Programming with JavaFX

Programming with JavaFX
Tecniche di Programmazione – A.A. 2014/2015

Summary
A.A. 2014/2015Tecniche di programmazione2
1. About and History
2. Basic concepts
3. Minimal JavaFX Application
4. Application structure
5. The Scene Graph
6. Events
7. Model-View-Controller
8. The Controller in FXML
9. Properties and bindings
10. Resources

About and History
Introduction to JavaFX

GUI in Java
 Graphic framework available in Java
 Swing
 Extremely powerful, many extensions available
 Complex to master, requires low-level handling
 Hard to create visually pleasing applications
 Alternatives available
 Most notable: SWT (Eclipse)
 Still cumbersome to master
 On a different Universe, web-based user interfaces
became nicer and faster to create

JavaFX 1.0 – forget it
 JavaFX 1 and JavaFX 2 are completely different
 Version 1 relied on a “scripting language” to describe
scenes, with ‘hooks’ to activate Java code
 JavaFX 1.x is now deprecated

JavaFX 2.x
 Redesigned from scratch
 The JavaFX 2.x framework is entirely written in Java
 For visual layout, an XML file may also be used (called
FXML)
 Graphic appearance borrows from web-standard CSS
style sheets
 UI programming is based on easy to handle events and
bindings
 Oracle plans to deprecate Swing in favor of JavaFX 2
 Now called JavaFX 8 (after Java 8 – JDK 1.8)

Getting and running JavaFX
 JavaFX is already included in Oracle JDK 7 and JDK8
 Not in JDK 6.x
 Not in OpenJDK (beware, Linux users!)
 JDK 8 includes significant JavaFX improvements.
 Recommended:
 JavaFX Scene Builder
 Eclipse: e(fx)clipse plugin, available in the Eclipse Marketplace
 Download links are in the course webpage

Basic concepts

Key concepts in JavaFX
 Stage: where the application will be displayed (e.g., a
Windows’ window)
 Scene: one container of Nodes that compose one “page”
of your application
 Node: an element in the Scene, with a visual appearance
and an interactive behavior. Nodes may be hierarchically
nested
My best friend is the JavaFX JavaDoc API
http://docs.oracle.com/javase/8/javafx/api/

Some ‘Leaf’ Nodes (Controls)

Some ‘Parent’ Nodes (Container ‘Panes’)
 BorderPane (5-areas)
 Hbox,Vbox (linear sequence)
 StackPane (overlay all children)
 GridPane (row x columns)
 FlowPane (flowing boxes, wrap around)
 TilePane (flowpane with equally sized boxes)
 AnchorPane (magnetically attach nodes at corners or
sides)

Some Nodes (Charts)

Nodes family
javafx.scene.Node
Parent
Control
ChoiceBox
ComboBoxBase
ColorPicker
ComboBox
Labeled
ButtonBase
Button
CheckBox
MenuButton
ToggleButton
Cell
Label
TitledPane
ListView
MenuBar
Separator
Slider
TabPane
TextInputControl
TextArea
TextField
ToolBar
TreeView
Group
Region
Axis
Chart
Pane
AnchorPane
BorderPane
FlowPane
GridPane
HBox
StackPane
TilePane
VBox
WebView
Shape
Arc
Circle
Line
Polygon
Polyline
Rectangle
Text
Canvas
Imageview
Focus on
Panes
and
Controls

And more coming…
http://jfxtras.org/

And more coming…
http://fxexperience.com/controlsfx/

Empty JavaFX window
public class Main extends Application {
@Override
public void start(Stage stage) {
Group root = new Group(); // the root is Group or Pane
Scene scene = new Scene(root, 500, 500, Color.BLACK);
stage.setTitle("JavaFX Demo");
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}

Adding some shape
public class Main extends Application {
@Override
public void start(Stage stage) {
Group root = new Group();
Scene scene = new Scene(root, 500, 500, Color.BLACK);
stage.setTitle("JavaFX Demo");
Rectangle rect = new Rectangle(25,25,250,250);
r.setFill(Color.BLUE);
root.getChildren().add(rect);
stage.setScene(scene);
stage.show();
}
}

