_CastError(对空值使用的空检查操作符)2023

Question

这是我输入的form wedget的代码，它不起作用

我正在为我的应用程序创建一个登录页面，并想验证我的笔记，我之前也写了相同的验证代码，但那次我没有得到任何错误。但这次我得到_CastError (Null检查操作符上使用的空值)，试图在谷歌上找到它，但不能颤振专家请帮助真的沮丧了。我附上的代码以及错误。

import 'dart:ffi';
import 'dart:io' as io;
import 'dart:io';
import 'dart:typed_data';
import 'dart:math';
import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:file_picker/file_picker.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:image_picker/image_picker.dart';
import 'package:realstate/app%20settings/dumyboutton.dart';
import 'package:realstate/app%20settings/text%20sittings.dart';
import 'package:realstate/home%20page/home.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:path_provider/path_provider.dart';
import 'package:http/http.dart' as http;
import '../app settings/textfildsittings.dart';
import 'dart:convert';
class Addingpage extends StatefulWidget {
const Addingpage({super.key});
@override
State<Addingpage> createState() => _AddingpageState();
}
class _AddingpageState extends State<Addingpage> {
final location = TextEditingController();
final detals = TextEditingController();
final expectedprice = TextEditingController();
final expectedrent = TextEditingController();
GlobalKey<FormState> formstate = GlobalKey<FormState>();
CollectionReference _reference =
FirebaseFirestore.instance.collection('Detabase');
String imageUrl = '';
final ImagePicker imagePicker = ImagePicker();
PickedFile? file;
var ref;
UploadTask? referenceImagetouplod;
addNotes() async {
var formdata = formstate.currentState;
if (formdata!.validate()) {

await ref.putFile(File(file!.path));
imageUrl = await ref.getDownloadURL();
await _reference.add({
"Location": location,
"detals": detals,
"expected price": expectedprice,
"expected rent": expectedrent
});
}
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
leading: IconButton(
icon: Icon(Icons.arrow_back, color: Colors.black),
onPressed: () => Navigator.of(context).pop(),
),
backgroundColor: Colors.white,
title: Text(
"Add Your Proberty",
style: TextStyle(color: Colors.black),
),
centerTitle: true,
),
resizeToAvoidBottomInset: false,
body: Form(
key: formstate,
child: Center(
child: ListView(
children: [
Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Padding(
padding: const EdgeInsets.only(
top: 60,
),
child: Container(
decoration: BoxDecoration(
color: Colors.white70,
border: Border.all(width: 5, color: Colors.white70),
borderRadius: BorderRadius.all(Radius.circular(7)),
),
width: MediaQuery.of(context).size.width * 0.90,
height: MediaQuery.of(context).size.height * 0.20,
//color: Colors.white70,
child: Padding(
padding: const EdgeInsets.all(10),
child: IconButton(
color: Colors.black,
onPressed: () {
Scaffold.of(context).showBottomSheet<void>(
(BuildContext context) {
return Container(
height: 200,
color: Colors.white,
child: Center(
child: Column(
mainAxisAlignment:
MainAxisAlignment.start,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(
right: 180,
top: 20,
),
child: TextButton.icon(
label: const Text('Camara',
style: TextStyle(
fontSize: 35,
color: Colors.black,
)),
onPressed: () async {
// ImagePicker imagePicker =
//     ImagePicker();
// XFile? file =
//     await imagePicker.pickImage(
//         source:
//             ImageSource.camera);
// print('${file?.path}');
// if (file == null) return;
// String uniqueFileName =
//     DateTime.now()
//         .millisecondsSinceEpoch
//         .toString();
// referenceDiImages =
//     FirebaseStorage.instance
//         .ref()
//         .child('files');
// Reference
//     referenceImagetouplod =
//     referenceDiImages
//         .child(uniqueFileName);
// try {
//   await referenceImagetouplod
//       .putFile(File(file.path));
//   imageUrl =
//       await referenceImagetouplod
//           .getDownloadURL();
// } catch (error) {}
},
icon: Icon(
Icons.photo_camera,
size: 35,
color: Colors.black,
)),
),
Padding(
padding: const EdgeInsets.only(
right: 190,
top: 30,
),
child: TextButton.icon(
label: const Text('Gallary',
style: TextStyle(
fontSize: 35,
color: Colors.black)),
onPressed: () async {
ImagePicker imagePicker =
ImagePicker();
XFile? file =
await imagePicker
.pickImage(
source:
ImageSource
.gallery);
print('${file?.path}');

