Android Development with Kotlin

Preference binding

To show more complex examples, we will present one that helps with SharedPreferences usage. There are better Kotlin approaches to this problem, but this examples is nice to analyze, and it is a reasonable example of property delegate usage on the extension property. As a result, we want to be able to treat the values saved in SharedPreferences as if they were properties of a SharedPreferences object. Here is an example usage:

    preferences.canEatPie = true 
    if(preferences.canEatPie) { 
        // Code 
    } 

Here are the examples for extension property definitions:

    var SharedPreferences.canEatPie:     Boolean by bindToPreferenceField(true) // 1    
    var SharedPreferences.allPieInTheWorld:     Long by bindToPreferenceField(0,"AllPieKey") //2