How to add scene content
 In Java code
 By creating and adding new Node subclasses
 Standard way, in Java (boring and error-prone)
 By using node Builder classes
 Programming pattern, later on…
 In FXML
 By writing XML directly
 By using the Scene Editor
 And loading the FXML into the application

JavaFX Scene Builder 2.0

FXML fragment
. . .
<HBox id="HBox" alignment="CENTER" spacing="15.0"
AnchorPane.rightAnchor="23.0" AnchorPane.topAnchor="22.0">
<children>
<Button id="button1" fx:id="newIssue" onAction="#newIssueFired"
text="New" />
<Button id="button2" fx:id="saveIssue" onAction="#saveIssueFired"
text="Save" />
<Button id="button3" fx:id="deleteIssue" onAction="#deleteIssueFired"
text="Delete" />
</children>
</HBox>
<ImageView id="IssueTrackingLite" layoutX="14.0" layoutY="20.0">
<image>
<Image url="@IssueTrackingLite.png" preserveRatio="true" smooth="true" />
</image>
</ImageView>
. . .

Building a scene from FXML
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(
getClass().getResource("circle.fxml"));
stage.setTitle("Circle Demo");
stage.setScene(new Scene(root, 500, 150));
stage.show();
}

Application structure

Separation of concerns

Typical Class Diagram

General rules
 A JavaFX application extends
javafx.application.Application
 The main() method should call Application.launch()
 The start() method is the main entry point for all JavaFX
applications
 Called with a Stage connected to the Operating System’s
window
 The content of the scene is represented as a hierarchical
scene graph of nodes
 Stage is the top-level JavaFX container
 Scene is the container for all content

Minimal example
public class HelloWorld extends Application {
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) {
primaryStage.setTitle("Hello World!");
StackPane root = new StackPane();
Button btn = new Button();
btn.setText("Say 'Hello World'");
root.getChildren().add(btn);
primaryStage.setScene(new Scene(root, 300, 250));
primaryStage.show();
}
}

Stage vs. Scene
javafx.stage.Stage javafx.scene.Scene
 The JavaFX Stage class is the
top level JavaFX container.
 The primary Stage is
constructed by the platform.
 Additional Stage objects may
be constructed by the
application.
 A stage can optionally have
an owner Window.
 The container for all content
in a scene graph
 The application must specify
the root Node for the scene
graph
 Root may be Group (clips),
Region, Control (resizes)
 If no initial size is specified, it
will automatically compute it

Nodes
 The Scene is populated with a tree of Nodes
 Layout components
 UI Controls
 Charts
 Shapes
 Nodes have Properties
 Visual (size, position, z-order, color, ...)
 Contents (text, value, data sets, ...)
 Programming (event handlers, controller)
 Nodes generate Events
 UI events
 Nodes can be styled with CSS

Events
 FX Event (javafx.event.Event):
 Event Source => a Node
 Event Target
 Event Type
 Usually generated after some user action
 ActionEvent,TreeModificationEvent, InputEvent, ListView.E
ditEvent, MediaErrorEvent,TableColumn.CellEditEvent,Tre
eItem.TreeModificationEvent,TreeView.EditEvent,WebEve
nt,WindowEvent,WorkerStateEvent
 You can define event handlers in your application

Properties
 Extension of the Java Beans convention
 May be used also outside JavaFX
 Encapsulate properties of an object
 Different types (string, number, object, collection, ...)
 Set/Get
 Observe changes
 Supports lazy evaluation
 Each Node has a
large set of Properties

Bindings
 Automatically connect («bind») one Property to another
Property
 Whenever the source property changes, the bound one is
automatically updated
 Multiple bindings are supported
 Lazy evaluation is supported
 Bindings may also involve computations (arithmetic operators,
if-then-else, string concatenation, ...) that are automatically
evaluated
 May be used to automate UI
 May be used to connect the Model with theView

