use collect in ListenersTrait instead of filter and map

addon/src/main/scala/vaadin/scala/internal/ListenersTrait.scala

@@ -10,15 +10,15 @@ trait ListenersTrait[E, L <: Listener] extends mutable.Set[E => Unit] with Liste
     iterator.contains(key)
   }
   def iterator(): Iterator[E => Unit] = {
-    val list = listeners.asScala.filter(_.isInstanceOf[L]).map(_.asInstanceOf[L].action)
+    val list = listeners.asScala.collect { case l: L => l.action }
     list.iterator.asInstanceOf[Iterator[E => Unit]]
   }
   def +=(elem: => Unit) = { addListener((e: E) => elem); this }
   def +=(elem: E => Unit) = { addListener(elem); this }
   def -=(elem: E => Unit) = {
-    val list = listeners.asScala.filter(_.isInstanceOf[L]).foreach { e =>
-      if (e.asInstanceOf[L].action == elem) {
-        removeListener(e.asInstanceOf[L])
+    val list = listeners.asScala.collect { case l: L =>
+      if (l.action == elem) {
+        removeListener(l)
         this
       }
     }

addon/src/test/scala/vaadin/scala/tests/ListenersTraitTests.scala

@@ -0,0 +1,36 @@
+package vaadin.scala.tests
+
+import com.vaadin.ui.Button.{ClickEvent, ClickListener}
+import vaadin.scala._
+
+/**
+ *
+ * @author Henri Kerola / Vaadin
+ */
+class ListenersTraitTests extends ScaladinTestSuite {
+
+  test("iterator") {
+    val button = new Button
+
+    button.clickListeners += { e => }
+
+    button.p.addClickListener(new ClickListener {
+      override def buttonClick(clickEvent: ClickEvent): Unit = {}
+    })
+
+    assert(1 == button.clickListeners.size)
+    assert(2 == button.p.getListeners(classOf[com.vaadin.ui.Button.ClickEvent]).size)
+  }
+
+  test("-=") {
+    val button = new Button
+
+    val clickListener = { e: Button.ClickEvent => }
+    button.clickListeners += clickListener
+    assert(1 == button.clickListeners.size)
+
+    button.clickListeners -= clickListener
+    assert(0 == button.clickListeners.size)
+  }
+
+}