1-) FLUTTER - Stepper(adım adım) Widget Kullanımı

**** BASİT STEPPER KULLANIMI ****

BU LİNKE KESİN BAK : https://stackoverflow.com/questions/52828424/flutter-stepper-onstepcontinue-not-firing

import 'package:flutter/material.dart';

class StepperPageGelismis extends StatefulWidget {
  const StepperPageGelismis({Key? key}) : super(key: key);

  @override
  _StepperPageState createState() => _StepperPageState();
}

class _StepperPageState extends State<StepperPageGelismis> {
  int _aktifStep = 0;
  String isim = "", mail = "", sifre = "";
  late List<Step> tumStepler;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    tumStepler = tumSteplerGetir();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: SingleChildScrollView(
          child: Stepper(

physics: ClampingScrollPhysics(),
        steps: tumStepler,
        currentStep: _aktifStep,
        onStepTapped: (tiklanilanStep) {
          setState(() {
            _aktifStep = tiklanilanStep;
          });
        },
        onStepContinue: () {
          if (_aktifStep < tumStepler.length - 1) {
            setState(() {
              _aktifStep++;
            });
          }
        },
        onStepCancel: () {
          if (_aktifStep > 0) {
            setState(() {
              _aktifStep--;
            });
          }
        },
      )),
    );
  }

  List<Step> tumSteplerGetir() {
    List<Step> stepler = [
      Step(
        title: Text("username giriniz"),
        subtitle: Text("Alt içerik"),
        isActive: true,
        // seçili olan
        state: StepState.indexed,
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "UsernameLabel"),
          ),
        ),
      ),
      Step(
        title: Text("mail giriniz"),
        subtitle: Text("mail Alt içerik"),
        isActive: true,
        // seçili olan
        state: StepState.indexed,
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "UsernameLabel"),
          ),
        ),
      ),
      Step(
        title: Text("şifre giriniz"),
        subtitle: Text("şifre içerik"),
        isActive: true,
        // seçili olan
        state: StepState.indexed,
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "UsernameLabel"),
          ),
        ),
      ),
    ];

    return stepler;
  }
}

**** GELİŞMİŞ STEPPER KULLANIMI ****

import 'package:flutter/material.dart';

class StepperPageGelismis extends StatefulWidget {
  const StepperPageGelismis({Key? key}) : super(key: key);

  @override
  _StepperPageState createState() => _StepperPageState();
}

class _StepperPageState extends State<StepperPageGelismis> {
  int _aktifStep = 0;
  String username = "", mail = "", sifre = "";
  late List<Step> tumStepler;
  final key0 = GlobalKey<FormFieldState>();
  final key1 = GlobalKey<FormFieldState>();
  final key2 = GlobalKey<FormFieldState>();
  bool hata = false;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

  }

  @override
  Widget build(BuildContext context) {
    tumStepler = tumSteplerGetir();

    return Container(
      child: SingleChildScrollView(
          child: Stepper(
        steps: tumStepler,
        currentStep: _aktifStep,
        // onStepTapped: (tiklanilanStep) {
        //   setState(() {
        //     _aktifStep = tiklanilanStep;
        //   });
        // },
        onStepContinue: () {
          _ileriButtonKontrol();
        },
        onStepCancel: () {
          if (_aktifStep > 0) {
            setState(() {
              _aktifStep--;
            });
          }
        },
      )),
    );
  }

  List<Step> tumSteplerGetir() {
    List<Step> stepler = [
      Step(
        title: Text("username giriniz"),
        subtitle: Text("Alt içerik"),
        isActive: true,
        // seçili olan
        state: _stateleriAyarla(0),
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            key: key0,
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "UsernameLabel"),
            validator: (girilenDeger) {
              if (girilenDeger!.length < 6) {
                return "En az 6 karakter giriniz";
              }
            },
            onSaved: (girilenDeger) {
              username = girilenDeger!;
            },
          ),
        ),
      ),
      Step(
        title: Text("mail giriniz"),
        subtitle: Text("mail Alt içerik"),
        isActive: true,
        // seçili olan
        state: _stateleriAyarla(1),
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            key: key1,
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "mail"),
            validator: (girilenDeger) {
              if (girilenDeger!.length < 6) {
                return "En az 6 karakter giriniz";
              }
            },
            onSaved: (girilenDeger) {
              mail = girilenDeger!;
            },
          ),
        ),
      ),
      Step(
        title: Text("şifre giriniz"),
        subtitle: Text("şifre içerik"),
        isActive: true,
        // seçili olan
        state: _stateleriAyarla(2),
        // numara gözükür
        content: Padding(
          padding: EdgeInsets.only(top: 5),
          child: TextFormField(
            key: key2,
            decoration: InputDecoration(
                border: OutlineInputBorder(), labelText: "şifre"),
            validator: (girilenDeger) {
              if (girilenDeger!.length < 6) {
                return "En az 6 karakter giriniz";
              }
            },
            onSaved: (girilenDeger) {
              sifre = girilenDeger!;
            },
          ),
        ),
      ),
    ];

    return stepler;
  }

  StepState _stateleriAyarla(int oankiStep) {

    if (_aktifStep == oankiStep) {
      if (hata) {
        return StepState.error;
      } else {
        return StepState.editing;
      }
    } else {
      return StepState.complete;
    }
  }

  void _ileriButtonKontrol() {
    setState(() {
      switch(_aktifStep){
        case 0:
          if(key0.currentState!.validate()){
            key0.currentState!.save();
            hata=false;
            _aktifStep=1;
          }else{
            hata=true;
          }
          break;
        case 1:
          if(key1.currentState!.validate()){
            key1.currentState!.save();
            hata=false;
            _aktifStep=2;
          }else{
            hata=true;
          }
          break;
        case 2:
          if(key2.currentState!.validate()){
            key2.currentState!.save();
            hata=false;
            _aktifStep=2;
            formTamamlandi();
          }else{
            hata=true;
          }
          break;
      }
    });

  }

  void formTamamlandi() {
    print("başarılı ad : $username mail : $mail şifre : $sifre");
  }

}