Question

I am creating a universal chat application using JavaFX. I created a listView using SceneBuilder and modeled it with ObservableList like below:

public static ObservableList<String>  members = FXCollections.observableArrayList();

@FXML public static Button send;
@FXML static  ListView names;
@FXML static HTMLEditor outmsg;
@FXML static HTMLEditor showBox;

static void updateRemove(String newuser) {

 //   showBox.setHtmlText(showBox.getHtmlText()+newuser+"<br>  has left room");
    System.out.println(newuser+"has left room");
    members.remove(newuser);
    System.out.println("helloji update remove");


}
@FXML public void sendAction(ActionEvent event)
{


 LoginController.instance.c.sendMessage(outmsg.getHtmlText());


}
public  static void updateList(String name)
{
   // showBox.setHtmlText(showBox.getHtmlText()+"<br> new user entered in room");
    System.out.println("new user enterd"+name);
    System.out.println("beginning update list");
    members.add(name);
    System.out.println(members);
    System.out.println("add user request fullfilled");


}
 public  static void initList(Vector<String> name)
{
    System.out.println("list initializing");
    members.setAll(name);
      System.out.println(members);
    System.out.println("list initialized");

    System.out.println("public room created");


}
public static void showMessage(String msg)
{

   // showBox.setHtmlText(showBox.getHtmlText()+""+msg);
        System.out.println("showing msg   "+msg);
}

@Override
public void initialize(URL url, ResourceBundle rb) {
    // TODO



     names.setItems(members);
    // showBox.setHtmlText(showBox.getHtmlText()+"<br> welcome "+Client.username);
         System.out.println("welcome  "+Client.username);

     System.out.println(names.getItems());

}    

}

but when its updateRemove() method is called, exception is thrown:

java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-4
    at com.sun.javafx.tk.Toolkit.checkFxUserThread(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(Unknown Source)
    at javafx.scene.Parent$1.onProposedChange(Unknown Source)
    at com.sun.javafx.collections.VetoableObservableList.setAll(Unknown Source)
    at com.sun.javafx.collections.ObservableListWrapper.setAll(Unknown Source)
    at com.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(Unknown Source)
    at com.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(Unknown Source)
    at com.sun.javafx.scene.control.skin.SkinBase$4.changed(Unknown Source)
    at javafx.beans.value.WeakChangeListener.changed(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(Unknown Source)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(Unknown Source)
    at javafx.beans.property.StringPropertyBase.fireValueChangedEvent(Unknown Source)
    at javafx.beans.property.StringPropertyBase.markInvalid(Unknown Source)
    at javafx.beans.property.StringPropertyBase.set(Unknown Source)
    at javafx.beans.property.StringPropertyBase.set(Unknown Source)
    at javafx.beans.property.StringProperty.setValue(Unknown Source)
    at javafx.scene.control.Labeled.setText(Unknown Source)
    at com.sun.javafx.scene.control.skin.ListViewSkin$12.updateItem(Unknown Source)
    at javafx.scene.control.ListCell.updateItem(Unknown Source)
    at javafx.scene.control.ListCell.access$000(Unknown Source)
    at javafx.scene.control.ListCell$5.onChanged(Unknown Source)
    at com.sun.javafx.scene.control.WeakListChangeListener.onChanged(Unknown Source)
    at com.sun.javafx.collections.ObservableListWrapper.callObservers(Unknown Source)
    at com.sun.javafx.collections.ObservableListWrapper.remove(Unknown Source)
    at com.sun.javafx.collections.ObservableListWrapper.remove(Unknown Source)
    at truechatter.RoomController.updateRemove(RoomController.java:45)
    at truechatter.Client.run(Client.java:78)

while initList() method works properly. Why?

Answer 1

The UI can only be updated by the gui-thread.

Use:

// create JavaFX scene
Platform.runLater(new Runnable() {
    public void run() {
        members.add(name);
    }
});

why the initialize() method works is probably because it is already invoked from FX application thread

from javadoc link:

public static void runLater(java.lang.Runnable runnable)

Run the specified Runnable on the JavaFX Application Thread at some
unspecified time in the future. This method, which may be called from
any thread, will post the Runnable to an event queue and then return
immediately to the caller. The Runnables are executed in the order
they are posted. A runnable passed into the runLater method will be
executed before any Runnable passed into a subsequent call to
runLater.