如何从函数内部检索 Firestore 数据？

Question

我正在尝试通过按钮在函数内调用 Firestore 数据，即集合的标题。当我只是在 onPressed 中使用它时它起作用了：

Expanded(
   child: IconButton(
      icon: Icon(
        Icons.share,
         onPressed: () => Share.share(
         '${(snapshot.data.documents[index]['title'])}',  //this displays the 'title' 
fields of my firestore collections in ListView
         ))),

但是当试图从一个函数（在不同的共享插件中）调用时，无论我尝试什么都只是打印实际代码而不是内容，我如何在下面的函数中检索 firestore 集合的“标题”，我想字符串插值 ${ like this } 是唯一的方法，但它不适用于此：

MaterialButton(
              child: Text('Share text'),
              onPressed: () async => await _shareText(),
            ),

功能：

Future<void> _shareText() async {
try {
  Share.text('my text title',
      'HERE => This is my text to share with other applications.', 'text/plain');  
// no variation of ${snapshot.data.documents[index]['title']} works here
} catch (e) {
  print('error: $e');
}}

我得到数据的字符串是：

${snapshot.data.documents[index]['title']} 

还有其他方法可以调用它吗？

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter_staggered_grid_view/flutter_staggered_grid_view.dart';
import 'dart:ui';
import 'package:google_fonts/google_fonts.dart';
import 'package:material_design_icons_flutter/material_design_icons_flutter.dart';
import 'package:esys_flutter_share/esys_flutter_share.dart';
import 'dart:async';
import 'image.dart';


class Recipe extends StatefulWidget {
@override
_RecipeState createState() => _RecipeState();
}

class _RecipeState extends State<Recipe> {
 var firestoreDb = Firestore.instance.collection("recipes").snapshots();



  // THIS ${(snapshot.data.documents[index].data['title'])} does not work in 
  share plugin:
Future<void> _shareText() async {
try {
  Share.text('Share Text ',
      '${(snapshot.data.documents[index].data['title'])}', 'text/plain');
} catch (e) {
  print('error: $e');
}
}

@override
Widget build(BuildContext context) {
return Scaffold(
  appBar: AppBar(
    title: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          Container(
              padding: const EdgeInsets.all(8.0),
              child: Text(
                'Recipes',
                style: GoogleFonts.lato(
                  fontSize: 22.0,
                  color: Colors.amberAccent.shade50,
                ),
              )),
          IconButton(
            icon: Icon(MdiIcons.foodForkDrink, color: Color(0xffffe0b2), 
size: 32.0),
            onPressed: () {
             null;
            },
          ),
        ]),
    backgroundColor: Colors.lightBlue,
    elevation: 50.0,
  ), //AppBar

  body: Container(
    width: MediaQuery.of(context).size.width,
    child: StreamBuilder(
        stream: firestoreDb,
        builder: (context, snapshot) {
          if (!snapshot.hasData) Text('Loading...');
          return StaggeredGridView.countBuilder(
            crossAxisCount: 2,
            mainAxisSpacing: 1.0,
            crossAxisSpacing: 1.0,
            padding: EdgeInsets.symmetric(horizontal: 2.0, vertical: 6.0),
            shrinkWrap: true,
            itemCount: snapshot.data.documents.length,
            itemBuilder: (context, int index) => Container(
              child: Column(
                children: <Widget>[
                  Card(
                    color: Colors.white,
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(12.0),
                    ),

                    child: Column(children: <Widget>[
                      ListTile(
                        title: Text(
                          '${(snapshot.data.documents[index]['title'])}',
                          style: GoogleFonts.lato(
                            fontSize: 20.0,
                            height: 1.2,
                            fontWeight: FontWeight.w500,
                          ),
                          textAlign: TextAlign.center,
                        ),

                        subtitle: Row(
                            mainAxisSize: MainAxisSize.max,
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: <Widget>[



                              MaterialButton(
                                child: Text('Share text'),
                                onPressed: () async => await _shareText(),
                              ),

                              SizedBox(height: 5.0),
                              ImageInput(),  //this displays image called 
from image_picker to share , it works for sharing an image. 


