Android’s SharedPreferences offers a convenient mechanism to persist a collection of key-value pairs.
It’s simplistic API makes it limiting for a few reasons:
Callers must always know the preference key and type.
No support for storing custom types out of the box.
Callers cannot listen for changes to individual keys.
RxPreferences is a new(ish) library that builds on top of SharedPreferences to solve these problems, and takes it further by integrating with RxJava.
SharedPreferences requires callers to always know what key identifies a preference when they get or save a preference. Callers also need to keep track of what type was used for a preference (did the preference use a float or int), which can lead to subtle bugs.
RxPreferences introduces a Preference class, that identifies key used to store it and the type of data it holds, making it easier to spot such bugs at compile time. RxSharedPreferences provides factory methods to promote preferences to objects.
The Preference class provides methods that replace their counterparts in SharedPreferences and SharedPreferences.Editor. This makes it convenient to use them as the source of truth, instead of sharing String constants throughout your app.
SharedPreferences restricts you to a set of limited types — boolean, float, int, long, String and Set<String>. Trying to persist custom types is doable, but looks awkward.
RxPreferences introduces a pluggable Adapter abstraction. An Adapter can store and retrieve values of an arbitrary type, and consolidates your serialization logic into a single location.
RxPreferences provides built in adapters for all the types suppored by SharedPreferences and enums. Writing a custom adapter is trivial. You can even use your own favorite serialization library!
Then, simply let RxPreferences know which adapter you want to use.
The Preference class integrates with RxJava, and lets you observe changes to a single preference directly. Internally, RxPreferences shares a single listener amongst all Preference objects to avoid unnecessary work.
RxPreferences also lets you take actions on preferences to update or delete values. This makes it straightforward to set up complex pipelines by combining it with other libraries in the RxJava family.
For example, RxPreferences and RxBinding can be combined to hand roll your own simplified CheckBoxPreference.
RxPreferences makes it convenient to interact with SharedPreferences, and integrating with RxJava makes it easy to express complex logic that would otherwise have been tedious and brittle. RxPreferences is available on Maven Central. Check the Github repo or u2020 to see more examples.