Flutter Randomizing - How to prevent from displaying the previous element shown

Question

Upon clicking, my app shows either yes, no, or maybe. How do I set the subsequent result strictly different from the previous one? For example, the current result is 'no', how do I randomize and make sure that the next result would ONLY either be 'yes' or 'maybe'?

This is the code

import 'package:flutter/material.dart';
import 'dart:math';

void main() => runApp(
      MaterialApp(
        debugShowCheckedModeBanner: false,
        home: MyApp(),
      ),
    );

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: Scaffold(
        backgroundColor: Colors.white,
        appBar: AppBar(
          centerTitle: true,
          title: Text(
            'Ask Me Anything',
            style: TextStyle(fontFamily: 'Lobster', fontSize: 25),
          ),
        ),
        body: picker(),
      ),
    );
  }
}

class picker extends StatefulWidget {
  @override
  _pickerState createState() => _pickerState();
}

class _pickerState extends State<picker> {
  List yourList = ["Yes", "No", "Maybe"];
  int randomIndex;

  _pickerState() {
    randomIndex = Random().nextInt(yourList.length);
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: TextButton(
        onPressed: () {
          setState(() {
            randomIndex = Random().nextInt(yourList.length);
            print("What's showing is '${yourList[randomIndex]}'");
          });
        },
        child: Stack(
          children: <Widget>[
            Center(child: Image.asset('images/blu.png')),
            Center(
              child: Text(
                yourList[randomIndex],
                style: TextStyle(fontSize: 40, fontFamily: 'Lobster'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

matkv · Accepted Answer · 2020-10-24 17:52:29Z

1

You could just do a while loop which keeps trying for a new answer as long as the answer is equal to the current answer:

_pickerState() {
oldIndex = randomIndex;
randomIndex = Random().nextInt(yourList.length);
while (oldIndex == randomIndex){
   randomIndex = Random().nextInt(yourList.length);
}

And then in your onPressed:

 setState(() {
        randomIndex = _pickerState();
        print("What's showing is '${yourList[randomIndex]}'");
      });

edited Oct 24, 2020 at 17:52

answered Oct 22, 2020 at 13:03

matkv

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1 Comment

Pamela Over a year ago

How do I initialize oldIndex?

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