JavaFX Fundamentals (Part 1) - Concepts-First Tutorial

JavaFX is easiest to learn when the focus is not “memorize classes”, but “understand the model.”
Once the model is clear, the code feels repetitive in a good way: create nodes, arrange them with a layout pane, then connect events to logic.

1) The JavaFX mental model

In JavaFX, you build a UI by creating a tree of elements (a scene graph), then showing it in a window.

Think in three layers:

• Stage: the top-level window provided by the operating system.
• Scene: the content container placed inside the Stage.
• Nodes: the actual UI building blocks (controls, shapes, layout panes, etc.) placed into the Scene.

The scene graph is a hierarchy:

• Every visible element is a Node, and branch nodes are typically Parent types that can contain children.
• The Scene holds the scene graph, and when you create a Scene you provide a root node (the top of the tree).

Illustration snippet (Stage → Scene → root node):

VBox root = new VBox();
Scene scene = new Scene(root, 400, 350);

stage.setScene(scene);
stage.show();

Practical mindset: JavaFX is not "draw pixels here"; it is "describe structure, then let JavaFX lay it out and render it."

2) Application lifecycle (what runs, and when)

JavaFX apps start by extending Application. When you launch the app, the JavaFX runtime calls lifecycle methods in order: init(), then start(Stage), and later stop().

What this means:

• start(Stage) is where you build and show the UI.
• launch(args) boots the JavaFX runtime and triggers that lifecycle.

Illustration snippet (entry point):

public static void main(String[] args) {
    launch(args);
}

A simple rule: if it belongs to the UI, it usually starts inside start(...); if it belongs to cleanup, it usually goes to stop().

3) Controls: "interactive nodes" and their properties

Controls (like text fields and buttons) are nodes that users can interact with. Most JavaFX coding is configuring controls through properties: text, prompt text, width, alignment, disabled state, etc.

For example, in a login form, the "core" controls are: - Label for readable text ("Username", "Password", feedback).
- TextField for input.
- PasswordField for secret input.
- Button for submitting.

Illustration snippet (create controls, set prompts):

TextField usernameField = new TextField();
usernameField.setPromptText("Enter your username");

PasswordField passwordField = new PasswordField();
passwordField.setPromptText("Enter your password");

Button loginBtn = new Button("Login");
Label feedbackLabel = new Label();

Good UI habit: small details (prompt text, spacing, readable labels) often matter more to users than advanced features.

4) Events: how the UI "comes alive"

JavaFX is event-driven: user actions trigger events, and event handlers react. A login form is a perfect example because it uses a small number of clear events.

Common beginner events: - Button click → attempt login (an action event). - Press Enter in the password field → attempt login (a key event).

Illustration snippet (two events, one shared action):

loginBtn.setOnAction(e -> handleLogin());

passwordField.setOnKeyPressed(e -> {
    if (e.getCode() == KeyCode.ENTER) {
        handleLogin();
    }
});

Best practice: multiple UI events should call the same "business action" method, so logic is not duplicated.

5) Layout panes: clean structure instead of manual positioning

Layout panes are containers (nodes) designed to arrange child nodes automatically.
They exist so you do not hard-code x/y coordinates, and so the UI behaves better when resized.

Start simple: VBox / HBox

VBox arranges children in a vertical column, and HBox arranges children in a horizontal row.
They are ideal for quick, readable UIs and for teaching structure before complexity.

Illustration snippet (VBox with spacing and padding):

VBox root = new VBox(10);
root.setStyle("-fx-padding: 20;");

GridPane: forms that "line up"

GridPane places nodes in a grid of rows and columns.
It’s a strong choice when you want labels aligned with their fields.

Illustration snippet (label column + field column):

grid.add(new Label("Username:"), 0, 0);
grid.add(usernameField, 1, 0);

BorderPane: the “professional app shell”

BorderPane lays out content into top, bottom, left, right, and center regions.
It's common when an app grows beyond a single form (top bar, navigation, main content, status line).

Illustration snippet (place form in the center):

BorderPane shell = new BorderPane();
shell.setCenter(formRoot);

FlowPane and StackPane: when you need special behavior

FlowPane lays out items in a flow and wraps at the boundary (useful for “chips”, tags, dynamic button sets). StackPane places nodes in a back-to-front stack (useful for overlays, badges, loading layers). [web:23]

Choosing a layout pane is not about "which is best", but about "what behavior do I want when the window changes?"

You can’t make life perfectly put together.
But you can at least fix the padding.