如何使用 flutter 从 firebase 中检索数据

Question

Hello I'm new to flutter and wanted to create a recipe app but I can't seem to be able to retrieve recipe data from firebase to my app.

This is the recipe model that I created.

import 'package:cloud_firestore/cloud_firestore.dart';
    
class RecipeModel {
  late String fid;
  late String name;
  late String category;
  late String imgUrl;
  late String duration;
  List ingredients = [];
  List preparation = [];

    
  RecipeModel.fromMap(Map<String, dynamic> data){
    fid = data['fid'];
    name = data['name']; 
    category = data['category'];
    duration = data['duration'];
    imgUrl = data['imgUrl'];
    ingredients = data['ingredients'];
    preparation = data['preparation'];
  }
}

I want to display all the recipes in this screen in list view. I tried different methods but it didn't work.

class AllRecipeScreen extends StatefulWidget {
  @override 
  _AllRecipeScreenState createState() => _AllRecipeScreenState();
}

class _AllRecipeScreenState extends State<AllRecipeScreen>{

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: ListView.separated(
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              leading: Image.asset(
                    ToolsUtilities.imageRecipe[index],
                    width: 120,
                fit: BoxFit.fitWidth,
              ),
              title: Text("Recipe Name"),
              subtitle: Text("Category"),
              // onTap: () {
              //   foodNotifier.currentRecipe = foodNotifier.recipelist[index];
              //   Navigator.of(context).push(MaterialPageRoute(builder: (BuildContext context){
              //     return FoodDetail();
              //   }));
              // },
            );
          },
          itemCount: ToolsUtilities.imageRecipe.length,
          separatorBuilder: (BuildContext context, int index){
            return Divider(
              color: Colors.black,
            );
          },
        ),
    );
  }
}

This is my firebase and recipe collection:

Answer 1

First get a reference to your collection as a field in your StatefulComponent:

final Stream<QuerySnapshot<Map<String, dynamic>>> _myStream = FirebaseFirestore.instance
      .collection('recipes')
      .snapshots();

Once you got it create a StreamBuilder component passing the collection as a stream and using it within a builder:

child: StreamBuilder<QuerySnapshot<Map<String, dynamic>>>(
    stream: _myStream,
    builder: (context, snapshot) {
        //your code goes here
    }
)

To use it you have to:

• make sure that there is any data
• make sure there were no errors

So the code looks like this:

child: StreamBuilder<QuerySnapshot<Map<String, dynamic>>>(
    stream: _myStream,
    builder: (context, snapshot) {
        if (snapshot.hasError) { //check for errors
            return const Text('Something went wrong');
        }

        if (snapshot.connectionState == ConnectionState.waiting) { //connection is still being set up
            return const CircularProgressIndicator();
        }

        if (snapshot.hasData) { // wait for data
            return const CircularProgressIndicator();
        }

        var data = snapshot.data!.docs.map((document) {
             return RecipeModel.fromMap(document);
        }).toList();

        return ListView(
            //ListView code
        )

    }
)