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  1. JDK
  2. JDK-8095096

toFront() throwing UnsupportedOperationException

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    • Bug
    • Resolution: Not an Issue
    • P4
    • 8u20
    • 8u20
    • javafx
    • None
    • Windows 7 x64

    Description

      I want to create a StackPane where, whatever is added, a node of my choice is always at the front (rather than having to be careful about the order I add things in, or remembering to call toFront() on that particular node whenever anything is added.)

      In order to do this, I simply place a listener on the child list of the relevant StackPane object, so that whenever anything changes, it calls toFront() on the relevant node, for example:



      public class Test extends Application {

          @Override
          public void start(Stage stage) {
              StackPane root = new StackPane();
              final Rectangle r1 = new Rectangle(50, 50);
              root.getChildren().add(r1);
              root.getChildren().addListener(new ListChangeListener<Node>() {
                  @Override
                  public void onChanged(ListChangeListener.Change<? extends Node> change) {
                      try {
                          while(change.next()) {
                              if(change.wasAdded()) {
                                  r1.toFront();
                              }
                          }
                      }
                      catch(Exception ex) {
                          ex.printStackTrace();
                      }
                  }
              });
              root.getChildren().add(new Rectangle(50, 50));

              stage.setScene(new Scene(root));
              stage.show();
          }
      }



      In JavaFX 2.2, this works just fine. However, in JFX8 (latest build downloaded just now), it fails with the following:

      java.lang.UnsupportedOperationException
              at java.util.Collections$UnmodifiableList.add(Collections.java:1374)
              at javafx.collections.ListChangeBuilder.nextRemove(ListChangeBuilder.java:208)
              at javafx.collections.ObservableListBase.nextRemove(ObservableListBase.java:150)
              at javafx.collections.ModifiableObservableListBase.remove(ModifiableObservableListBase.java:181)
              at com.sun.javafx.collections.VetoableListDecorator.remove(VetoableListDecorator.java:284)
              at com.sun.javafx.collections.VetoableListDecorator.remove(VetoableListDecorator.java:209)
              at javafx.scene.Parent.impl_toFront(Parent.java:624)
              at javafx.scene.Node.toFront(Node.java:1713)
              at test.Test$1.onChanged(Test.java:34)
              at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:315)
              at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:72)
              at com.sun.javafx.collections.VetoableListDecorator$1.onChanged(VetoableListDecorator.java:77)
              at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:315)
              at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:72)
              at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
              at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
              at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
              at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
              at javafx.collections.ModifiableObservableListBase.add(ModifiableObservableListBase.java:155)
              at java.util.AbstractList.add(AbstractList.java:108)
              at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:200)
              at test.Test.start(Test.java:41)
              at com.sun.javafx.application.LauncherImpl$8.run(LauncherImpl.java:837)
              at com.sun.javafx.application.PlatformImpl$7.run(PlatformImpl.java:331)
              at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:297)
              at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:294)
              at java.security.AccessController.doPrivileged(Native Method)
              at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:294)
              at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
              at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
              at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
              at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
              at java.lang.Thread.run(Thread.java:744)


      And yes, test.Test$1.onChanged(Test.java:34) does indeed refer to r1.toFront().

      I did wonder whether the list was still being changed while the onChanged() method was executing, and toFront() would also change the list contents, hence the exception - but the Javadoc to onChanged() clearly says:

      "Called **after** a change has been made to an ObservableList."

      ...so I see no reason in the documentation at least why that should prove an issue.

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              msladecek Martin Sládeček
              mberryjfx Michael Berry (Inactive)
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