SharedPreferences for Dark and Light Theme - Flutter Explained

#DarkTheme and #LightTheme is one of the most popular trends in 2020. This is for me reason enough to explain on the example the provider package in #Flutter. Today in #FlutterExplained we solve the mystery of how to implement and use the provider package to create a dark and light theme depending on the user's selection.

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[laszloszurok]

One thing I would like to add to this video. In the main function where you pass the boolean value to the constructor of the ThemeProvider from shared preferences, you have to do a null check. If a user performs a clean install of the app there is nothing in shared preferences, so the app will crash at startup. It is not happening in the video, because you saved the boolean data to shared preferences earlier, but if you would erase the cache of the app on your phone, it would fail to start up. So the very simple solution is the following:

create: (BuildContext context) => ThemeProvider(isDarkMode: prefs.getBool("isDarkTheme") ?? false

You just have to add this part : ' ?? false '
This means the following: If the value of prefs.getBool("isDarkTheme") is null (so there is no saved data), set the value of isDarkMode to false. Otherwise give it the value from shared preferences.
This way, if you perform a clean install, the app will launch just fine and the active them will be the light one. If the user then changes the theme, the app works as expected, because it will find the saved data in shared prefs.

Great videos btw, you helped me a lot to set up my dark and light theme, thanks :)

[jaituteja]

Sir please adding these video its help a lot plz don't stop

[LuisMartinez-senp]

Bro, i got stuck trying to change the theme and saved in the shared preferences, there was a lot of errors in my app but with this video everything looks more simple and easy, thanks for sharing this type of content, as a begginer in flutter, i really appreciate this, ty <3

[ThaiNguyen-dxnk]

The video sound is pretty good, beyond my imagination

[moshyfawn]

Hi! I can't make it to your streams but was really enjoying your videos. I've been creating an ultimate flutter seed with basic features that every production app would need. You helped me with a few topics very much. The only thing that I've been stuck on for a while now is testing. Do you know anything about this topic? Maybe some great written/video tutorials?

[MuzeTrends]

hello Sir, in the video you have class ChangeNotifierProvider, Consumer defined in a file called change_notifier but this is not in the git repo. And I can see its referenced, in the theme.dart and main.dart. Can you help?

[akshayv]

Can you help me in storing the qrvalue received after scanning the qrcode using the qrscan flutter package in pub.dev

[nomikhan]

how to implement this on all screens of your app??