The Scene graph

Nodes
 Root node: top level container
 Intermediate nodes:
 Containers
 Layout managers
 UI Composite controls
 Leaf (terminal) nodes:
 Shapes
 UI Controls
 Organized as a Hierarchical tree

Nodes family
javafx.scene.Node
Parent
Control
ChoiceBox
ComboBoxBase
ColorPicker
ComboBox
Labeled
ButtonBase
Button
CheckBox
MenuButton
ToggleButton
Cell
Label
TitledPane
ListView
MenuBar
Slider
TabPane
TextInputControl
TextArea
TextField
ToolBar
TreeView
Group
Region
Axis
Chart
Pane
AnchorPane
BorderPane
FlowPane
GridPane
HBox
StackPane
TilePane
VBox
WebView
Shape
Arc
Circle
Line
Polygon
Rectangle
Text
Canvas
Imageview
JavaDoc
is your
friend
Focus on
Panes
and
Controls

Exploring Controls and Examples
 JavaFX Ensemble demo
application
 Download from Oracle
site: JavaFX Demos and
Samples Downloads
 Run Ensemble.jnlp

UI Form Controls
 Controls may be
combined to construct
«Forms»
 Control Nodes have a
value property
 May be linked to application
code
 Control Nodes generate
UI Events
 Button:ActionEvent
 Text: ActionEvent,
KeyTyped, KeyPressed,
MouseClicked, ...

Layout Class Hierarchy
 Group:
 Doesn’t perform any positioning of children.
 To statically assemble a collection of nodes in fixed positions
 To apply an effect or transform to that collection.
 Region:
 base class for all general purpose layout panes
 resizable and stylable via CSS
 Supports dynamic layout by sizing and positioning children
 Control:
 the base class for all skinnable controls
 resizable and subclasses are all stylable via CSS
 Controls delegate layout to their skins (which are Regions)
 Each layout Control subclass provides API for adding content in the
appropriate place within its skin
 you do not add children to a control directly.

Creating the Scene Graph
 The Java way
 Create Control Nodes
 Set properties to new nodes
 Add new nodes to parent node
 With Constructors and/or with Builders
 The FXML way
 Create a FXML file
 Define Nodes and Properties in FXML
 Load the FXML
 (Optionally, add new nodes/properties the Java way)

Example: one text input field
TextField text = new TextField("Text");
text.setMaxSize(140, 20);
root.getChildren().add(text);
TextField text = TextFieldBuilder().create()
.maxHeight(20).maxWidth(140)
.text("Text")
.build() ;
Constructors
Builders

public class HelloDevoxx extends Application {
public static void main(String[] args)
{
launch(args);
}
@Override
public void start(Stage primaryStage)
{
primaryStage.setTitle("Hello Devoxx");
Group root = new Group();
Scene scene = new Scene(root, 400, 250,
Color.ALICEBLUE);
Text text = new Text();
text.setX(105);
text.setY(120);
text.setFont(new Font(30));
text.setText("Hello Devoxx");
primaryStage.setScene(scene);
}
}

public void start(Stage primaryStage)
{
primaryStage.setTitle("Hello Devoxx");
primaryStage.setScene(SceneBuilder.create()
.width(400).height(250).fill(Color.ALICEBLUE)
.root(GroupBuilder.create().children(
TextBuilder.create()
.x(105).y(120)
.text("Hello Devoxx")
.font(new Font(30)).build()
).build()
).build());
}

The FXML way...
 XML-based format
 Nested tree of XML Elements, corresponding to Nodes
 XML Attributes corresponding to (initial) properties of
nodes
 JavaFX Scene Builder is a GUI for creating FXML files
 The FXMLLoader class reads a FXML file and creates all
the Nodes

Example

JavaFX Scene Builder

FXMLLoader
@Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(
getClass().getResource("fxml_example.fxml"));
stage.setTitle("FXML Welcome");
stage.setScene(new Scene(root, 300, 275));
stage.show();
}

