length() is giving errors
hey guys i have some error in this code whin i open this page it show this error
i know becuse the table there is no data in the table but i want to escape this error how i do it?
i tried everything in the code but nothing work i tried to put inNotEmpty but when i tried to add data in the table still nothing show this is my code:
import 'package:flutter/material.dart';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
class sections_KSU extends StatefulWidget {
@override
State<sections_KSU> createState() => _sections_KSUState();
}
List<String> disciplines = [
'الهندسة',
'العلوم الطبيعية',
'العلوم الاجتماعية',
'العلوم الإنسانية',
'العلوم الإدارية',
'التربية',
'الطب والعلوم الصحية',
'القانون',
'الفن والتصميم',
'الزراعة والدراسات البيئية',
];
List list = [];
class _sections_KSUState extends State<sections_KSU> {
get controller => null;
var pr1;
Future ReadData() async {
var url = "https://***.***.***.**/getksu.php";
var res = await http.get(Uri.parse(url));
if (res.statusCode == 200) {
var red = jsonDecode(res.body);
setState(() {
list = red;
});
} else {
Text("No ads right now");
}
}
@override
void initState() {
super.initState();
GetData();
}
GetData() async {
await ReadData();
}
Widget build(BuildContext context) {
return Scaffold(
body:SafeArea(
child: Column(
children: [
Container(
margin: EdgeInsets.only(left: 70, right: 60),
height: 56.0,
width: 245.0,
child: Container(
decoration: BoxDecoration(
border: Border.all(color: Color(0xffF4AC47), width: 5),
color: Color(0xff42A9D2),
borderRadius: BorderRadius.only(
bottomLeft: Radius.circular(40),
bottomRight: Radius.circular(40))),
child: new Center(
child: new Text(
"جامعة الملك سعود",
style: TextStyle(
fontSize: 25,
color: Color(0xff072A52),
fontFamily: 'Cairo'),
textAlign: TextAlign.center,
),
///end logo
)),
),
SizedBox(
height: 35,
),
///Search
Container(
width: 390,
height: 69,
decoration: BoxDecoration(
border: Border.all(color: Color(0xff072A52), width: 5),
borderRadius: BorderRadius.only(
bottomLeft: Radius.circular(15),
bottomRight: Radius.circular(15),
topLeft: Radius.circular(15),
topRight: Radius.circular(15))),
child: Column(
children: [
Container(
child: (TextField(
controller: controller,
decoration: InputDecoration(
prefixIcon: const Icon(Icons.search),
hintText: 'Search',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(5))),
)),
),
],
)),
///search end
SizedBox(
height: 10,
),
/// icon filter
Row(
children: [
TextButton(onPressed: (){dd();}, child:dd())
],
),
/// icon filter end
///start Section
///
Expanded(
child: ListView.builder(
itemCount:list.length,
itemBuilder: ((cts, i) {
return Column(
children: [
Container(
margin: const EdgeInsets.symmetric(horizontal: 10),
height: 160.0,
child: Container(
decoration: BoxDecoration(
border: Border.all(
color: Colors.blueGrey, width:2),
borderRadius: BorderRadius.circular(8)),
child:TextButton(///
onPressed: (){},
child:Container(
child: Column(
children: [
Row(
children: [
const Expanded(
flex: 3,
child: Image(
image: AssetImage("assets/book.jpg"),height:130,
),
),
Expanded(
flex: 9,
child: Column(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
"${list[i]["book_name"]}",
style: TextStyle(
fontSize: 25, color: Colors.green),
),
const SizedBox(height: 65),
Row(
mainAxisAlignment: MainAxisAlignment.end,
children: [
Text("${list[i]["collage"]}",style:TextStyle(fontSize:16)),SizedBox(width:10,),
const Icon(Icons.perm_identity_rounded,color:Colors.teal,),
