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JavaFX tutorial part 2 - Creating a GUI for Duke

In this tutorial, we will be creating a GUI for Duke from scratch based on the following mockup.

JavaFX controls

Controls are reusable UI elements. Refer to the JavaFX's official documentation for a list of controls available. From the mockup above, can you identify the controls that we will need to use?

Mockup Control
ImageView
Label
Button
TextField
ScrollPane

Designing the Layout

Now that we know what controls we need to implement our UI, let’s start programming! We quickly run into a problem: how do we show all of them on the screen at once?

Each scene is initialized with a root Node. In the previous tutorial, our root Node was a Label. What happens when we need to display more than one Node on the Scene? For that, we need to understand the JavaFX hierarchy. Recall from the previous tutorial:

From the diagram, you see that the root Node can contain many other Nodes and similarly, each of those Nodes can contain many other Nodes. This means that if we can find a container to set as our root Node, we can place all our other Nodes in it.

But how do we get the exact layout we want in the UI? JavaFX provides that functionality in the form of layout panes in javafx.scene.layouts. Each layout pane follows a layout policy to decide how to arrange its children. For example, the VBox lays out its children in a single vertical column and its counterpart, the HBox lays out its children in a single horizontal row.

💡 A comprehensive list of layouts and how they behave is available here from the official documentation.

One way to obtain the layout in the mockup is as follows.

To get that layout, we create a new AnchorPane and add our controls to it. Similarly, we create a new VBox to hold the contents of the ScrollPane. The code should look something like this:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextField;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;


public class Duke extends Application {

    private ScrollPane scrollPane;
    private VBox dialogContainer;
    private TextField userInput;
    private Button sendButton;
    private Scene scene;

    public static void main(String[] args) {
        // ... 
    }

    @Override
    public void start(Stage stage) {
         //Step 1. Setting up required components
         
        //The container for the content of the chat to scroll.
         scrollPane = new ScrollPane();
         dialogContainer = new VBox();
         scrollPane.setContent(dialogContainer);

         userInput = new TextField();
         sendButton = new Button("Send");
     
         AnchorPane mainLayout = new AnchorPane();
         mainLayout.getChildren().addAll(scrollPane, userInput, sendButton);

         scene = new Scene(mainLayout);
     
         stage.setScene(scene);
         stage.show();

        // more code to be added here later
    }
}

Run the application and you should see something like this:

That is not what we were expecting, what did we forget to do?

Styling the Controls

Almost every JavaFX object offer properties that you can set to customize its look and feel. For example, the Stage allows you to set its preferred size and title. Again, refer to the official JavaFX documentation for a comprehensive list of properties that you can modify. Here’s how you can get the application to look like the mockup:

Add the following code to the bottom of the start method. You'll have to add import javafx.scene.layout.Region; to the imports too.

    @Override
    public void start(Stage stage) {
        //Step 1. Formatting the window to look as expected.
         
        //...

        //Step 2. Formatting the window to look as expected
        stage.setTitle("Duke");
        stage.setResizable(false);
        stage.setMinHeight(600.0);
        stage.setMinWidth(400.0);
        
        mainLayout.setPrefSize(400.0, 600.0);
        
        scrollPane.setPrefSize(385, 535);
        scrollPane.setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
        scrollPane.setVbarPolicy(ScrollPane.ScrollBarPolicy.ALWAYS);
        
        scrollPane.setVvalue(1.0);
        scrollPane.setFitToWidth(true);
        
        // You will need to import `javafx.scene.layout.Region` for this. 
        dialogContainer.setPrefHeight(Region.USE_COMPUTED_SIZE);
        
        userInput.setPrefWidth(325.0);
        
        sendButton.setPrefWidth(55.0);
        
        AnchorPane.setTopAnchor(scrollPane, 1.0);
        
        AnchorPane.setBottomAnchor(sendButton, 1.0);
        AnchorPane.setRightAnchor(sendButton, 1.0);
        
        AnchorPane.setLeftAnchor(userInput , 1.0);
        AnchorPane.setBottomAnchor(userInput, 1.0);

        // more code to be added here later
    }

Run the application again. It should now look like this:

Exercises

  1. In the tutorial, we used an AnchorPane to achieve the desired layout.

    1. Can you find other ways to obtain a similar layout?
    2. What are the advantages and disadvantages of your layout?
  2. Try interacting with the application

    1. What happens when you press the Enter key or left-click the send button?
    2. Why?

What's next? JavaFX tutorial part 3 - Interacting with the user | JavaFX Tutorial ToC


Authors:

  • Initial Version: Jeffry Lum