There is no problem with the codes but when I run
I get error owner._debugCurrentBuildTarget == this is not true how can i solve this problem
class HomePage extends StatelessWidget{
#override
HomePageState createState() => HomePageState();
#override
dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
}
class HomePageState extends State{
late int first, second;
late String islem;
late String result, sonuc;
I think you are missing the StatefulWidget format, try
class HomePage extends StatefulWidget {
const HomePage({super.key});
#override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
late int first, second;
late String islem;
late String result, sonuc;
#override
void initState() {
super.initState();
first = 1;
second = 2;
islem = "islem";
result = "A";
sonuc = "sonuc";
}
#override
Widget build(BuildContext context) {
return Container();
}
}
Related
I stumped into a problem where I need to use a StatefulWidget parameter in its state class when it's constructed, but I couldn't find a way to do it since using widget.[whatever variable name] in the state's class constructor returns an unexpected null value, and the initState function only runs when the widget is being drawn to the screen.
For example:
import 'package:flutter/material.dart';
class Test extends StatefulWidget {
final String text;
Test(this.text);
final state = _TestState();
#override
_TestState createState() => state;
}
class _TestState extends State<Test> {
String? changingText;
void updateChangingText(String moreText){
changingText = changingText! + moreText;
}
#override
void initState() {
super.initState();
changingText = widget.text;
}
#override
Widget build(BuildContext context) {
return Text(changingText!);
}
}
class App extends StatelessWidget {
#override
Widget build(BuildContext context) {
var w = Test('test');
w.state.updateChangingText(' text');
return MaterialApp(home: Scaffold(body:
Test('test text')
));
}
}
void main() {
runApp(App());
}
This doesn't work since changingText is being updated before initState gives it its initial value since it only runs when Text is being drawn to the screen and this:
import 'package:flutter/material.dart';
class Test extends StatefulWidget {
final String text;
Test(this.text);
final state = _TestState();
#override
_TestState createState() => state;
}
class _TestState extends State<Test> {
String? changingText;
void updateChangingText(String moreText){
changingText = changingText! + moreText;
}
_TestState(){
changingText = widget.text;
}
#override
Widget build(BuildContext context) {
return Text(changingText!);
}
}
class App extends StatelessWidget {
#override
Widget build(BuildContext context) {
var w = Test('test');
w.state.updateChangingText(' text');
return MaterialApp(home: Scaffold(body:
Test('test text')
));
}
}
void main() {
runApp(App());
}
doesn't work either since you can't use widget.[whatever] in state class constructors (for some reason).
So what can I do to use widget parameters in the state class before the widget is drawn to the screen?
Thanks in advance for the help
You should use the initState method present in the State for this instead of the constructor
#override
void initState() {
changingText = widget.text;
super.initState();
}
Here you have part of my HomeScreen.dart file:
String _mi_email='';
String _mi_nombre='';
String _mis_apellidos='';
String _mi_foto='';
String _mi_clinica='';
String _mi_id='';
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
#override
Widget build(BuildContext context) {
void getValues() async {
SharedPreferences sharedPrefs = await SharedPreferences.getInstance();
_mi_email = sharedPrefs.getString('email');
_mi_clinica = sharedPrefs.getString('clinica') ?? "ninguna";
_mi_nombre = sharedPrefs.getString('nombre') ?? "ninguno";
_mis_apellidos = sharedPrefs.getString('apellidos') ?? "ningunos";
_mi_foto = sharedPrefs.getString('foto') ?? "ninguna";
_mi_id = sharedPrefs.getString('id') ?? "0";
}
#override
void initState() {
super.initState();
getValues();
}
...
What I need is to run getValues() every time when HomeScreen starts.
With my current code, it doesn't happen.
You need to write the initState method outside the build methord or inside the _HomeScreenState.
And your code will look like this
String _mi_email='';
String _mi_nombre='';
String _mis_apellidos='';
String _mi_foto='';
String _mi_clinica='';
String _mi_id='';
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
void getValues() async {
SharedPreferences sharedPrefs = await SharedPreferences.getInstance();
_mi_email = sharedPrefs.getString('email');
_mi_clinica = sharedPrefs.getString('clinica') ?? "ninguna";
_mi_nombre = sharedPrefs.getString('nombre') ?? "ninguno";
_mis_apellidos = sharedPrefs.getString('apellidos') ?? "ningunos";
_mi_foto = sharedPrefs.getString('foto') ?? "ninguna";
_mi_id = sharedPrefs.getString('id') ?? "0";
}
#override
void initState() {
getValues();
super.initState();
}
#override
Widget build(BuildContext context) {
...
You need to write method getValues(). into class _HomeScreenState not inside build.
In my project, I pass data from one widget to another using this code:
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
TranslatorSignUpStep2(transModel: this._translatorModel),
),
);
Then I retrive it in the other widget by the code below:
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State();
}
The problem is, in the TranslatorSignUpStep2 class I want to assign the passed-in transModel to another variable so I write this code
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
TranslatorModel _translatorModel = widget.transModel;
}
But it seems like the widget can't be used outside the build method so I get error saying
The instance member 'widget' can't be accessed in an initializer.. Anyone know how to get over this ?
you can access widget in initState function like this.
