Intro to JavaFX Flashcards

Questions and Answers

Which class does all JavaFX applications extend?

javafx.application.Application

What occurs in the process with JavaFX runtime when an Application is launched? (Select all that apply)

Constructs an instance of the specified Application class. (correct)

Waits for the application to finish. (correct)

Calls the start(javafx.stage.Stage) method. (correct)

Calls the init() method. (correct)

When does an application finish? What must occur for an application to be terminated?

Either the application calls Platform.exit() or the last window has been closed and the implicitExit attribute on Platform is true.

What must you do with the start method?

It must be overridden because it's an abstract method. Signup and view all the answers

What is the commonality between init and stop methods?

They have concrete implementations that do nothing. Signup and view all the answers

With the application class, how can you get its parameters?

By calling the getParameters() method. Signup and view all the answers

Describe the init() method.

The implementation in Application does nothing. It's a hook. Signup and view all the answers

When must you override the init() method?

It must be overridden prior to starting the application to perform initialization. Signup and view all the answers

The init() method constructs a Scene or a Stage.

False Signup and view all the answers

Which method is the main entry point for the Application class?

The start(Stage) method. Signup and view all the answers

When must the start(Stage) method be called?

It is called once the init() method has returned. Signup and view all the answers

Which method is called on the JavaFX application thread?

The start(Stage) method. Signup and view all the answers

The stop() method implementation in Application can be used to prepare for application exit and destroy resources.

False Signup and view all the answers

What does the start method receive as its parameter?

It receives a Stage object. Signup and view all the answers

What is a Stage object?

It is a top-level GUI container. Signup and view all the answers

Give a code example to open a basic window with the FX program.

import javafx.application.Application; import javafx.stage.Stage; public class MyWindow extends Application{ @Override public void start(Stage stage){ stage.setTitle("Basic Window Demo"); stage.show(); } public static void main(String[] args){ launch(args); } } Signup and view all the answers

What is the JavaFX library good for?

It's a set of graphics and media packages for making rich client applications. Signup and view all the answers

In the JavaFX Architecture, what is the JavaFX Public APIs and Scene Graph?

It is a complete set of public APIs for application development. Signup and view all the answers

In the JavaFX Architecture, what is the Graphics Systems?

They are implementation details which support 2D and 3D scene graph and software rendering if needed. Signup and view all the answers

In the JavaFX Architecture, what is the Glass Windowing?

It connects JavaFX to the native operating system and handles the event queue to manage threads. Signup and view all the answers

In the JavaFX Architecture, what is the Media and Web?

Visual and audio support and full web viewer with browsing. Signup and view all the answers

How does the Glass toolkit use the operating system?

For scheduling thread and thread usages. Signup and view all the answers

Which is the primary thread?

The JavaFX Application Thread. Signup and view all the answers

Which thread handles the rendering?

The Prism Render Thread. Signup and view all the answers

Which thread runs in the background and synchronizes the latest frames through the scene graph?

Media Thread. Signup and view all the answers

What is the Scene Graph?

It is a hierarchical tree of nodes that represent all visual elements of the application's user interface. Signup and view all the answers

What does the Scene Graph do?

It can handle input and can be rendered as in drawn to the screen. Signup and view all the answers

What is a node?

It is a single element in a scene graph, a base class for elements. Signup and view all the answers

A node has a single parent, except the root node, and zero or more children.

True Signup and view all the answers

What does each node have?

An ID, style class, and a bounding volume. Signup and view all the answers

What are some of the things a node could have?

Effects like blurs and shadows, opacity, transforms, event handlers, application-specific state. Signup and view all the answers

Scene Graph nodes include graphics primitives like shapes and texts, layout containers, images and media.

True Signup and view all the answers

What is the design pattern the Scene Graph is based on?

Composite Design Pattern. Signup and view all the answers

What does the Scene Graph make easy for us?

It makes graphical user interfaces easier to create, especially when complex visual effects and transformations are involved. Signup and view all the answers

What does the Scene Graph maintain?

It maintains the model of all graphical objects and knows what objects to display, what screen areas need repainting and how to render it all efficiently. Signup and view all the answers

What is the Stage?

It is the top-level JavaFX container, constructed by the platform. Signup and view all the answers

What is another way to look at a Stage?

As a window in which we place components. Signup and view all the answers

Stage extends Window but it can also have an owner Window.

True Signup and view all the answers

How is the Stage constructed and modified by the JavaFX Application Thread?

The start method in Application passes in the stage as a parameter. The show() method displays the stage. Signup and view all the answers

Stages are meant to take the nodes directly.

False Signup and view all the answers

How is the Scene used?

It is the container for all content in a scene graph. Signup and view all the answers

What must the application do for a scene graph?

It must specify a root (or Parent) node for the scene graph. Signup and view all the answers

Put the following terms in order, based on which is contained in where: Pane, Control, Stage, Nodes, Scene.

