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Dynamically adding JavaFX controls

Dynamically adding JavaFX controls

The JavaFX SceneBuilder works very well for constructing a static GUI; that is, a GUI whose controls are determined entirely at compile-time.  But sometimes it is useful to be able to add new controls dynamically at run-time.  The example below demonstrates one way to do this.

In this example, the user creates Button objects on-the-fly.  They are displayed using a ListViewer and stored in an ObservableList.  Each button inverts the capitalization of its label when clicked.  The Controller class is given below; constructing the rest of the GUI is an exercise for the reader.

package application;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.ListView;
import javafx.scene.control.TextField;
import javafx.scene.input.MouseEvent;

public class Controller {
 @FXML
 private Button add;
 @FXML 
 private TextField button;
 @FXML 
 private ListView<Button> visibleList;
 
 private ObservableList<Button> buttons = 
 FXCollections.observableArrayList();
 
 @FXML
 protected void initialize() {
 visibleList.setItems(buttons);
 }
 
 @FXML
 void addName() {
 Button b = new Button(button.getText());
 buttons.add(b);
 b.addEventHandler(MouseEvent.MOUSE_CLICKED, 
 (event -> b.setText(invertCapitals(b.getText()))));
 button.setText("");
 }
 
 public static String invertCapitals(String other) {
 return other.chars().mapToObj(Controller::flipCap)
 .map(c -> Character.toString(c))
 .reduce("", (s, c) -> s + c);
 }
 
 public static Character flipCap(int c) {
 if (c >= A && c <= Z) {
 return (char)(c - A + a);
 } else if (c >= a && c <= z) {
 return (char)(c - a + A);
 } else {
 return (char)c;
 }
 }
}

Highlighted in red, the key to making this all work is the addName() method, working in combination with the ObservableList buttons.   This method creates a new Button object in response to every click of the add button.  This object is added to our ObservableList, which makes it visible in the ListViewer.  Finally, we employ a Java 8 lambda to implement the event handler.

There is a pretty long list of event types to which one might respond.  Check out the documentation for the MouseEvent and KeyEvent classes to get started.

Heres a sample run of the program:


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