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
TranslatorModel _translatorModel ;
#override
void initState() {
_translatorModel = widget.transModel;
}
}
Just add the keyword late while initializing:
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State();
}
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
late TranslatorModel _translatorModel = widget.transModel;
}
try this code :
TranslatorSignUpStep2 :
class TranslatorSignUpStep2 extends StatefulWidget {
final TranslatorModel transModel;
TranslatorSignUpStep2({this.transModel});
#override
_TranslatorSignUpStep2State createState() => _TranslatorSignUpStep2State(this.transModel);
}
TranslatorSignUpStep2 class :
class _TranslatorSignUpStep2State extends State<TranslatorSignUpStep2> {
_TranslatorSignUpStep2State(TranslatorModel _tempModel ){
this._translatorModel =_tempModel;
};
TranslatorModel _translatorModel ;
}
Add static keyword when innitializing
class OrderDetails extends StatefulWidget {
int selectedDays;
OrderDetails({
this.range,)};
#override
_OrderDetailsState createState() => _OrderDetailsState();
}
class _OrderDetailsState extends State<OrderDetails> {
String getRange;
#override
void initState() {
super.initState();
getRange = widget.range;
}
I am passing an String from another StatefulWidget to the below CardItem StatefulWidget and then from here the String is passed to the _CardItemState as shown in the code below.
But how this String passed should be accessed from _CardItemState(String itemTitle);
class CardItem extends StatefulWidget {
String itemTitle;
CardItem({#required this.itemTitle});
#override
_CardItemState createState() => _CardItemState(itemTitle);
}
class _CardItemState extends State<CardItem> {
_CardItemState(String itemTitle);
void initState(){
print("INiatialize");
print("itemTitle is " + );
}
}
You can access it via widget.itemTitle. For your case you can call it like this:
printItem(){
print("itemTitle is ${widget.itemTitle}");
}
void initState(){
printItem();
super.initState();
}
You also don't need to pass the string in your state constructor. Remove this:
_CardItemState(String itemTitle);
easy! grab it using
widget.itemTitle
class CardItem extends StatefulWidget {
String itemTitle;
CardItem({#required this.itemTitle});
#override
_CardItemState createState() => _CardItemState(itemTitle);
}
class _CardItemState extends State<CardItem> {
String itemTitle; // - 1
_CardItemState(this.itemTitle); // - 2
void initState(){
itemTitle = widget.itemTitle; // - 3;
print("INiatialize");
print("itemTitle is " + itemTitle ); // - 4
print("itemTitle is " + widget.itemTitle ); // same as - 4
}
}
Best way to do this is to use
widget.fieldName
class CardItem extends StatefulWidget {
String itemTitle;
CardItem({#required this.itemTitle});
#override
_CardItemState createState() => _CardItemState(itemTitle:itemTitle);
}
class _CardItemState extends State<CardItem> {
String myItemTitle;
#override
void initState(){
super.initState();
myItemTitle=widget.itemTitle;
print("INiatialize");
print("itemTitle is $myItemTitle";
}
}
otherway round to this problem is to pass data in constructor as shown below, but the above method is recommended to be followed.
class CardItem extends StatefulWidget {
String itemTitle;
CardItem({#required this.itemTitle});
#override
_CardItemState createState() => _CardItemState(itemTitle:itemTitle);
}
class _CardItemState extends State<CardItem> {
String itemTitle;
_CardItemState({this.itemTitle});
void initState(){
print("INiatialize");
print("itemTitle is $itemTitle";
}
}
I want to access the variable UniversityId in the class of _HomePageState
class showDetailOfUniversity extends StatelessWidget {
final String UniversityId;
showDetailOfUniversity({Key key, #required this.UniversityId}) : super(key:
key);
#override
Widget build(BuildContext context)
{
return (
HomePage()
);
}
}
class HomePage extends StatefulWidget {
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
//
var temp2 = showDetailOfUniversity();
var temp = temp2.getUniversityId;
/// here i want to access the code but failed
}
The problem here is that you created another instance of showDetailOfUniversity that will have another values for its members. You did not initialize String UniversityId so its value is null untill you set it.
So when you called showDetailOfUniversity() in temp, the value of String UniversityId in this instance is null since there was no value given in this particular instance.
You can pass the String UniversityId in the constructor of the StatefulWidget like this:
class ShowDetailOfUniversity extends StatelessWidget {
final String universityId;
ShowDetailOfUniversity({Key key, #required this.universityId})
: super(key: key);
#override
Widget build(BuildContext context) {
return HomePage(universityId: universityId);
}
}
class HomePage extends StatefulWidget {
final String universityId;
const HomePage({Key key, this.universityId}) : super(key: key);
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
var universityId;
#override
void initState() {
super.initState();
universityId = widget.universityId;
}
#override
Widget build(BuildContext context) {
// TODO: implement build
return Text(universityId);
}
}
Solution for your code:
var temp2 = showDetailOfUniversity(UniversityId: university_id);
var temp = temp2.UniversityId; //this will return university_id