小编Hit*_*goi的帖子

我有两个按钮，如果该字段存在，则它显示一个按钮，否则它显示用户其他按钮，其中我将提供将数据添加到我的数据库的功能...我正在使用云 Firebase ...如何检查该字段是否存在或不...下面是我的代码...

//如果分数不存在，它将显示一个凸起的按钮，以便您可以单击该按钮

//代码：

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

BuildContext buildContext;
int filter = 0;
StreamSubscription<DocumentSnapshot> subscription;

class ScorePage extends StatelessWidget {

  final int score;
  ScorePage({Key key, @required this.score}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: AppBar(
          title: new Text('Scroe Card'),
        ),
        body: new Center(
            child: new Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: <Widget>[
                  new Padding(padding: EdgeInsets.all(30.0)),
                  new MaterialButton(
                    color: Colors.red,
                    onPressed: () {},
                    child: new Text(
                      "Reset Quiz",
                    ),
                  ),
                  new Flexible(
                      child: StreamBuilder( …

我正在使用 flutter gridview 项目，我想在一定数量的索引之后显示另一个小部件。

如何在 gridview 的每 6 个索引之后添加小部件

GridView.builder(shrinkWrap: true,gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2,childAspectRatio: MediaQuery.of(context).size.width /
            (MediaQuery.of(context).size.width*0.9),),
            physics: NeverScrollableScrollPhysics(),


            itemCount: widget.dicovervehiclelist.length,
            itemBuilder: (BuildContext context, int index) {
              return vehicleview(
                  widget.dicovervehiclelist[index], context,widget.dicovervehiclelist.length,index);
            }),

我在下面的代码中有一个底部表格，其中我将高度设置为300.0，但是当用户滚动时我想将高度增加到全屏..我该怎么做..请

void _showBottomSheet() {
    setState(() {
      _showPersBottomSheetCallBack = null;
    });

    _scaffoldKey.currentState
        .showBottomSheet((context) {
      return new Container(
        height: 300.0,
        color: Colors.greenAccent,
        child: new Center(
          child: new Text("Hi BottomSheet"),
        ),
      );
    })
        .closed
        .whenComplete(() {
      if (mounted) {
        setState(() {
          _showPersBottomSheetCallBack = _showBottomSheet;
        });
      }
    });
  }

我正在开发 Flutter 应用程序，我想将 PDF 文件上传到 Firebase 存储，我使用 Documents_picker 选择文件，但无法将其上传到存储...请帮助我...我的代码如下

uploaddoc()async{


   dynamic docPaths;
   // Platform messages may fail, so we use a try/catch PlatformException.
   try {
     docPaths = await DocumentsPicker.pickDocuments;
     final Directory tempDir = Directory.systemTemp;
     final String fileName = "${Random().nextInt(10000)}.pdf";
     final File file = File('${tempDir.path}/$fileName');
     file.writeAsBytesSync(docPaths);

     final StorageReference ref = FirebaseStorage.instance.ref().child(fileName);
     final StorageUploadTask task = ref.putFile(file);
     final Uri downloadUrl = (await task.future).downloadUrl;
     _path = downloadUrl.toString();

     print(_path);
   } on PlatformException {

   }

   // If the widget was removed from the tree while …