                              Expanded(
                                child: Text(
                                  '${(snapshot.data.documents[index] 
   ['subtitle'])}',
                                  textAlign: TextAlign.right,
                                  style: GoogleFonts.lato(
                                    fontSize: 13.0,
                                    fontWeight: FontWeight.w900,
                                    fontStyle: FontStyle.italic,
                                    color: Colors.blue,
                                  ),
                                ), //subtitle: Text
                              ),
                            ] //children
                        ), //Row
                      ), //listtile
                    ]),
                  ),
                ],
              ),
            ),
            staggeredTileBuilder: (int index) => StaggeredTile.fit(2),
          );
        }),
  ),
);
} //build
} //class

我将 ImageInput() 类页面复制到主页中，因为我无法同时共享图像和文本，我仍然在共享文本字段中看到文本和快照的“未定义”错误。尽管它现在在同一页面上，但同样的修复不适用于文本。我究竟做错了什么？

MaterialButton(
      child: Text('Send it!'),
      onPressed: () async => await _shareImageAndText(snapshot, index),
    ),

---

Future<void> _shareImageAndText(snapshot, index) async {
try {
  List<int> imageBytes = await _imageFile.readAsBytes();
  var uint8List = Uint8List.fromList(imageBytes);
  await Share.file('esys image', 'esys.jpg', uint8List, 'image/jpeg',
      text: (snapshot.data.documents[index].data['title']) );
      //text: 'My optional text.');
  // (snapshot.data.documents[index].data['title']), 'text/plain');
  } catch (e) {
  print('error: $e');
  }}

---

class ImageInput extends StatefulWidget {
@override
_ImageInputState createState() => _ImageInputState();
}

class _ImageInputState extends State<ImageInput> {

 File _imageFile;

 void _getImage(BuildContext context, ImageSource source){
ImagePicker.pickImage(source: source, maxWidth: 200.0).then((File image){
  setState((){
    _imageFile = image;
  });
  Navigator.pop(context);

});
 }

  void _openImagePicker(BuildContext context) {
 showModalBottomSheet(context: context, builder: (BuildContext context) {
  return Container(
    height: 180.0,
    padding: EdgeInsets.all(10.0),
    child: Column(
        children: [
          Text('Choose photo',
            style:TextStyle(fontWeight: FontWeight.bold),),
          SizedBox(height: 10.0),
          FlatButton(
            textColor: Theme.of(context).primaryColor,
            child: Text('Use Camera'),
            onPressed: () {
              _getImage(context, ImageSource.camera);
            },),
          FlatButton(
            textColor: Theme.of(context).primaryColor,child:
          Text('Open Gallery'),
            onPressed: () {
              _getImage(context, ImageSource.gallery);
            },)

        ]
    ),);
});
}

  @override
  Widget build(BuildContext context) {
  return Column(
  children: <Widget>[
    OutlineButton(
      onPressed: () {
        _openImagePicker(context);
      },
      child:Row(
          mainAxisAlignment: MainAxisAlignment.start,
          children: <Widget>[
            Icon(Icons.camera_alt),
            SizedBox(
              width:1.0,
            ),
            // Text('Add Image'),
          ]
      ),//Row
    ),//outline button

    SizedBox(height: 10.0),
    _imageFile == null ? Text('Add a Pic')  : Image.file(_imageFile,
      fit: BoxFit.cover,
      height: 200.0,
      width: 200.0,
      // width: MediaQuery.of(context).size.width,
      alignment: Alignment.topCenter,
    ),

    MaterialButton(
      child: Text('Send it!'),
      onPressed: () async => await _shareImageAndText(),

    ),
  ],
);
}
}

Answer 1

Future<void> _shareText(snapshot, index) async {
try {
  Share.text('Share Text ',
      (snapshot.data.documents[index].data['title']), 'text/plain');
} catch (e) {
  print('error: $e');
}
}

并在 StreamBuilder 中传递快照参数，这样调用它，

onPressed: () async => await _shareText(snapshot, index),