How to create a bool list in shared_preferences and store values ​there

Question

required this.favorite,

I got the bool value from the previous page like this. Since I used the pageview, I want to store the value in the index like this and use it later.

  loadFavorite() async{
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      favorite= prefs.getBoolList(_favoriteButton[index])!;
    });
  }


  void delete() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setBool(_favoriteButton[index], false);
    setState(() {
      favorite= prefs.getBool(_favoriteButton[index])!;
    });
  }

  void saved() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setBool(_favoriteButton[index], true);
    setState(() {
      favorite= prefs.getBool(_favoriteButton[index])!;
    });
  }

And I use the above code like this in the previous page. This is why I need a list. Without it I would have to create hundreds of pages.

  void loadFavorite() async{
    print(FavoriteButtons[0]);
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      favorite[0] = prefs.getBool(_favoriteButton[0])!;

Is it possible to create a list from shared_preferences? And how can I store bool as a list?

Solution 1

You can hold bool list by this method:

List<bool> favorite = <bool>[];

Future<void> loadFavorite() async{
  SharedPreferences prefs = await SharedPreferences.getInstance();
  setState(() {
    favorite = (prefs.getStringList("userFavorite") ?? <bool>[]).map((value) => value == 'true').toList();
  });
}

Future<void> delete() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  setState(() {
    favorite[index] = false;
  });
  await prefs.setStringList("userFavorite", favorite.map((value) => value.toString()).toList());
  setState(() {
    favorite = (prefs.getStringList("userFavorite") ?? <bool>[]).map((value) => value == 'true').toList();
  });
}

Future<void> saved() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  setState(() {
    favorite[index] = true;
  });
  await prefs.setStringList("userFavorite", favorite.map((value) => value.toString()).toList());
  setState(() {
    favorite = (prefs.getStringList("userFavorite") ?? <bool>[]).map((value) => value == 'true').toList();
  });
}

Solution 2

You can try using SharedPreferences.setStringList by saving only the true favorite button index to the list. Something like this (see comment for detail):

void save(int index, bool isFavorite) async {
   SharedPreferences prefs = await SharedPreferences.getInstance();
   var favorites = prefs.getStringList('favorites')??[];

   // index as string item
   var strIndex = index.toString();

   if(isFavorite) {
     // Save index to list only if it it not exist yet.
     if(!favorites.contains(strIndex)) {
        favorites.add(strIndex);
     }
   } else {
      // Remove only if strIndex exist in list.
      if(favorites.contains(strIndex)) {
        favorites.remove(strIndex); 
      }
   }

   // Save favorites back
   prefs.setStringList('favorites', favorites);
}

Future<bool> isFavorite(int index) async {
   SharedPreferences prefs = await SharedPreferences.getInstance();
   var favorites = prefs.getStringList('favorites')??[];

   // index as string item
   var strIndex = index.toString();

   // If index is exist, then it is must be true.
   if(favorites.contains(strIndex) {
      return true;
   }
   
   return false;  
}


 // All item index in list is always true
 Future<List<int>> getFavoriteIndexes() async {
   SharedPreferences prefs = await SharedPreferences.getInstance();
   var favorites = prefs.getStringList('favorites')??[];

   var indexes = <int>[];
   for(var favIndex in favorites) {
       // return -1 if invalid fav index found
       int index = int.tryParse(favIndex) ?? -1;
       if(val != -1) {
          indexes.add(index);
       }
   }

    return indexes;
 }

Please be aware, that the code haven't been tested yet.

Comments

[eno2]

Is the above code saved in this way 'favorite[index]'? The code is too long and I haven't figured it out yet.

[Røhäñ Dås]

Preferred to save encoded map as string using setString

[eno2]

How can I save a List<bool> favorite in (prefs.getStringList("userFavorite")? I get an error because List<bool> favorite is empty with [] on the first run of the app.

[Røhäñ Dås]

you can do null handling like this prefs.getStringList("userFavorite") ?? <bool>[]