javafx choicebox to trigger a method onchange

Question

I am very rusty on my java and even more on javafx. so I got a choicebox "categoryDrop" that when the value of the choicebox change I want to trigger this event that then takes the value of the choicebox and compare to an object "Folder" categorylist which is an attribute it has.

here is my code

  @FXML 
private void folderByCategory(ActionEvent event) {
    System.out.println("här1");
      TreeItem<DocumentObject<?>> treeRoot = new TreeItem<>(new Folder());
    
    for (Folder folder : logic.getFolderList()) {
        
        if(f.getCategoryList().contains(categoryDrop.valueProperty())){
            System.out.println("här2");
          TreeItem<DocumentObject<?>> newFolders = new TreeItem<>(folder);
          
          for(FileReference file : folder.getFileList()){
            System.out.println(file.getName());
            TreeItem<DocumentObject<?>> fileNode = new TreeItem<>(file);
            newFolders.getChildren().add(fileNode);
        }
          
         treeRoot.getChildren().add(newFolders);
          treeRoot.setExpanded(true);
       }
        treeNav.setRoot(treeRoot);
    }
}

But then when I looked in scenebuilder I didn't see any good way to implement the method so it triggers when it changes. Anyone know a better way to do this? Should I use a listener instead maybe?

Answer 1

ChoiceBox has an onAction property, so in FXML you can simply assign this controller method to this property:

<ChoiceBox fx:id="categoryDrop" onAction="#folderByCategory" />

Unfortunately, the current version of Scene Builder does not support this property, so you cannot set this directly from Scene Builder. There is a current issue filed for this.

Some workarounds are:

1. Edit the FXML manually to add the onAction attribute, as above.
2. Use a ComboBox instead of a ChoiceBox. The functionality is similar (though not identical) and a ComboBox will likely do what you need. Scene Builder does support the onAction property of a ComboBox.

3. Register the handler in the controller's initialize() method instead. All you need is

   @FXML
   private ChoiceBox<...> categoryDrop ;
   
   public void initialize() {
       categoryDrop.setOnAction(this::folderByCategory);
       // existing code ...
   }
   
   @FXML
   private void folderByCategory(ActionEvent event) {
       // existing code...
   }