Linking FXML and Java
 FXML element may have an associated attribute fx:id
 Nodes may be later retrieved by
 public Node lookup(java.lang.String selector)
 Finds a node with a specified ID in the current sub-tree
 Example:
 scene.lookup("#myId");
 Node references can also be «injected» using the
@FXML annotation (see later)

Interacting with Nodes
 In JavaFX applications, events are notifications that
something has happened.
 An event represents an occurrence of something of interest to
the application
 As a user clicks a button, presses a key, moves a mouse, or
performs other actions, events are dispatched.
 Registered event filters and event handlers within the
application
 receive the event and
 provide a response.

What is an event?

Event propagation
 Events are generated on the source node
 Events propagated in the scene graph hierarchy («dispatch
chain»), in two phases
 Dispatching: downwards, from root to source node
 Processes Event Filters registered in the nodes
 Bubbling: upwards, from source node to root
 Processes Event Handlers registered in the nodes
 If you want an application to be notified
when an event occurs, register a filter
or a handler for the event
 Handlers may “consume” the event

Event Handlers
 Implements the EventHandler interface
 Executed during the event bubbling phase.
 If does not consume the event, it is propagated to the
parent.
 A node can register more than one handler.
 Handlers for a specific event type are executed before
handlers for generic event types.
 For example, a handler for the KeyEvent.KEY_TYPED event is
called before the handler for the InputEvent.ANY event.
 To consume an event, call the consume() method

Registering Event Handlers
 setOnEvent-type(
EventHandler<? super event-class> value )
 Event-Type
 The type of event that the handler processes (e.g. setOnKeyTyped,
setOnMouseClicked, ...)
 Event-class
 The class that defines the event type (e.g., KeyEvent , MouseEvent, ...)
 Value
 The event handler for event-class (or for one of its super classes)
 Must implement: public void handle(ActionEvent event)
 May be a regular class or an anonymous inline class

Example
class ButtonActionHandler implements
javafx.event.EventHandler<ActionEvent> {
public ButtonActionHandler (/*params*/) {
// constructor - if needed
}
@Override
public void handle(ActionEvent event) {
Button b = (Button)event.getSource() ;
//...do something
String buttonText = b.getText() ;
// ...
}
}
Button btn = new Button() ;
btn.setOnAction(new ButtonActionHandler()) ;
Event Handler
Registration

Example (inline definition)
btn.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent event) {
System.out.println("Hello World");
}
});
Registration &
Anonymous event handler

Model-View-Controller
JavaFX programming

Application complexity and MVC
 Interactive, graphical applications exhibit complex
interaction patterns
 Flow of control is in the hand of the user
 Actions are mainly asynchronous
 How to organize the program?
 Where to store data?
 How to decouple application logic from interface details?
 How to keep in sync the inner data with the visibile
interface?

Media Player example

MVC pattern defined

Normal life-cycle of interaction

Mapping concepts to JavaFX
 View: presenting the UI
 FXML
 The Nodes in the Scene Graph
 Controller: reacting to user actions
 Set of event handlers
 Model: handling the data
 Class(es) including data
 Persistent data in Data Bases

Design Exercise
 Imagine an application managing a list of items (e.g.,
names)
 Different items in the user interface should manage the
same set of data, with different criteria and actions
 Where do you declare the data class?
 Which class should have access to which?
 Who creates what objects?

A possible
solution

The Controller in FXML
JavaFX programming

The Controller in FXML
 Several attributes in FXML help in the definition of the
Controller behavior associated to a scene
 Identification of the Controller class
 Injection of Node identifiers (references)
 Registration of event handlers
 Additionally, the JavaFX Scene Builder may generate a
«controller skeleton» for inclusion in the project

Defining the Controller class
 The Root element of the scene
graph may specify a fx:
controller attribute
 <BorderPane
id="BorderPane"
xmlns:fx="http://javafx.com
/fxml"
fx:controller="it.polito.te
cnprogr.RuzzleController">

fx:controller attribute
 Associate a "controller" class with an FXML document
 Automatically create the instance when FXML is loaded
 Should include event handler methods
 May include an initialize() method
 public void initialize();
 called once when the contents of its associated document have
been completely loaded
 any necessary post-processing on the content

