Created interface 'ListenerHandle' (still undocumented).

Author: nicolaiparlog

src/main/java/org/codefx/libfx/listener/ListenerHandle.java

@@ -0,0 +1,12 @@
+package org.codefx.libfx.listener;
+
+// TODO what should the contract be for created handles? Always attached?
+// Answer: Up to the returning method to specify!
+
+public interface ListenerHandle {
+
+	void attach();
+
+	void detach();
+
+}

src/test/java/org/codefx/libfx/listener/CreateListenerHandle.java

@@ -0,0 +1,18 @@
+package org.codefx.libfx.listener;
+
+/**
+ * Indicates how to create the {@link ListenerHandle}. If the handle is created by a builder, the corresponding method
+ * should be called (in order to test it) instead of attaching/detaching the listener after its creation.
+ */
+public enum CreateListenerHandle {
+
+	/**
+	 * The listener must be initially attached.
+	 */
+	ATTACHED,
+
+	/**
+	 * The listener must be initially detached.
+	 */
+	DETACHED;
+}