Stage contains the scene. The scene contains the Pane or Control, both under the Parent. Then the nodes are contained in the Parent. Signup and view all the answers

What are some examples of Shape class?

Line, Circle, Ellipse, Rectangle, Polyline, and Text. Signup and view all the answers

What are some examples of Control?

UI controls like label, text field, buttons, checkbox, radio button, and text area. Signup and view all the answers

How is the ImageView used?

For displaying an image. Signup and view all the answers

How is the Pane used?

Panes are used to hold nodes. Signup and view all the answers

What can nodes be?

Shapes, image views, UI controls, and panes. Signup and view all the answers

Branch nodes are a type of Parent.

True Signup and view all the answers

What are some examples of branch nodes?

Concrete subclasses like Group, Region, and Control, or subclasses like Pane or layout panes. Signup and view all the answers

What classes are leaf nodes?

Classes that are visual components or others that can't have children. Signup and view all the answers

What are some examples of leaf nodes?

Shape, ImageView, and UI control. Signup and view all the answers

Nodes can occur numerously in the scene graph.

False Signup and view all the answers

What are the graphic coordinates?

The origin is at the top left corner. Signup and view all the answers

How is a shape drawn using graphic coordinates?

It is centered at or its baseline is at the origin. Signup and view all the answers

Explain the following code snippet: import javafx.application.Application; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.shape.Circle; import javafx.stage.Stage; public class MyCircleApp extends Application{ Circle circ = new Circle(40, 40, 30); Group root = new Group(circ); Scene scene = new Scene(root, 400, 300); stage.setTitle("My JavaFX Circle App"); stage.setScene(stage); stage.show(); public static void main(String[] args){ Application.launch(args); }}

MyCircleApp extends Application sets up as a JavaFX application. Circle circ = new Circle(...) is the shape node- leaf node. Group root = new Group(...) is the parent node, or the root. Scene scene = new Scene(...) sets the scene with the root node following the width and height of the scene. Signup and view all the answers

What can you do when you need multiple screens that need to be visible?

You can set different scenes as needed with a stage. Signup and view all the answers

Scenes are tree structures and need a Root Node (branch) as the start of the hierarchy of display.

True Signup and view all the answers

Scenes can directly contain ImageView or Shapes.

False Signup and view all the answers

Scenes can directly contain UI controls.

True Signup and view all the answers

Shapes or any graphical objects should be kept separate from UI controls.

True Signup and view all the answers

UI objects are meant to be placed in _____

Pane class Signup and view all the answers

What is the purpose of Pane classes?

It is to make the layout of UI controls easier. Signup and view all the answers

A Scene will be comprised of ______.

multiple panes Signup and view all the answers

Place nodes in ___.

panes Signup and view all the answers

Panes in ____.

scenes Signup and view all the answers

Scenes on ____.

Stage. Signup and view all the answers

What is the root node for simple shapes?

Group. Signup and view all the answers

Groups can be directly resized.

False Signup and view all the answers

You can apply a transform, effect, or state to all children of a Group.

True Signup and view all the answers

Explain the following: public Group(); public Group(Node... Children); public Group(Collection children);

These are constructors for the Group. Group has 3 constructors. A default one with no children. The Group(Node... Children) constructs a group consisting of children which can receive an array or a sequence of arguments. Group(Collection children) constructs a group consisting of the given children. Signup and view all the answers

How do parent nodes handle changes of children nodes?

Parent nodes handle changes to the scene graph by listening to the changes in the ObservableList of children nodes. Signup and view all the answers

How can you get access to a Group's children?

Using the getChildren() method. Signup and view all the answers

Can you add new children to the scene graph with a Group with a list of children nodes?

True Signup and view all the answers

Describe the coding logic behind the code snippet below: public class ShapeDemo extends Application{ @Override public void start(Stage stage){ Group root = new Group(); Scene scene = new Scene(root, 500, 500, Color.CADETBLUE); stage.setTitle("JavaFx Shape Demo"); //Make nodes to add to the scene graph //Add Nodes to scene graph //root.getChildren().addAll(...); stage.setScene(scene); stage.setScene(scene); stage.show(); } public static void main(String[] args){ launch(args); }}

First, you create a Group which becomes the root of the scene graph. Then you set up the scene to point to the root with additional descriptors of what the background should be like using a color. Then you create nodes that you would eventually add to the scene graph. Then you actually add the nodes to the scene graph by using Group methods such as getChildren() to addAll(...) with nodes each separated by a comma. Signup and view all the answers

Describe the Shape class.

It extends a Node. It's an abstract class with common properties for objects that represent some form of geometric shapes. Signup and view all the answers

What does the setStrokeType(StrokeType value) do?

It defines the direction that the strokeWidth is applied to the boundary of the shape. It can either be inside, centered, or outside of the shape. Signup and view all the answers

What does the strokeLineCapProperty do?

It defines possible end cap styles: StrokeLineCap.Butt, StrokeLineCap.Round, StrokeLineCap.Square. Signup and view all the answers

Which library do you use for color and which class does it extend from?

javafx.scene.paint.Color and extends from Paint. Signup and view all the answers

What is the range of RGB values the javafx.scene.paint.Color takes?