SizedBox(width:60,),
Text("${list[i]["loc"]}",style:TextStyle(fontSize:15),),SizedBox(width:10,),
const Icon(Icons.person_pin_circle,color:Colors.teal,),SizedBox(width: 10,)
],
),
],
),
)
],
),
],
),
),
)
),
),
const SizedBox(height: 26),
],
);
}),
),
),
],
),
)
);
}
}
///flter
class dd extends StatefulWidget {
const dd({Key? key}) : super(key: key);
@override
State<dd> createState() => _ddState();
}
class _ddState extends State<dd> {
List<String> disciplines = [
'الهندسة',
'العلوم الطبيعية',
'العلوم الاجتماعية',
'العلوم الإنسانية',
'العلوم الإدارية',
'التربية',
'الطب والعلوم الصحية',
'القانون',
'الفن والتصميم',
'الزراعة والدراسات البيئية',
];
get TitleName => "التخصصات";
///يطبع التخصص المختار
set UnaverNAME(String UnaverNAME) {print(UnaverNAME);}
set selectItem(String selectItem) {}
@override
Widget build(BuildContext context) {
return SizedBox(
width: 168,height:60,
child: Padding(
padding: const EdgeInsets.only(left:8),
child: Center(
child: DropdownButtonFormField<String>(
decoration: InputDecoration(
focusedBorder: OutlineInputBorder(
borderRadius: BorderRadius.circular(40),
borderSide: BorderSide(color: Color(0xff072A52), width: 2),
),
enabledBorder: OutlineInputBorder(
borderRadius: BorderRadius.circular(40),
borderSide: BorderSide(width: 2, color: Color(0xff072A52)))),
hint: Center(
child: Text(
" $TitleName",
// " اسم الجامعة",
style: TextStyle(
fontWeight: FontWeight.w800,
fontSize: 16,
color: Color.fromRGBO(244, 172, 71, 1)),
)),
// value: selectItem,
items: disciplines
.map((item) => DropdownMenuItem(
value: item,
child: Text(item,
style: TextStyle(
fontSize: 12,
color: Color.fromRGBO(244, 172, 71, 1),
fontWeight: FontWeight.w900))))
.toList(),
onChanged: (value) {
setState(() {
selectItem = value!;
UnaverNAME = value;
});
},
),
),
),
);
}
}
and this is my php code:
<?php
include("config.php");
$sql = "SELECT book_name,loc,com,spe,collage FROM ads where collage = 'جامعة الملك سعود' ";
$res = $connect->query($sql);
if ($res >= 1) {
while($row = $res -> fetch_assoc()) {
$data[]=$row;
}
echo json_encode($data);
} else {
echo json_encode("sorry this is no ads know");
}
$mysqli_connect-> close();
?>
Comments:
2023-01-19 23:01:05
Your PHP code produces ambiguous output. Sometimes it produces an array, other times it produces a string. Stick to a single data type. Let it always return an array, an empty array if it cannot find any data in the database. Return the error in the HTTP status code (
http_response_code(404);). 2023-01-19 23:01:05
Assuming that the type of
$connect is mysqli (it is not clear from your code), the value returned by $connect->query() is either an object of type mysqli_result() or false. Comparing any of these with 1 is not the right way to check it. Use if ($res !== false). When $res is false there is a problem with your query and the PHP script should return 500 Server Error, not 200 OK. Answers(1) :
I believe its coming from this line: itemCount:list.length,
And its because at this point of the code your list is null. It doesn't have any data.
I think you need to swap these around:
List list = [];
List<String> disciplines = [
'الهندسة',
'العلوم الطبيعية',
'العلوم الاجتماعية',
'العلوم الإنسانية',
'العلوم الإدارية',
'التربية',
'الطب والعلوم الصحية',
'القانون',
'الفن والتصميم',
'الزراعة والدراسات البيئية',
];
It looks like you are defining list then you are instantly setting it to a blank array.
If you call .length on a blank array it will throw this error you are getting.