Rx2

The livedata library adds extension functions to convert the Prefrence into Observable and Consumer objects.

Getting the Dependency

implementation "com.frybits.rx.preferences:rx2:2.0.1"

Usage

Using non-nullable Preference with Rx2

Due to RxJava not allowing for null to be emitted, the asOptional() operator was created for Preference to convert any Preference<T> object into a Preference<Optional<T>> object. Note: This is the com.google.common.base.Optional class, and not the Java8 Optional class.

Kotlin Java

val rxSharedPreferences = sharedPreferences.asRxSharedPreferences()

val usernamePref: Preference<String?> = rxSharedPreferences.getString("username")
val optionalUsernamePref: Preference<Optional<String?>> = usernamePref.asOptional()

RxSharedPreferences rxSharedPreferences = RxSharedPreferences.create(sharedPreferences);

Preference<String> usernamePref = rxSharedPreferences.getString("username");
Preference<Optional<String>> optionalUsernamePref = PreferenceUtil.asOptional(usernamePref);

Preference as an Observable

Kotlin Java

val rxSharedPreferences = sharedPreferences.asRxSharedPreferences()

val usernamePref: Preference<String?> = rxSharedPreferences.getString("username", null)

// RxJava doesn't allow for 'null' values to be emitted. Make it optional instead.
val optionalUsernamePref: Preference<Optional<String?>> = usernamePref.asOptional()

val usernameObservable: Observable<Optional<String?>> = optionalUsernamePref.asObservable()

usernameObservable.subscribe { name ->
    println(name.orNull()) // Immediately emits an empty Optional
}

usernamePref.value = "bob"
// Output from RxJava => "bob"

// You could also set the value via the optional prefrence as such
optionalUsernamePref.value = Optional.fromNullable("foobar")
// Output from RxJava => "foobar"

// Or set it to null
usernamePref.value = null
// Output from RxJava => Empty optional

RxSharedPreferences rxSharedPreferences = RxSharedPreferences.create(sharedPreferences);

Preference<String> usernamePref = rxSharedPreferences.getString("username", null);

// RxJava doesn't allow for 'null' values to be emitted. Make it optional instead.
Preference<Optional<String>> optionalUsernamePref = PreferenceUtil.asOptional(usernamePref);

Observable<Optional<String>> usernameObservable = Rx2Preference.asObservable(optionalUsernamePref);

usernameObservable.subscribe(name -> {
    System.out.println(name.orNull()); // Immediately emits an empty Optional
});

usernamePref.setValue("bob");
// Output from RxJava => "bob"

// You could also set the value via the optional prefrence as such
optionalUsernamePref.setValue(Optional.fromNullable("foobar"));
// Output from RxJava => "foobar"

// Or set it to null
usernamePref.setValue(null);
// Output from RxJava => Empty optional

Preference as a Consumer

Kotlin Java

val rxSharedPreferences = sharedPreferences.asRxSharedPreferences()

val featureEnabledPref: Preference<Boolean> = rxSharedPreferences.getBoolean("somePref")

val featureEnabledConsumer = featureEnabledPref.asConsumer()

val checkButtonObservable = Observable.create { emitter ->

    val onChangedListener = OnCheckedChangeListener { _, isChecked ->
        emitter.onNext(isChecked)
    }

    emitter.setCancellable {
        button.setOnCheckedChangeListener(null)
    }

    button.setOnCheckedChangeListener(onChangedListener)
}

checkButtonObservable.subscribe(featureEnabledConsumer)

RxSharedPreferences rxSharedPreferences = RxSharedPreferences.create(sharedPreferences);

Preference<Boolean> featureEnabledPref = rxSharedPreferences.getBoolean("somePref");

Consumer<Boolean> featureEnabledConsumer = Rx2Preference.asConsumer(featureEnabledPref);

Observable<Boolean> checkButtonObservable = Observable.create(emitter -> {

    OnCheckedChangeListener onChangedListener = new OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            emitter.onNext(isChecked);
        }
    };

    emitter.setCancellable(() -> {
        button.setOnCheckedChangeListener(null);
    });

    button.setOnCheckedChangeListener(onChangedListener);
});

checkButtonObservable.subscribe(featureEnabledConsumer);