Adding dynamic entries to Menu in JavaFX

问题

I'm trying to dynamically add entries to a JavaFX menu. I have a program that can draw graphs, each time a new graph is drawn, I add an entry to the an ObservableList with all graphs.
My controller observes the list and on each change, it should modify the Menu in the JavaFX view. However I'm running in a problem when doing so.
On the first add, it shows as expected the first entry.
On the second add, the list contains the first entry + the first entry + the last entry.
On the third add it shows the first entry + the first entry + the second entry + the first entry + the second entry + the last entry. I guess you can guess the pattern from this point forward.
This code snippet is taken from my controller:

graphHandler.getGraphs().addListener(new ListChangeListener<Graph>() {
//GraphHandler.class is my model, that holds the list with all graphs
    @Override
    public void onChanged(Change<? extends Graph> c) {
        Menu history = graphView.getHistoryMenu();
        history.getItems().removeAll();
        //on change get the Menu from the model and empty it
        String changes = (String) c.toString();
        System.out.println(changes);
        //Output will be added below snippet
        graphHandler.getGraphs().forEach((Graph graph) -> {
            String root = graph.getRootNode().toString();
            MenuItem item = new MenuItem(root);
            //Get the graph's root node name and add a MenuItem with it's name
            item.setOnAction(new EventHandler<ActionEvent>() {
            //On choosing a MenuItem load the according graph; works fine
                @Override
                public void handle(ActionEvent event) {
                    graphHandler.getGraphByRootNode(root);
                }
            });
            history.getItems().addAll(item);
            //Add all MenuItems to the Menu
        });
    }
});

My approach was to empty the Menu on every change and refill it, but it doesn't seem to work. Does anybody have an Idea what I'm missing?

{ [com.example.d3project.model.Graph@7eb5106] added at 0 }
{ [com.example.d3project.model.Graph@f510ff2] added at 1 }
{ [com.example.d3project.model.Graph@69239a8d] added at 2 }

The output shows what I'm expecting to see. Also the size() of the ObservableList is as I'm expecting it.

回答1:

You are using removeAll(E...) where you need to pass the objects you want to remove. Since you don't pass any argument nothing will be removed. To clear the list use clear() which will remove all items in your history list.

来源：https://stackoverflow.com/questions/36149474/adding-dynamic-entries-to-menu-in-javafx

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javafx

menuitem