From 0.0 to 1.0. Signup and view all the answers

What are other methods you can base your color values on?

Integer RGB values (0-255), HSB (hue, saturation, value), Hex web value. Signup and view all the answers

What is the Text class?

It's a subclass of Shape and defines a node that displays text. Signup and view all the answers

How can you separate paragraphs with the Text class?

Using \n. Signup and view all the answers

Explain the following code snippet: Text t = new Text(10, 50, "This is a test");

The 10 and 50 are x and y placement set for the text. The text is aligned to the bottom left corner. Signup and view all the answers

What happens when you don't provide x and y placement set with a Text class?

False Signup and view all the answers

What can you use to render text nodes differently?

By using the Font class. Signup and view all the answers

What does the Font class default to?

System's default font. Signup and view all the answers

Explain the following: myText.setFont(new Font(size)); myText.setFont(new Font("Verdana", size)); myText.setFont(Font.font("verdana", FontWeight.EXTRA_BOLD, FontPosture.ITALIC, 20));

The first changes the size of the myText font. The second changes the size and the style of font. The last one changes the style, the weight, and posture of the font with size using static factory methods provided by the Font class. Signup and view all the answers

What are some of the different types you can use with the FontWeight static method?

BLACK, BOLD, LIGHT, MEDIUM, NORMAL, THIN. Signup and view all the answers

What are some of the different types you can use with the FontPosture static method?

ITALIC, REGULAR. Signup and view all the answers

What does the Line class do?

It represents a line segment in (x,y) space. Signup and view all the answers

How many arguments must you provide to a Line class and what do they do?

For the default constructor, it creates an empty instance of Line. Otherwise, it takes four arguments of double type: startX, startY, endX, and endY determine where the line starts and ends. Signup and view all the answers

What methods can you use to center a circle?

setCenterX and setCenterY. Signup and view all the answers

What method can you use to change the radius of a circle?

setRadius. Signup and view all the answers

How can you get rounded corners for rectangles?

Using the arcWidth and arcHeight properties to positive values. Signup and view all the answers

Study Notes

JavaFX Application Basics

All JavaFX applications extend the javafx.application.Application class.
The application launch process includes constructing an instance, calling init(), then start(Stage) and finishing with calling stop().
An application terminates when Platform.exit() is called or the last window closes with implicitExit set to true.
The start() method must be overridden as it is abstract, and it receives a Stage object as a parameter.

Initialization and Lifecycle

init() is a hook with a concrete implementation that does nothing, used for application initialization.
init() must be overridden before the application starts to perform necessary initializations.
stop() likewise has a default implementation doing nothing, acting as a hook to prepare for application exit.

Scene and Stage

The Stage is the top-level container in a JavaFX application, akin to a window.
A Scene must have a root node (Parent) and contains elements like Panes or Controls.
The Scene Graph is a hierarchical tree representing UI elements, maintaining graphical object models and rendering instructions.
The Stage displays scenes that contain nodes, but cannot hold nodes directly.

Nodes and Graphics

A node is an element in the scene graph and can be a shape, image view, UI control, or pane, with properties like ID and style class.
Nodes can have children except for the root node, adhering to a single-parent rule.
The Shape class is abstract, representing geometric shapes, while Text class is a subtype displaying text.
The Line class specifies line segments, and setting rounded corners on rectangles uses arcWidth and arcHeight.

JavaFX Architecture Components

The JavaFX architecture includes Public APIs for application development, Graphics Systems for rendering, and a Glass Windowing layer for OS connection.
The JavaFX Public APIs provide a comprehensive toolkit for creating applications, while Graphics Systems support rendering through both 2D and 3D scenes.
Media support in JavaFX allows for visual and audio playback, including web content viewing.

Color and Font in JavaFX

The javafx.scene.paint.Color class defines colors with RGB values ranging from 0.0 to 1.0, with alternative methods including integer values and HSB.
The Font class controls text rendering defaults to the system's font, with methods to change font size, style, and posture.

Event Handling and Concurrency

The JavaFX Application Thread is the primary thread for UI updates, while rendering is handled separately by the Prism Render Thread to enhance performance on multi-processor systems.
Background media tasks synchronize scene updates through the Media Thread.

Managing Nodes

Groups act as parent nodes in a scene, allowing multiple children to be added and transformed collectively.
Modifications to the scene graph are tracked through an ObservableList of children nodes.
Nodes can exist only once in the scene graph structure, ensuring a clear hierarchy.

Practical Implementation

Code snippets demonstrate creating a basic application, setting up scenes, and manipulating graphical elements like circles and shapes.
For multiple screens, multiple scenes can be set on a single stage.

Additional Features

JavaFX supports layout management through various Pane classes that aid arrangement of UI controls.
It is recommended to keep UI controls and graphical objects separate to optimize rendering and layout structures.

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