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Question

I'm a beginner to flutter development, and working on Search functionality for the app, can anyone guide me why am I getting the following error:

======== Exception caught by widgets library ======================================================= The following NoSuchMethodError was thrown building SearchScreen(dirty, state: _SearchScreenState#1ec80): The getter 'length' was called on null. Receiver: null Tried calling: length

Here is my SearchScreen dart file code:

import 'package:flutter/material.dart';
import 'package:flutter_slidable/flutter_slidable.dart';
import 'package:fluttertravelapp/constants.dart';
import 'package:fluttertravelapp/models/new_category_model.dart';
import 'dart:ui';
import 'package:fluttertravelapp/widgets/bottom_navigation_bar.dart';
import 'package:google_fonts/google_fonts.dart';

class SearchScreen extends StatefulWidget {
  @override
  _SearchScreenState createState() => _SearchScreenState();
}

class _SearchScreenState extends State<SearchScreen> {


  List<NewCategoryModel> _foundedPlaces;


  onSearch(String search) {
    setState(() {
      _foundedPlaces = placesList(search);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      //bottomNavigationBar: BottomNavigationBarTravel(),
      body: SafeArea(
        child: Container(
          child: ListView(
            physics: BouncingScrollPhysics(),
            children: <Widget>[

              /// Custom Navigation Drawer and Search Button
              Container(
                height: 57.6,
                margin: EdgeInsets.only(top: 28.8, left: 28.8, right: 28.8),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: <Widget>[

                  ],
                ),
              ),

              /// Text Widget for Title
              Padding(
                padding: EdgeInsets.only(top: 0, left: 28.8),
                child: Text(
                  'Search',
                  style: GoogleFonts.playfairDisplay(
                      fontSize: 45.6, fontWeight: FontWeight.w700),
                ),
              ),

              AppBar(
                elevation: 0,
                backgroundColor: Colors.white,
                title: Container(
                  height: 48,
                  child: TextField(
                    style: TextStyle(
                      color: Colors.white,
                      fontSize: 20,
                      fontWeight: FontWeight.bold,
                    ),
                    onChanged: (value) => onSearch(value),
                    decoration: InputDecoration(
                        filled: true,
                        fillColor: kPrimaryColor,//Colors.grey[850],
                        contentPadding: EdgeInsets.all(0),
                        prefixIcon: Icon(Icons.search, color: Colors.white /*.grey.shade500,*/),
                        suffixIcon: Icon(Icons.clear, color: Colors.white /*.grey.shade500,*/),
                        border: OutlineInputBorder(
                            borderRadius: BorderRadius.circular(50),
                            borderSide: BorderSide.none
                        ),
                        hintStyle: TextStyle(
                            fontSize: 18,
                            fontWeight: FontWeight.normal,
                            color: Colors.white, //.grey.shade500

                        ),
                        hintText: "Search places"
                    ),
                  ),
                ),
              ),

              Container(
                color: Colors.white,
                child: _foundedPlaces.length == null ? ListView.builder(
                    itemCount: _foundedPlaces.length,
                    itemBuilder: (context, index) {
                      return Slidable(
                        actionPane: SlidableDrawerActionPane(),
                        actionExtentRatio: 0.25,
                        child: placeComponent(places: _foundedPlaces[index]),
                        actions: <Widget>[
                          new IconSlideAction(
                            caption: 'Archive',
                            color: Colors.transparent,
                            icon: Icons.archive,

                            onTap: () => print("archive"),
                          ),
                          new IconSlideAction(
                            caption: 'Share',
                            color: Colors.transparent,
                            icon: Icons.share,
                            onTap: () => print('Share'),
                          ),
                        ],
                        secondaryActions: <Widget>[
                          new IconSlideAction(
                            caption: 'More',
                            color: Colors.transparent,
                            icon: Icons.more_horiz,
                            onTap: () => print('More'),
                          ),
                          new IconSlideAction(
                            caption: 'Delete',
                            color: Colors.transparent,
                            icon: Icons.delete,
                            onTap: () => print('Delete'),
                          ),
                        ],
                      );
                    }) : Center(child: Text("No places found", style: TextStyle(color: Colors.black),)),
              ),
            ],
          ),
        ),
      ),
    );
  }

  placeComponent({NewCategoryModel places}) {
    return Container(
      margin: EdgeInsets.symmetric(horizontal: 20),
      padding: EdgeInsets.only(top: 10, bottom: 10),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Row(
              children: [
                Container(
                    width: 60,
                    height: 60,
                    child: ClipRRect(
                      borderRadius: BorderRadius.circular(50),
                      child: Image.network(places.image),
                    )
                ),
                SizedBox(width: 10),
                Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(places.placeName, style: TextStyle(color: Colors.white, fontWeight: FontWeight.w500)),
                      SizedBox(height: 5,),
                      Text(places.cityName, style: TextStyle(color: Colors.grey[500])),
                    ]
                )
              ]
          ),
        ],
      ),
    );
  }

}

What I think I'm getting the error here in my if else condition:

child: _foundedPlaces.length == null ? ListView.builder(
                    itemCount: _foundedPlaces.length,
                    itemBuilder: (context, index) {
                      return Slidable(
                        actionPane: SlidableDrawerActionPane(),
                        actionExtentRatio: 0.25,
                        child: placeComponent(places: _foundedPlaces[index]),
                        actions: <Widget>[
                          new IconSlideAction(
                            caption: 'Archive',
                            color: Colors.transparent,
                            icon: Icons.archive,

                            onTap: () => print("archive"),
                          ),
                          new IconSlideAction(
                            caption: 'Share',
                            color: Colors.transparent,
                            icon: Icons.share,
                            onTap: () => print('Share'),
                          ),
                        ],
                        secondaryActions: <Widget>[
                          new IconSlideAction(
                            caption: 'More',
                            color: Colors.transparent,
                            icon: Icons.more_horiz,
                            onTap: () => print('More'),
                          ),
                          new IconSlideAction(
                            caption: 'Delete',
                            color: Colors.transparent,
                            icon: Icons.delete,
                            onTap: () => print('Delete'),
                          ),
                        ],
                      );
                    }) : Center(child: Text("No places found", style: TextStyle(color: Colors.black),)),

Kindly help!!!!!!

Answer 1

length couldn't be null.you should change condition this way _foundedPlaces.length ==0 or _foundedPlaces.length <= 0