title: Add expand animation to TreeView
body: <p>I have this example of TreeView:</p>
  
  <p><img src="https://i.stack.imgur.com/SnKMP.png" alt="enter image description here"></p>
  
  <pre><code>import java.util.Arrays;
  import java.util.List;
  import javafx.application.Application;
  import javafx.beans.property.SimpleStringProperty;
  import javafx.event.EventHandler;
  import javafx.scene.Scene;
  import javafx.scene.control.TextField;
  import javafx.scene.control.TreeCell;
  import javafx.scene.control.TreeItem;
  import javafx.scene.control.TreeView;
  import javafx.scene.input.KeyCode;
  import javafx.scene.input.KeyEvent;
  import javafx.scene.layout.VBox;
  import javafx.scene.paint.Color;
  import javafx.stage.Stage;
  import javafx.util.Callback;
  
  public class MainApp extends Application
  {
  
      //private final Node rootIcon = new ImageView(new Image(getClass().getResourceAsStream("picture.png")));
      //private final Image depIcon = new Image(getClass().getResourceAsStream("picture.png"));
      List&lt;Employee&gt; employees = Arrays.&lt;Employee&gt;asList(
          new Employee("Ethan Williams", "Sales Department"),
          new Employee("Emma Jones", "Sales Department"),
          new Employee("Michael Brown", "Sales Department"),
          new Employee("Anna Black", "Sales Department"),
          new Employee("Rodger York", "Sales Department"),
          new Employee("Susan Collins", "Sales Department"),
          new Employee("Mike Graham", "IT Support"),
          new Employee("Judy Mayer", "IT Support"),
          new Employee("Gregory Smith", "IT Support"),
          new Employee("Jacob Smith", "Accounts Department"),
          new Employee("Isabella Johnson", "Accounts Department"));
      TreeItem&lt;String&gt; rootNode = new TreeItem&lt;&gt;("MyCompany Human Resources");//, rootIcon);    // Set picture
  
      public static void main(String[] args)
      {
          Application.launch(args);
      }
  
      @Override
      public void start(Stage stage)
      {
          rootNode.setExpanded(true);
          for (Employee employee : employees)
          {
              TreeItem&lt;String&gt; empLeaf = new TreeItem&lt;&gt;(employee.getName());
              boolean found = false;
              for (TreeItem&lt;String&gt; depNode : rootNode.getChildren())
              {
                  if (depNode.getValue().contentEquals(employee.getDepartment()))
                  {
                      depNode.getChildren().add(empLeaf);
                      found = true;
                      break;
                  }
              }
              if (!found)
              {
                  TreeItem&lt;String&gt; depNode = new TreeItem&lt;&gt;(
                      employee.getDepartment()//,new ImageView(depIcon)   // Set picture
                  );
                  rootNode.getChildren().add(depNode);
                  depNode.getChildren().add(empLeaf);
              }
          }
  
          stage.setTitle("Tree View Sample");
          VBox box = new VBox();
          final Scene scene = new Scene(box, 400, 300);
          scene.setFill(Color.LIGHTGRAY);
  
          TreeView&lt;String&gt; treeView = new TreeView&lt;&gt;(rootNode);
          //treeView.setEditable(true);
          treeView.setCellFactory(new Callback&lt;TreeView&lt;String&gt;, TreeCell&lt;String&gt;&gt;()
          {
              @Override
              public TreeCell&lt;String&gt; call(TreeView&lt;String&gt; p)
              {
                  return new TextFieldTreeCellImpl();
              }
          });
  
          box.getChildren().add(treeView);
          stage.setScene(scene);
          stage.show();
      }
  
      private final class TextFieldTreeCellImpl extends TreeCell&lt;String&gt;
      {
  
          private TextField textField;
  
          public TextFieldTreeCellImpl()
          {
          }
  
          @Override
          public void startEdit()
          {
              super.startEdit();
  
              if (textField == null)
              {
                  createTextField();
              }
              setText(null);
              setGraphic(textField);
              textField.selectAll();
          }
  
          @Override
          public void cancelEdit()
          {
              super.cancelEdit();
              setText((String) getItem());
              setGraphic(getTreeItem().getGraphic());
          }
  
          @Override
          public void updateItem(String item, boolean empty)
          {
              super.updateItem(item, empty);
  
              if (empty)
              {
                  setText(null);
                  setGraphic(null);
              }
              else
              {
                  if (isEditing())
                  {
                      if (textField != null)
                      {
                          textField.setText(getString());
                      }
                      setText(null);
                      setGraphic(textField);
                  }
                  else
                  {
                      setText(getString());
                      setGraphic(getTreeItem().getGraphic());
                  }
              }
          }
  
          private void createTextField()
          {
              textField = new TextField(getString());
              textField.setOnKeyReleased(new EventHandler&lt;KeyEvent&gt;()
              {
  
                  @Override
                  public void handle(KeyEvent t)
                  {
                      if (t.getCode() == KeyCode.ENTER)
                      {
                          commitEdit(textField.getText());
                      }
                      else if (t.getCode() == KeyCode.ESCAPE)
                      {
                          cancelEdit();
                      }
                  }
              });
          }
  
          private String getString()
          {
              return getItem() == null ? "" : getItem().toString();
          }
      }
  
      public static class Employee
      {
  
          private final SimpleStringProperty name;
          private final SimpleStringProperty department;
  
          private Employee(String name, String department)
          {
              this.name = new SimpleStringProperty(name);
              this.department = new SimpleStringProperty(department);
          }
  
          public String getName()
          {
              return name.get();
          }
  
          public void setName(String fName)
          {
              name.set(fName);
          }
  
          public String getDepartment()
          {
              return department.get();
          }
  
          public void setDepartment(String fName)
          {
              department.set(fName);
          }
      }
  }
  </code></pre>
  
  <p>I want to add animation when I expand the tree. How this can be done?</p>