# Javafx Application Lifecycle

> Manage the JavaFX Application lifecycle, primary stage setup, startup sequencing, and shutdown behavior.

- Skill: `johannesrabauer/javafx-application-lifecycle` (Agent Skill)
- Install (CLI): `npx skillmds@latest add johannesrabauer/javafx-application-lifecycle`
- Raw SKILL.md: https://api.skillmd.com/api/skills/johannesrabauer/javafx-application-lifecycle/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: JohannesRabauer (https://skillmd.com/u/johannesrabauer)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/johannesrabauer/javafx-application-lifecycle

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# JavaFX Application Lifecycle

Use this skill when the application already exists or the question is specifically about
`Application.init()`, `start(Stage)`, `stop()`, or primary-stage ownership rather than initial
scaffolding.

## Example

```java
package com.example.app;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.stage.Stage;

public class MainApp extends Application {

    private ExecutorService executor;

    @Override
    public void init() {
        executor = Executors.newSingleThreadExecutor();
    }

    @Override
    public void start(Stage stage) {
        stage.setTitle("Lifecycle Demo");
        stage.setScene(new Scene(new Label("Ready"), 320, 160));
        stage.show();
    }

    @Override
    public void stop() {
        executor.shutdownNow();
    }
}
```

## Setup notes

- Keep `init()` for non-UI initialization; no scene graph access belongs there.
- Treat the primary `Stage` as application-level infrastructure and pass navigation decisions through
  a shell or coordinator instead of random controllers.
- Close executors, subscriptions, file watchers, and native resources explicitly in `stop()`.

## Gotchas

- The `Stage` is only available in `start(Stage)`, not in `init()`.
- UI changes must run on the JavaFX Application Thread.
- `javafx-project-starter` is the right skill for generating a new app skeleton; this skill is for
  lifecycle semantics and ownership boundaries inside an app.