Accessing the controller instance
 The Application often needs to communicate with the
controller object
 E.g., to call setModel()
 FXMLLoader provides this information
URL location = getClass().getResource("example.fxml");
FXMLLoader fxmlLoader = new FXMLLoader(location);
Pane root = (Pane)fxmlLoader.load();
MyController controller =
(MyController)fxmlLoader.getController();

Injection of Node references
 The controller code may directly access various Nodes in
the associated scene graph
 The attribute @FXML associates a Node variable with
the corresponding node, with the same fx:id value as the
variable name
 No more error-prone «lookup» calls...
 Local variables in the controller instance
 Try:View | Show Sample Controller Skeleton on the
Scene Builder!
@FXML // fx:id="theTitle"
private Label theTitle;

Registration of Event Handlers
 In FXML, you may set a event handler
through attributes
 onAction, onKeyTyped, onMouseClicked,
... hundreds more ...
 The value should be the #name of a
method in the controller class
 With the right signature for the event
type
<Button fx:id="cercaBtn"
onAction="#doCercaParola"
text="Cerca" />
@FXML
void doCercaParola (
ActionEvent event ) {

Resources

Resources
 Official
 http://www.oracle.com/us/technologies/java/fx/overview/index.
html
 http://www.oracle.com/technetwork/java/javafx/overview/index
.html
 Documents
 http://docs.oracle.com/javafx/
 http://docs.oracle.com/javafx/2/api/index.html
 Blogs
 http://fxexperience.com/
 http://www.learnjavafx.typepad.com/weblog/
 http://community.java.net/community/javafx

Resources
 API
 http://docs.oracle.com/javafx/2/api/index.html
 Slides/Tips
 http://www.slideshare.net/steveonjava/java-fx-20-a-developers-guide
 http://refcardz.dzone.com/refcardz/getting-started-javafx
 Tutorials/Articles
 http://docs.oracle.com/javafx/2/events/jfxpub-events.htm
 http://amyfowlersblog.wordpress.com/2011/06/02/javafx2-0-layout-a-
class-tour/
 Examples (Downloads)
 JavaFX Demos and Samples, at
http://www.oracle.com/technetwork/java/javase/downloads/jdk7-
downloads-1880260.html

Resources
 FXML Controller
 http://docs.oracle.com/javafx/2/api/javafx/fxml/doc-
files/introduction_to_fxml.html#controllers
 Charts
 Using JavaFX Charts tutorial:
http://docs.oracle.com/javafx/2/charts/jfxpub-charts.htm
 Books
 Head First Design Patterns, chapter 12

Resources
 Properties and Bindings
 http://docs.oracle.com/javafx/2/binding/jfxpub-binding.htm
 http://thierrywasyl.wordpress.com/2012/07/29/properties-and-
bindings-in-javafx/

Licenza d’uso
 Queste diapositive sono distribuite con licenza Creative Commons
“Attribuzione - Non commerciale - Condividi allo stesso modo (CC
BY-NC-SA)”
 Sei libero:
 di riprodurre, distribuire, comunicare al pubblico, esporre in pubblico,
rappresentare, eseguire e recitare quest'opera
 di modificare quest'opera
 Alle seguenti condizioni:
 Attribuzione — Devi attribuire la paternità dell'opera agli autori
originali e in modo tale da non suggerire che essi avallino te o il modo in
cui tu usi l'opera.
 Non commerciale — Non puoi usare quest'opera per fini
commerciali.
 Condividi allo stesso modo — Se alteri o trasformi quest'opera, o se
la usi per crearne un'altra, puoi distribuire l'opera risultante solo con una
licenza identica o equivalente a questa.
 http://creativecommons.org/licenses/by-nc-sa/3.0/

Programming with JavaFX

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