#281 fix bug in ListTransformation

mvvmfx/src/main/java/de/saxsys/mvvmfx/utils/itemlist/ListTransformation.java

@@ -89,6 +89,7 @@ public void onChanged(
 				// targetList
 				List<TargetType> deleteStaging = new ArrayList<>();
 
+
 				while (listEvent.next()) {
 					if (listEvent.wasUpdated()) {
 						processUpdateEvent(listEvent);
@@ -118,10 +119,13 @@ public void onChanged(
 	 */
 	private void processAddEvent(
 			ListChangeListener.Change<? extends SourceType> listEvent) {
-		for (int i = listEvent.getFrom(); i < listEvent.getTo(); i++) {
-			SourceType item = listEvent.getList().get(i);
-			viewModelList.add(i, ListTransformation.this.function.apply(item));
+
+		final List<TargetType> toAdd = new ArrayList<>();
+		for (int index = listEvent.getFrom(); index < listEvent.getTo(); index++) {
+			final SourceType item = listEvent.getList().get(index);
+			toAdd.add(function.apply(item));
 		}
+		viewModelList.addAll(listEvent.getFrom(), toAdd);
 	}
 
 	/**

mvvmfx/src/test/java/de/saxsys/mvvmfx/utils/itemlist/ItemListTest.java

@@ -16,12 +16,19 @@
 package de.saxsys.mvvmfx.utils.itemlist;
 
 import javafx.collections.FXCollections;
+import javafx.collections.ListChangeListener;
 import javafx.collections.ObservableList;
 
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * Tests for {@link ItemList}.
  * 
@@ -143,5 +150,36 @@ public void replaceItemInItemListAtIndex() {
 		Assert.assertEquals(PREFIX + "replacedPerson", itemList
 				.stringListProperty().get(1));
 	}
-
+
+	/**
+	 * This test is used to reproduce the bug <a href="https://github.com/sialcasa/mvvmFX/issues/281">#281</a>.
+	 * 
+	 * When multiple elements are added to the list in a single method call ({@link ObservableList#addAll(Object[])},
+	 * only a single change event should be fired.
+	 */
+	@Test
+	public void addMultipleItemsEventListener() {
+		AtomicInteger counter = new AtomicInteger(0);
+
+		itemList.getTargetList().addListener((ListChangeListener<String>) c -> {
+			counter.incrementAndGet();
+		});
+
+		listWithModelObjects.addAll(new Person("one"), new Person("two"), new Person("three"));
+
+		assertThat(counter.get()).isEqualTo(1);
+	}
+
+	@Test
+	public void removeMultipleItemsEventListener() {
+		AtomicInteger counter = new AtomicInteger(0);
+
+		itemList.getTargetList().addListener((ListChangeListener<String>) c -> {
+			counter.incrementAndGet();
+		});
+
+		listWithModelObjects.removeAll(person1, person3);
+
+		assertThat(counter.get()).isEqualTo(1);
+	}
 }