Flutter Theme Changing dark to light using onpress event

Question

I am working with flutter projects and I want to change the themecolor using an onpressed event

I tried some code but not working.

main.dart file

import 'package:flutter/material.dart';
import 'Screens/HomePage.dart';

void main()=>  runApp(MyApp());

ThemeData _lightTheme = ThemeData(
  brightness: Brightness.light,
  primaryColor: Colors.white,
);
ThemeData _darkTheme = ThemeData(
  brightness: Brightness.light,
  primaryColor: Colors.white,
);
bool _ktheme = true;

class MyApp extends StatelessWidget {
 
 @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Wallbay',
      theme: _ktheme ? _lightTheme : _darkTheme,
      home: MyHomePage('Alpha Papers'),
    );
  }
}

HomePage.dart file

........
      IconButton(
        icon: Icon(Icons.brightness_medium_outlined),
        onPressed: () {
          setState(() {
            _ktheme = !ktheme;
          });
        },
      )
......

Solution

Your theme objects _lightTheme & _darkTheme are the same objects with different names.

They both have brightness set to Brightness.light & primaryColor as Colors.white.

ThemeData _lightTheme = ThemeData(
  brightness: Brightness.light, // <----
  primaryColor: Colors.white, // <----
);
ThemeData _darkTheme = ThemeData(
  brightness: Brightness.light, // <--- Dark mode having light brightness
  primaryColor: Colors.white, // <---- Dark mode having white color
);

Change these to the following:

ThemeData _lightTheme = ThemeData(
  brightness: Brightness.light, // light mode
  primaryColor: Colors.white,
);
ThemeData _darkTheme = ThemeData(
  brightness: Brightness.dark, // dark mode
  primaryColor: Colors.black,
);

Also, your onPressed code looks wrong.

setState(() {
  _ktheme = !_ktheme; // Notice: I renamed ktheme to _ktheme
});

Comments

[Randal Schwartz]

You can't just say "doesn't work". What does it do, and how is that different from your expectations, and what have yoouo tried when you're fixing it?

[Lakshmanan Kumar]

Thank you. But My Second Question is How to save this _ktheme variable on shared prefrences.

[Ravi Singh Lodhi]

Send me the question link & I will answer it there.

[Lakshmanan Kumar]

codepen