomZone.run (dart:async/zone.dart:1328:19)
E/flutter ( 3030): #9      _runZoned (dart:async/zone.dart:1863:10)
E/flutter ( 3030): #10     runZonedGuarded (dart:async/zone.dart:1851:12)
E/flutter ( 3030): #11     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:141:5)
E/flutter ( 3030): #12     _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
E/flutter ( 3030): #13     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
E/flutter ( 3030):

Answer 1

BuildProduct（IDX）中的问题。 ListViewBuilder无法从数据库中获取所有值（有些是空或空的）。因此，请一一评论列表项目并检查结果。有关更多信息，请提供BuildProduct（）代码。