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)
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?
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What is the commonality between init and stop methods?
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With the application class, how can you get its parameters?
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Describe the init() method.
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When must you override the init() method?
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The init() method constructs a Scene or a Stage.
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Which method is the main entry point for the Application class?
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When must the start(Stage) method be called?
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Which method is called on the JavaFX application thread?
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The stop() method implementation in Application can be used to prepare for application exit and destroy resources.
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What does the start method receive as its parameter?
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What is a Stage object?
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Give a code example to open a basic window with the FX program.
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What is the JavaFX library good for?
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In the JavaFX Architecture, what is the JavaFX Public APIs and Scene Graph?
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In the JavaFX Architecture, what is the Graphics Systems?
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In the JavaFX Architecture, what is the Glass Windowing?
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In the JavaFX Architecture, what is the Media and Web?
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How does the Glass toolkit use the operating system?
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Which is the primary thread?
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Which thread handles the rendering?
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Which thread runs in the background and synchronizes the latest frames through the scene graph?
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What is the Scene Graph?
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What does the Scene Graph do?
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What is a node?
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A node has a single parent, except the root node, and zero or more children.
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What does each node have?
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What are some of the things a node could have?
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Scene Graph nodes include graphics primitives like shapes and texts, layout containers, images and media.
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What is the design pattern the Scene Graph is based on?
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What does the Scene Graph make easy for us?
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What does the Scene Graph maintain?
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What is the Stage?
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What is another way to look at a Stage?
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Stage extends Window but it can also have an owner Window.
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How is the Stage constructed and modified by the JavaFX Application Thread?
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Stages are meant to take the nodes directly.
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How is the Scene used?
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What must the application do for a scene graph?
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Put the following terms in order, based on which is contained in where: Pane, Control, Stage, Nodes, Scene.
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What are some examples of Shape class?
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What are some examples of Control?
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How is the ImageView used?
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How is the Pane used?
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What can nodes be?
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Branch nodes are a type of Parent.
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What are some examples of branch nodes?
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What classes are leaf nodes?
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What are some examples of leaf nodes?
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Nodes can occur numerously in the scene graph.
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What are the graphic coordinates?
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How is a shape drawn using graphic coordinates?
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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); }}
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What can you do when you need multiple screens that need to be visible?
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Scenes are tree structures and need a Root Node (branch) as the start of the hierarchy of display.
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Scenes can directly contain ImageView or Shapes.
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Scenes can directly contain UI controls.
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Shapes or any graphical objects should be kept separate from UI controls.
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UI objects are meant to be placed in _____
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What is the purpose of Pane classes?
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A Scene will be comprised of ______.
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Place nodes in ___.
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Panes in ____.
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Scenes on ____.
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What is the root node for simple shapes?
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Groups can be directly resized.
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You can apply a transform, effect, or state to all children of a Group.
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Explain the following: public Group(); public Group(Node... Children); public Group(Collection children);
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How do parent nodes handle changes of children nodes?
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How can you get access to a Group's children?
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Can you add new children to the scene graph with a Group with a list of children nodes?
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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); }}
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Describe the Shape class.
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What does the setStrokeType(StrokeType value) do?
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What does the strokeLineCapProperty do?
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Which library do you use for color and which class does it extend from?
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What is the range of RGB values the javafx.scene.paint.Color takes?
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What are other methods you can base your color values on?
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What is the Text class?
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How can you separate paragraphs with the Text class?
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Explain the following code snippet: Text t = new Text(10, 50, "This is a test");
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What happens when you don't provide x and y placement set with a Text class?
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What can you use to render text nodes differently?
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What does the Font class default to?
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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));
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What are some of the different types you can use with the FontWeight static method?
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What are some of the different types you can use with the FontPosture static method?
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What does the Line class do?
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How many arguments must you provide to a Line class and what do they do?
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What methods can you use to center a circle?
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What method can you use to change the radius of a circle?
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How can you get rounded corners for rectangles?
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Study Notes
JavaFX Application Basics
- All JavaFX applications extend the
javafx.application.Application
class. - The application launch process includes constructing an instance, calling
init()
, thenstart(Stage)
and finishing with callingstop()
. - An application terminates when
Platform.exit()
is called or the last window closes withimplicitExit
set to true. - The
start()
method must be overridden as it is abstract, and it receives aStage
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, whileText
class is a subtype displaying text. - The
Line
class specifies line segments, and setting rounded corners on rectangles usesarcWidth
andarcHeight
.
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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Test your knowledge of JavaFX with this set of flashcards. The quiz covers essential concepts, classes, and lifecycle methods in JavaFX applications. Ideal for beginners looking to reinforce their understanding of JavaFX.