我正在使用图像选择器在我的颤动应用程序中选择照片.

我的代码如下

import 'package:flutter/material.dart';
import 'package:onlinecity/component/TextField/inputField.dart';



import 'package:onlinecity/component/Button/roundedButton.dart';
import 'package:onlinecity/component/Button/textButton.dart';
import 'style.dart';
import 'package:onlinecity/theme/style.dart';
import 'package:flutter/services.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:image_picker/image_picker.dart';
import 'dart:async';
import 'dart:io';

class AddOfferScreen extends StatefulWidget {


  @override
  AddOfferScreenState createState() => new AddOfferScreenState();
}

class AddOfferScreenState extends State<AddOfferScreen> {
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
  bool _autovalidate = false;
  String _productTitle;
  String _category;
  String _contactNumber;
  Future<File> _imageFile;

  void _onImageButtonPressed(ImageSource source) {
    setState(() {
      _imageFile = ImagePicker.pickImage(source: source);
    });
  }

  _onPressed() {
    print("button clicked");
  }

  void showInSnackBar(String value) {
    _scaffoldKey.currentState
        .showSnackBar(new SnackBar(content: new Text(value)));
  }

  bool _handleSubmitted() {
    final FormState form = _formKey.currentState;
    if (form.validate()) {
      form.save();
      return true;
    }
    return false;
  }
  void validateAndSubmit() async{
    if (_handleSubmitted()){
      try {
        Firestore.instance.collection('todos').document().setData({"productTitle":_productTitle,"category":_category,"contactNumber":_contactNumber});

      }
      catch (e){
        print('Error: $e');
      }
    }

  }

  void _showaddphoto(){
    AlertDialog dialog = new AlertDialog(
      actions: <Widget>[
        new IconButton(icon: new Icon(Icons.camera_alt),onPressed: () => _onImageButtonPressed(ImageSource.camera),tooltip: 'Take a Photo'),new IconButton(icon: new Icon(Icons.sd_storage),onPressed:  () => _onImageButtonPressed(ImageSource.gallery),tooltip: 'Pick Image from gallery')

      ],);
    showDialog(context: context,child: dialog);

  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    Size screenSize = MediaQuery.of(context).size;
    //print(context.widget.toString());
    return new Scaffold(
        key: _scaffoldKey,body: new SingleChildScrollView(
          child: new Container(
            padding: new EdgeInsets.all(16.0),decoration: new BoxDecoration(image: backgroundImage),child: new Column(
              mainAxisAlignment: MainAxisAlignment.end,crossAxisAlignment: CrossAxisAlignment.center,children: <Widget>[
                new SizedBox(
                    height: screenSize.height / 2 + 20,child: new Column(
                      mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                        new Text(
                          "CREATE ACCOUNT",textAlign: TextAlign.center,style: headingStyle,)
                      ],)),new Column(
                  children: <Widget>[
                    new Form(
                        key: _formKey,autovalidate: _autovalidate,//onWillPop: _warnUserAboutInvalidData,child: new Column(
                          children: <Widget>[
                            new FutureBuilder<File>(
                              future: _imageFile,builder: (BuildContext context,AsyncSnapshot<File> snapshot) {
                                if (snapshot.connectionState == ConnectionState.done &&
                                    snapshot.data != null) {
                                  return new Image.file(snapshot.data);
                                } else if (snapshot.error != null) {
                                  return const Text('error picking image.');
                                } else {
                                  return const Text('You have not yet picked an image.');

                                }
                              },),new RaisedButton.icon(onPressed: _showaddphoto,icon: new Icon(Icons.add_a_photo),label: new Text('Add Photo')),new InputField(
                              hintText: "product title",obscureText: false,textInputType: TextInputType.text,textStyle: textStyle,textFieldColor: textFieldColor,icon: Icons.person_outline,iconColor: Colors.white,bottomMargin: 20.0,validateFunction: (value)=> value.isEmpty ? 'UserName can\'t be empty' : null,onSaved: (value)=> _productTitle = value,new InputField(
                              hintText: "Category",textInputType: TextInputType.emailAddress,icon: Icons.mail_outline,validateFunction: (value)=> value.isEmpty ? 'Email can\'t be empty' : null,onSaved: (value)=> _category = value,new InputField(
                              hintText: "Contact Number",obscureText: true,icon: Icons.lock_open,bottomMargin: 40.0,validateFunction: (value)=> value.isEmpty ? 'Contact number can\'t be empty' : null,onSaved:  (value)=> _contactNumber = value,new RoundedButton(
                                buttonName: "Continue",onTap: validateAndSubmit,width: screenSize.width,height: 50.0,bottomMargin: 10.0,borderWidth: 1.0)
                          ],new TextButton(
                      buttonName: "Terms & Condition",onPressed: _onPressed,buttonTextStyle: buttonTextStyle,)
                  ],)
              ],));
  }
}