没有Stage的JavaFx FileChooser

Question

I am in the process of learnig JavaFx, and I encountered a problem. I was trying to use FileChooser from JavaFx the way I was used to working with JFileChooser from Swing-in the main() method. However I found out that I need a Window object. I've tried searching for a workaround, but I found none. I've also tried null (as you do in JFileChooser) and new Stage(), so those are off the table. I was trying to mimic the JFileChooser.showOpenDialog(). Is there any reasonable way to make it work?

Answer 1

The main method is not executed on the FX Application Thread, so you can't show a FileChooser from it. (You can't really do that in Swing either, unless you are using SwingUtilities.invokeLater(...) .)

In JavaFX, the responsibility for starting the application is in the start() method, which is executed on the FX Application Thread. (In many runtime environments, you don't even need a main method in JavaFX applications.)

Just show the file chooser from the start method, where you have access to the primaryStage (or can just pass null , if you like):

public class MyApp extends Application {

    public void start(Stage primaryStage) {
        FileChooser configFileChooser = new FileChooser();
        File configFile = configFileChooser.showOpenDialog(primaryStage);

        // ... parse file and create UI, etc...

        primaryStage.show();
    }

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