Flutter 类型“List<Future<Widget>>”不是“List<Widget>”类型的子类型

Question

我收到此错误： type 'List>' 不是 type 'List' 的子类型

这是触发错误的代码。

@override
  Widget build(BuildContext context) {
    if (widget.productId != null) {
      return StreamBuilder(
          stream:
              Document<Product>(path: 'app-data-inventory/${widget.productId}')
                  .streamData(),
          builder: (BuildContext context, AsyncSnapshot snap) {
            if (snap.hasError) {
              print(snap.error);
            }
            if (snap.hasData) {
              Product product = snap.data;

              return Scaffold(
                resizeToAvoidBottomPadding: false,
                backgroundColor: AppAppTheme.white,
                appBar: appBarComponents,
                key: _scaffoldKey,
                body: Stack(
                  children: <Widget>[
                       Builder(
                            builder: (context) => SingleChildScrollView(
                              child: Column(
                                  crossAxisAlignment:
                                      CrossAxisAlignment.stretch,
                                  mainAxisSize: MainAxisSize.min,
                                  children: [
                                    Container(
                                      color: AppAppTheme.primary,
                                      height: 230,
                                      child: _yourWidget(context, product.productStorage['paths']),
                                    ),
                                    SizedBox(
                                      height: 10,
                                    ),
                                    CheckboxListTile(
                                        title: const Text('Terms of services'),
                                        value: _product.termsAgreed != null
                                            ? _product.termsAgreed
                                            : false,
                                        onChanged: (val) {
                                          setState(
                                              () => _product.termsAgreed = val);
                                        }),
                                    SwitchListTile(
                                        title: const Text('Save as draft'),
                                        value: _product.productStatus == 'draft'
                                            ? true
                                            : false,
                                        onChanged: (bool val) => setState(() {
                                              _product.productStatus =
                                                  val ? 'draft' : 'unapproved';
                                            })),
                                  ]),
                            ),
                          )

                    ),
                  ],
                ),
                  ),
                ),
              );
            } else {
              return UIErrorsMessages.notFoundComponent(
                  context, 'Product not found!');
            }
          });
    } else {
      return UIErrorsMessages.somethingIsNotRightComponent(
          context, 'Something went wrong. Try again!');
    }
  }
}

我该如何解决这个问题？

Answer 1

您应该首先使用FutureBuilder 获取数据，然后将数据提供给您的小部件。

以下代码应该适合你：

（我没有完整的代码所以我没有测试过，如有任何问题请评论）

Widget _yourWidget(BuildContext context) {
    return 
          color: AppTheme.primary,
          height: 230,
          child: Wrap(
            children: 
            paths.map<Widget>((url) {
              return FutureBuilder(builder: (BuildContext context, AsyncSnapshot snapshot) {
                if (snapshot.hasData){
                  file = snapshot.data;
                  print(file);
                  return Column(
                    children: <Widget>[
                      FlatButton(
                        child: Text(
                          'Delete',
                          style: AppTheme
                              .titleWhite,
                        ),
                        onPressed: () {
                          print(url);
                        },
                      ),
                      Container(
                        width: 100.0,
                        height: 100.0,
                        margin:
                            EdgeInsets
                                .all(
                                    10),
                        color:
                            AppTheme
                                .warn,
                        child: ExtendedImage
                            .network(file ==
                                    null
                                ? '/assets/icons/icon-120x120.png'
                                : file),
                      )
                    ],
                  );
                }else{
                  return Center(child: CircularProgressIndicator());
                }
              },);
       });
  }

  Future fetchDownloadURL(){
    return await _storage
               .ref()
             .child(url)
             .getDownloadURL();
  }