Krate

Krate is a SharedPreferences wrapper library that uses delegated properties for convenient access to SharedPreferences values.

Here's what its basic usage looks like, extending the SimpleKrate class:

class UserSettings(context: Context) : SimpleKrate(context) {

    var notificationsEnabled by booleanPref("notifications_enabled", false)
    var loginCount by intPref("login_count", 0)
    var nickname by stringPref("nickname", "")

}

val settings = UserSettings(context)
settings.loginCount = 10
Log.d("LOGIN_COUNT", "Count: ${settings.loginCount}")

Dependency

You can include Krate in your project from the mavenCentral() repository, like so:

implementation 'hu.autsoft:krate:0.1.2'

Optionals vs defaults

Each stored property can be declared with or without a default value. Here's how the two options differ:

Optional values:

A property declared with the one-argument delegate function will have a nullable type. It will have a null value if no value has been set for this property yet, and its current value can be erased from SharedPreferences completely by setting it to null.

var username: String? by stringPref("username")

Default values:

A property declared with the two-argument delegate function takes its default value as the second argument, and it will have a non-nullable type. Reading from this property will return either the value it was last set to or the default value. Setting this property will update the value stored in SharedPreferences. Note that there's no way to remove these values from SharedPreferences (although you could set it explicitly to the default value).

var username: String by stringPref("username", defaultValue = "admin")

Custom Krate implementations

You can usually get away with extending SimpleKrate, as it does allow you to pass in a custom name for the SharedPreferences to be used to store your values in its constructor as an optional parameter. (If you pass in no name parameter to its constructor, it will default to using the instance returned by PreferenceManager.getDefaultSharedPreferences(context).)

However, you can also implement the Krate interface directly if you want to manage the SharedPreferences instance yourself for whatever reason - all this interface requires is a property that holds a SharedPreferences instance. With that, you can use the delegate functions the same way as shown above:

class ExampleCustomKrate(context: Context) : Krate {

    override val sharedPreferences: SharedPreferences

    init {
        sharedPreferences = context.applicationContext.getSharedPreferences("custom_krate_prefs", Context.MODE_PRIVATE)
    }

    var exampleBoolean by booleanPref("exampleBoolean", false)
    
}

Addons

Krate, by default, supports the types that SharedPreferences supports. These are Boolean, Float, Int, Long, String and Set<String>. You may of course want to store additional types in Krate. For some common types, addon libraries are available, as described below.

If you don't find support for the type you're looking for, implementing your own delegate in your own project based on the code of existing delegates should be quite simple, this is very much a supported use case. If you think your type might be commonly used, you can also open an issue to ask for an addon library to provide for that type.

krate-gson

krate-gson provides you a gsonPref delegate which can store any arbitrary type, as long as GSON can serialize and deserialize it. This addon, like the base library, is available from mavenCentral():

implementation 'hu.autsoft:krate-gson:0.1.2'

Its basic usage is the same as with any of the base library's delegates:

class GsonKrate(context: Context) : SimpleKrate(context) {
    var user: User? by gsonPref("user")
    var savedArticles: List<Article>? by gsonPref("articles")
}

By default, the Gson instance created by a simple Gson() constructor call is used. If you want to provide your own Gson instance that you've configured, you can set the gson extension property on your Krate. Any gsonPref delegates within this Krate will use this instance for serialization and deserialization.

class CustomGsonKrate(context: Context) : SimpleKrate(context) {
    init {
        gson = GsonBuilder().create()
    }
}

License

Copyright 2019 AutSoft

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

kevincianfarini / Krate