ComboBox 显示空列表

Question

I am trying to use different objects at JavaFX and stacked on combobox. It shows list without elements.

public class Controller extends Application {

public void start(Stage primaryStage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
    primaryStage.setTitle("Hello World");
    primaryStage.setScene(new Scene(root, 300, 275));
    primaryStage.show();

}

public Label label1 = new Label();
public CheckBox cbox1 = new CheckBox();
public ObservableList<String> options = FXCollections.observableArrayList(
         "Option 1",
                "Option 2",
                "Option 3"
        );

public ComboBox comboBox = new ComboBox(options);
......
<ComboBox id="comboBox" fx:id="comboBox" prefWidth="150.0" 
GridPane.columnIndex="1" GridPane.rowIndex="11" />
......

Answer 1

You are not adding the ComboBox from your FXML into your Controller . Instead, you are creating a brand new ComboBox (which is not being displayed in your scene).

You should remove this line:

public ComboBox comboBox = new ComboBox(options);

And replace it with this:

@FXML
private ComboBox comboBox;

Then it's just a matter of setting the items for the combobox:

comboBox.setItems(options);

---

Why? The @FXML annotation tells JavaFX that the ComboBox you refer to on the following line has been defined in your FXML file. This allows JavaFX to "inject" that object into your controller.

Side Note: It is generally not a good idea to use your main class as your controller class (I recommend creating a separate controller class for your FXML). Your controller class should also include a private void initialize() method (annotated with @FXML ). This is where you can setup the parameters for your scene's controls. Most introductory JavaFX tutorials will walk you through that process.