Concatenate Javafx fx:Id

Question

I\'m kinda new to JavaFX and currently trying to do a Calendar application for a school project. I was wondering if there was a way to concatenate a fx:id

Answer 1

Various possible solutions:

1. You could use reflection, but that would be ugly and I wouldn't advise it.

2. Normally, if you have a lot of things, you put them in a collection like a list or array. The label will be a child of some layout pane, so you can get the children of the pane and lookup an item by index with something like:

   ((Label) parent.getChildren().get(0)).setText("Text");
   

3. If the label has been assigned a css id then you can use that to lookup the label.

   For example, in your FXML define:

   <Label text="hello" fx:id="Box01" id="Box01"/>
   

   Then you can lookup the label using:

   String boxNum = "01";
   Label box = (Label) parent.lookup("#Box" + boxNum);
   

4. Just refer to the item by it's reference:

   @FXML private Label box01; 
   box01.setText("Test");
   

Aside: Please use camel case as per standard Java conventions.

Answer 2

In addition to the methods mentioned by @jewelsea here are 2 more ways to do this:

1. Create & inject a Map containing the boxes as values from the fxml:

   <VBox xmlns:fx="http://javafx.com/fxml/1" fx:controller="fxml.Controller">
       <children>
           <Label text="foo" fx:id="a"/>
           <Label text="bar" fx:id="b"/>
           <Spinner fx:id="number">
               <valueFactory>
                   <SpinnerValueFactory.IntegerSpinnerValueFactory min="1" max="2"/>
               </valueFactory>
           </Spinner>
           <Button text="modify" onAction="#modify"/>
           <fx:define>
               <HashMap fx:id="boxes">
                   <box1>
                       <fx:reference source="a"/>
                   </box1>
                   <box2>
                       <fx:reference source="b"/>
                   </box2>
               </HashMap>
           </fx:define>
       </children>
   </VBox>
   

   Controller

   public class Controller {
   
       private Map<String, Label> boxes;
       @FXML
       private Spinner<Integer> number;
       @FXML
       private Label box1;
       @FXML
       private Label box2;
   
       @FXML
       private void modify(ActionEvent event) {
           boxes.get("box"+number.getValue()).setText("42");
       }
   
   }
   

2. Pass the namespace of the FXMLLoader, which is a Map<String, Object> mapping fx:ids to the associated Objects, to the controller:

   <VBox xmlns:fx="http://javafx.com/fxml/1" fx:controller="fxml.Controller">
       <children>
           <Label text="foo" fx:id="box1"/>
           <Label text="bar" fx:id="box2"/>
           <Spinner fx:id="number">
               <valueFactory>
                   <SpinnerValueFactory.IntegerSpinnerValueFactory min="1" max="2"/>
               </valueFactory>
           </Spinner>
           <Button text="modify" onAction="#modify"/>
       </children>
   </VBox>
   

   Controller

   public class Controller implements NamespaceReceiver {
   
       private Map<String, Object> namespace;
       @FXML
       private Spinner<Integer> number;
       @FXML
       private Label box1;
       @FXML
       private Label box2;
   
       @FXML
       private void modify(ActionEvent event) {
           ((Label)namespace.get("box" + number.getValue())).setText("42");
       }
   
       @Override
       public void setNamespace(Map<String, Object> namespace) {
           this.namespace = namespace;
       }
   }
   

   public interface NamespaceReceiver {
       public void setNamespace(Map<String, Object> namespace);
   }
   

   Code for loading the fxml:

   public static <T> T load(URL url) throws IOException {
       FXMLLoader loader = new FXMLLoader(url);
       T result = loader.load();
       Object controller = loader.getController();
       if (controller instanceof NamespaceReceiver) {
           ((NamespaceReceiver) controller).setNamespace(loader.getNamespace());
       }
       return result;
   }