javafx.application

Class Application

java.lang.Object

javafx.application.Application

Direct Known Subclasses:

Preloader

public abstract class Application
extends java.lang.Object

Application class from which JavaFX applications extend.

Life-cycle

The entry point for JavaFX applications is the Application class. The JavaFX runtime does the following, in order, whenever an application is launched:

1. Constructs an instance of the specified Application class
2. Calls the init() method
3. Calls the start(javafx.stage.Stage) method
4. Waits for the application to finish, which happens when either of the following occur:
   • the application calls Platform.exit()
   • the last window has been closed and the implicitExit attribute on Platform is true
5. Calls the stop() method

Note that the start method is abstract and must be overridden. The init and stop methods have concrete implementations that do nothing.

Parameters

Application parameters are available by calling the getParameters() method from the init() method, or any time after the init method has been called.

Threading

JavaFX creates an application thread for running the application start method, processing input events, and running animation timelines. Creation of JavaFX Scene and Stage objects as well as modification of scene graph operations to live objects (those objects already attached to a scene) must be done on the JavaFX application thread.

The Application constructor and init method are called on the launcher thread, not on the JavaFX Application Thread. This means that an application must not construct a Scene or a Stage in either the constructor or in the init method. An application may construct other JavaFX objects in the init method.

Example

The following example will illustrate a simple JavaFX application.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class MyApp extends Application {
    public void start(Stage stage) {
        Circle circ = new Circle(40, 40, 30);
        Group root = new Group(circ);
        Scene scene = new Scene(root, 400, 300);

        stage.setTitle("My JavaFX Application");
        stage.setScene(scene);
        stage.show();
    }
}
 

The above example will produce the following:

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Application.Parameters Encapsulates the set of parameters for an application.

Constructor Summary

Constructors

Constructor and Description
Application()

Method Summary

Methods

Modifier and Type	Method and Description
HostServices	getHostServices() Gets the HostServices provider for this application.
Application.Parameters	getParameters() Retrieves the parameters for this Application, including any arguments passed on the command line and any parameters specified in a JNLP file for an applet or WebStart application.
void	init() The application initialization method.
static void	launch(java.lang.Class<? extends Application> appClass, java.lang.String... args) Launch a standalone application.
static void	launch(java.lang.String... args) Launch a standalone application.
void	notifyPreloader(Preloader.PreloaderNotification info) Notifies the preloader with an application-generated notification.
abstract void	start(Stage primaryStage) The main entry point for all JavaFX applications.
void	stop() This method is called when the application should stop, and provides a convenient place to prepare for application exit and destroy resources.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Application

public Application()

Method Detail

launch

public static void launch(java.lang.Class<? extends Application> appClass,
          java.lang.String... args)

Launch a standalone application. This method is typically called from the main method(). It must not be called more than once or an exception will be thrown.

The launch method does not return until the application has exited, either via a call to Platform.exit or all of the application windows have been closed.

Typical usage is:

 public static void main(String[] args) {
     Application.launch(MyApp.class, args);
 }
 

where MyApp is a subclass of Application.

Parameters:

appClass - the application class that is constructed and executed by the launcher.

args - the command line arguments passed to the application. An application may get these parameters using the getParameters() method.

Throws:

java.lang.IllegalStateException - if this method is called more than once.

java.lang.IllegalArgumentException - if appClass is not a subclass of Application.

launch

public static void launch(java.lang.String... args)

Launch a standalone application. This method is typically called from the main method(). It must not be called more than once or an exception will be thrown. This is equivalent to launch(TheClass.class, args) where TheClass is the immediately enclosing class of the method that called launch. It must be a subclass of Application or a RuntimeException will be thrown.

The launch method does not return until the application has exited, either via a call to Platform.exit or all of the application windows have been closed.

Typical usage is:

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

Parameters:

args - the command line arguments passed to the application. An application may get these parameters using the getParameters() method.

Throws:

java.lang.IllegalStateException - if this method is called more than once.

init

public void init()
          throws java.lang.Exception

The application initialization method. This method is called immediately after the Application class is loaded and constructed. An application may override this method to perform initialization prior to the actual starting of the application.

The implementation of this method provided by the Application class does nothing.

NOTE: This method is not called on the JavaFX Application Thread. An application must not construct a Scene or a Stage in this method. An application may construct other JavaFX objects in this method.

Throws:

java.lang.Exception

start

public abstract void start(Stage primaryStage)
                    throws java.lang.Exception

The main entry point for all JavaFX applications. The start method is called after the init method has returned, and after the system is ready for the application to begin running.

NOTE: This method is called on the JavaFX Application Thread.

Parameters:

primaryStage - the primary stage for this application, onto which the application scene can be set. The primary stage will be embedded in the browser if the application was launched as an applet. Applications may create other stages, if needed, but they will not be primary stages and will not be embedded in the browser.

Throws:

java.lang.Exception

stop

public void stop()
          throws java.lang.Exception

This method is called when the application should stop, and provides a convenient place to prepare for application exit and destroy resources.

The implementation of this method provided by the Application class does nothing.

NOTE: This method is called on the JavaFX Application Thread.

Throws:

java.lang.Exception

getHostServices

public final HostServices getHostServices()

Gets the HostServices provider for this application. This provides the ability to get the code base and document base for this application, and to access the enclosing web page.

Returns:

the HostServices provider

getParameters

public final Application.Parameters getParameters()

Retrieves the parameters for this Application, including any arguments passed on the command line and any parameters specified in a JNLP file for an applet or WebStart application.

NOTE: this method should not be called from the Application constructor, as it will return null. It may be called in the init() method or any time after that.

Returns:

the parameters for this Application, or null if called from the constructor.

notifyPreloader

public final void notifyPreloader(Preloader.PreloaderNotification info)

Notifies the preloader with an application-generated notification. Application code calls this method with a PreloaderNotification that is delivered to the preloader's handleApplicationNotification() method. This is primarily useful for cases where an application wants the preloader to show progress during a long application initialization step.

Parameters:

info - the application-generated preloader notification