Class Application

public abstract class Application
extends Object

Application class from which JavaFX applications extend.

See example code MyApp.java

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.

Calling Platform.exit() is the preferred way to explicitly terminate a JavaFX Application. Directly calling System.exit(int) is an acceptable alternative, but doesn't allow the Application stop() method to run.

A JavaFX Application should not attempt to use JavaFX after the FX toolkit has terminated or from a ShutdownHook, that is, after the stop() method returns or System.exit(int) is called.

Parameters

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

See example MyApp2.java

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 Java launcher loads and initializes the specified Application class on the JavaFX Application Thread. If there is no main method in the Application class, or if the main method calls Application.launch(), then an instance of the Application is then constructed on the JavaFX Application Thread.

The init method is 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 the init method. An application may construct other JavaFX objects in the init method.

All the unhandled exceptions on the JavaFX application thread that occur during event dispatching, running animation timelines, or any other code, are forwarded to the thread's uncaught exception handler.

Maintained by John Loomis, last updated 30 January 2018