Implement fromObservableValueChanges

src/main/java/rx/javafx/sources/Change.java

@@ -0,0 +1,17 @@
+package rx.javafx.sources;
+
+public final class Change<T> {
+    private final T oldVal;
+    private final T newVal;
+
+    public Change(T oldVal, T newVal) {
+        this.oldVal = oldVal;
+        this.newVal = newVal;
+    }
+    public T getOldVal() {
+        return oldVal;
+    }
+    public T getNewVal() {
+        return newVal;
+    }
+}

src/main/java/rx/javafx/sources/ObservableValueSource.java

@@ -4,7 +4,6 @@
 import javafx.beans.value.ObservableValue;
 import rx.Observable;
 import rx.Subscriber;
-import rx.functions.Action0;
 import rx.subscriptions.JavaFxSubscriptions;
 
 public class ObservableValueSource {
@@ -18,25 +17,31 @@ public static <T> Observable<T> fromObservableValue(final ObservableValue<T> fxO
             public void call(final Subscriber<? super T> subscriber) {
                 subscriber.onNext(fxObservable.getValue());
 
-                final ChangeListener<T> listener = new ChangeListener<T>() {
-                    @Override
-                    public void changed(final ObservableValue<? extends T> observableValue, final T prev, final T current) {
-                        subscriber.onNext(current);
-                    }
-                };
+                final ChangeListener<T> listener = (observableValue, prev, current) -> subscriber.onNext(current);
 
                 fxObservable.addListener(listener);
 
-                subscriber.add(JavaFxSubscriptions.unsubscribeInEventDispatchThread(new Action0() {
-                    @Override
-                    public void call() {
-                        fxObservable.removeListener(listener);
-                    }
-                }));
+                subscriber.add(JavaFxSubscriptions.unsubscribeInEventDispatchThread(() -> fxObservable.removeListener(listener)));
 
             }
         });
     }
+    /**
+     * @see rx.observables.JavaFxObservable#fromObservableValue
+     */
+    public static <T> Observable<Change<T>> fromObservableValueChanges(final ObservableValue<T> fxObservable) {
+        return Observable.create(new Observable.OnSubscribe<Change<T>>() {
+            @Override
+            public void call(final Subscriber<? super Change<T>> subscriber) {
+
+                final ChangeListener<T> listener = (observableValue, prev, current) -> subscriber.onNext(new Change<>(prev,current));
 
+                fxObservable.addListener(listener);
+
+                subscriber.add(JavaFxSubscriptions.unsubscribeInEventDispatchThread(() -> fxObservable.removeListener(listener)));
+
+            }
+        });
+    }
 
 }

src/main/java/rx/observables/JavaFxObservable.java

@@ -21,6 +21,7 @@
 import javafx.event.EventType;
 import javafx.scene.Node;
 import rx.Observable;
+import rx.javafx.sources.Change;
 import rx.javafx.sources.NodeEventSource;
 import rx.javafx.sources.ObservableValueSource;
 
@@ -50,4 +51,15 @@ public static <T extends Event> Observable<T> fromNodeEvents(final Node node, fi
     public static <T> Observable<T> fromObservableValue(final ObservableValue<T> fxObservable) {
         return ObservableValueSource.fromObservableValue(fxObservable);
     }
+
+    /**
+     * Create an rx Observable from a javafx ObservableValue, and emits changes with old and new value pairs
+     *
+     * @param fxObservable the observed ObservableValue
+     * @param <T>          the type of the observed value
+     * @return an Observable emitting values as the wrapped ObservableValue changes
+     */
+    public static <T> Observable<Change<T>> fromObservableValueChanges(final ObservableValue<T> fxObservable) {
+        return ObservableValueSource.fromObservableValueChanges(fxObservable);
+    }
 }