JavaFx: TreeTableView weird NullpointerException

Sunflame :

I have noticed a weird NPE in the TreeTableView

It happens if you doubleClick in the table where there is no row present. Ill attach a screenshot to show what I mean exactly.

I comes purely from JavaFx it has nothing to do with my code. I also did a research and didn't find anything related to this.

Here is a simple code to reproduce it:

Controller:

public class Controller implements Initializable {
    @FXML
    private TreeTableColumn<Model, String> column;
    @FXML
    private TreeTableView<Model> treeTable;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        TreeItem<Model> root = new TreeItem<>(new Model("Root"));
        treeTable.setRoot(root);
        column.setCellValueFactory(value -> value.getValue().getValue().textProperty());

    }

    private class Model {
        private StringProperty text;

        Model(String text) {
            this.text = new SimpleStringProperty(text);
        }

        public StringProperty textProperty() {
            return text;
        }

        public String getText() {
            return text.get();
        }

        @Override
        public String toString() {
            return getText();
        }
    }
}

.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.TreeTableColumn?>
<?import javafx.scene.control.TreeTableView?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane xmlns="http://javafx.com/javafx"
            xmlns:fx="http://javafx.com/fxml"
            fx:controller="stackoverflow.treeview.Controller">
    <TreeTableView fx:id="treeTable">
        <columns>
            <TreeTableColumn fx:id="column" text="Test"/>
        </columns>
    </TreeTableView>
</AnchorPane>

If you double click in the red region a NPE is thrown.

Stacktrace:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at com.sun.javafx.scene.control.behavior.TreeTableRowBehavior.handleClicks(TreeTableRowBehavior.java:89)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.simpleSelect(CellBehaviorBase.java:259)
    at com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.doSelect(TableRowBehaviorBase.java:120)
    at com.sun.javafx.scene.control.behavior.CellBehaviorBase.mousePressed(CellBehaviorBase.java:150)
    at com.sun.javafx.scene.control.behavior.TableRowBehaviorBase.mousePressed(TableRowBehaviorBase.java:64)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:95)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

Java version: 1.8u121

As a solution I would accept any workaround which really works or any explanation/javafx bug-report which shows they are working on it or there is a fix in a following version.

Slaw :

When you click in the empty space, where there's no columns, you end up clicking on a TreeTableRow. Apparently there is a bug in the control's behavior class that means it can't handle rows with null items. You don't see this bug if you click in the empty space of a column because that clicks on a TreeTableCell, whose behavior class does not seem to suffer from the same problem. Not sure where the exact difference is, but I only quickly glanced at the source code.

One way to stop the exception being thrown, as @kleopatra mentioned, is to add an event filter to the TreeTableRow that consumes double clicks on empty rows.

var table = new TreeTableView<String>();
table.setRowFactory(ttv -> {
    var row = new TreeTableRow<String>();
    row.addEventFilter(MouseEvent.MOUSE_PRESSED, event -> {
        if (row.getItem() == null && event.getClickCount() % 2 == 0) {
            event.consume();
        }
    });
    return row;
});

Note: You need clickCount % 2 == 0 because the behavior class will try to access the TreeItem when the click count is even.