KPreferences
A Kotlin library for reactive and boilerplate-free Shared Preferences in Android. With KPreferences you can use Kotlin's marvelous delegate concept to easily use Android's Shared Preferences. Features:
- Boilerplate-free: Use
SharedPreferences
properties with one line and withoutedit
,apply
or ... boilerplate codes - Reactive: Use observables to listen for
SharedPreferences
changes without any memory leak - Custom types: You are not limited to a set of limited types that can be saved to the
SharedPreferences
.
If you have any issues or need more features, you can submit an issue in the issue tracker or make a pull request.
Importing
Add this line to your module's build.gradle
file:
dependencies {
compile 'com.mohamadamin.kpreferences:kpreferences:0.1'
}
Usage
First you need to initialize KPreferenceManager
in your application class. You can also provide name
of the SharedPreference
and mode
for the operating mode but it's not needed (defaults to "default"
for file name and Context.MODE_PRIVATE
for mood):
override fun onCreate() {
super.onCreate()
KPreferenceManager.initialize(this)
}
Use SharedPreferences
in your project with only one line:
val intPreference: Int by Preference(-1, "IntPreference")
it creates a SharedPreferences
property with IntPreference
name and -1
as its default value.
Then the intPreference
property is automatically saved when you change the intPreference
property and is directly retrieved from SharedPreferences
when you want to access its value:
// the age value is directly retrieved from SharedPreferences property named "IntPreference"
someClass.age = intPreference
// automatically is saved in shared preferences with no need to edit or ...
intPreference = 21
Reactive Preferences
KPreferences also provides Observable Preferences that lets you observe changes to a single preference. It uses SharedPreferences
's registerOnSharedPreferenceChangeListener
method.
But unlike that method that requires you to observe changes on all fields ObservablePreference
lets you only listen to the changes that you need:
// Composite destroyer to destroy all observables at once to avoid memory leaks
val destroyers = CompositeDestroyer()
var toolbarTitle: Int by ObservablePreference(
"ToolbarTitle", // SharedPreferences key
"Title", // SharedPreferences default value
subscriber = object: Subscriber<Int> { // observable for possible changes
override val subscriber: (Int) -> Unit
get() = {
// changing toolbar title when the preference is changed
setToolbarTitle("$it")
}
override fun setDestroyListener(callback: () -> Unit) {
// call this callback later to unregister the listener and avoid memory leaks
destroyers.add(callback)
}
}
)
but you need to destroy the destroyable callback
in your onDestroy
to avoid possible memory leaks. The CompositeDestroyer
is a helper class to destroy all callbacks at once:
override fun onDestroy() {
super.onDestroy()
destroyers.invoke()
}
Custom Types
You can use the adapter
abstraction to store and retrieve values of an arbitrary type.
As you see below you should override decode
and encode
functions of the Adapter<T>
class to create an adapter for the variable of type T
and save/restore it in SharedPreferences
. There's an example of an adapter which uses Gson to serialize/deserialize the custom type in the demo app.
/**
* @author MohamadAmin Mohamadi (mohammadi.mohamadamin@gmail.com) on 3/16/17.
* Converter for storing and retrieving objects of type [T] in [android.content.SharedPreferences]
*/
interface Adapter<T> {
/**
* Decode the string retrieved from [android.content.SharedPreferences] to an object of type [T]
* @param result the string retrieved from {@link SharedPreferences}
* @return the decoded object of type [T]
*/
fun decode(result: String): T?
/**
* Encode an object of type [T] to a string that can be saved in [android.content.SharedPreferences]
* @param value the object of type [T] that wants to be saved in [android.content.SharedPreferences]
* @return the encoded string from the input #value that can be saved in [android.content.SharedPreferences]
*/
fun encode(value: T): String
}
Demo
You can see a full demo of the library in the app module.
License
Copyright 2017 Mohamad Amin Mohamadi
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.