String uniqueFileName =
DateTime.now()
.millisecondsSinceEpoch
.toString();
ref = FirebaseStorage.instance
.ref()
.child('files');
},
icon: Icon(
Icons
.photo_size_select_actual_outlined,
size: 35,
color: Colors.black,
)),
),
],
),
),
);
},
);
},
icon: Icon(
Icons.add_a_photo_outlined,
size: 35,
color: Colors.black,
),
),
),
),
),
Padding(
padding: const EdgeInsets.only(
top: 100,
right: 10,
left: 10,
bottom: 10,
),
child: Container(
width: MediaQuery.of(context).size.width * 0.90,
height: MediaQuery.of(context).size.height * 0.08,
child: TextFormField(
validator: (value) {
if (value!.length > 100) {
return "Max is 100 Charactors";
}
if (value.length < 4) {
return "Please Fill IN";
} else {
return null;
}
},
controller: location,
textAlignVertical: TextAlignVertical.bottom,
decoration: InputDecoration(
hintStyle:
GoogleFonts.adventPro(color: Colors.black),
hintText: "Location",
filled: true,
fillColor: Colors.white70,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10),
borderSide: BorderSide.none),
),
),
),
),
Padding(
padding: const EdgeInsets.all(10),
child: Container(
width: MediaQuery.of(context).size.width * 0.90,
height: MediaQuery.of(context).size.height * 0.15,
child: TextFormField(
validator: (value) {
if (value!.length > 200) {
return "Max is 100 Charactors";
}
if (value.length < 16) {
return "Please Fill IN";
} else {
return null;
}
},
controller: detals,
maxLines: 6,
autocorrect: true,
textAlignVertical: TextAlignVertical.bottom,
decoration: InputDecoration(
hintStyle:
GoogleFonts.adventPro(color: Colors.black),
hintText:
"Detals , Area , Any Problems About The Property",
filled: true,
fillColor: Colors.white70,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10),
borderSide: BorderSide.none),
),
),
),
),
Padding(
padding: const EdgeInsets.all(10),
child: Container(
width: MediaQuery.of(context).size.width * 0.90,
height: MediaQuery.of(context).size.height * 0.08,
child: TextFormField(
validator: (value) {
if (value!.length > 100) {
return "Max is 100 Charactors";
}
if (value.length < 4) {
return "Please Fill IN";
} else {
return null;
}
},
keyboardType: TextInputType.number,
controller: expectedprice,
textAlignVertical: TextAlignVertical.bottom,
decoration: InputDecoration(
hintStyle:
GoogleFonts.adventPro(color: Colors.black),
hintText: "Expected Price",
filled: true,
fillColor: Colors.white70,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10),
borderSide: BorderSide.none),
),
),
),
),
Padding(
padding: const EdgeInsets.all(10),
child: Container(
width: MediaQuery.of(context).size.width * 0.90,
height: MediaQuery.of(context).size.height * 0.08,
child: TextFormField(
validator: (value) {
if (value!.length > 100) {
return "Max is 100 Charactors";
}
if (value.length < 3) {
return "Please Fill IN";
} else {
return null;
}
},
keyboardType: TextInputType.number,
controller: expectedrent,
textAlignVertical: TextAlignVertical.bottom,
decoration: InputDecoration(
hintStyle:
GoogleFonts.adventPro(color: Colors.black),
hintText: "Expected Rent",
filled: true,
fillColor: Colors.white70,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10),
borderSide: BorderSide.none),
),
),
),
),
SizedBox(
height: 20,
),
Padding(
padding: const EdgeInsets.only(top: 20, bottom: 40),
child: Container(
width: MediaQuery.of(context).size.width * 0.80,
height: MediaQuery.of(context).size.height * 0.08,
child: ElevatedButton(
onPressed: () {
addNotes();
},
child: DummyText(
text: "Add Proberty",
),
style: ElevatedButton.styleFrom(
alignment: Alignment.center,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(30),
),
backgroundColor: Colors.white70,
)),
),
),
],
),
],
),
),
),
),
);
}
}

谢谢这是我在form wedget中输入的代码，它不起作用

type here

Answer 1

尝试以下代码:

onPressed: () {
if (file != null) {
addNotes();
}
},