How to use FileChooser in gluon when platform is Desktop?

I know that Gluon mobile can not use FileChooser. But my question is that when I try to use PicturesService to loadImageFromGallery in Desktop and it is not working. So I wonder to detect when platform is Desktop then use FileChooser. But just can't get stage? Can you help to how to solve it?

FileChooser fileChooser = new FileChooser();
File file = fileChooser.showOpenDialog(stage);
                                       ^^^^^

If you check the source code for the Pictures service in Charm Down, there is no DesktopPicturesService implemented (yet).

This means that the call to service.loadImageFromGallery():

Services.get(PicturesService.class).ifPresent(service -> service.loadImageFromGallery());

won't be done if you are running on Desktop.

A quick solution is detecting that you are running on Desktop, and call the FileChooser directly, else use the pictures service:

if (Platform.isDesktop()) {
    FileChooser...
} else {
    Services.get(PicturesService.class).ifPresent(service -> service.loadImageFromGallery());
} 

For a better integration, nothing prevents you from adding the missing DesktopPicturesService implementation to your project, and include a FileChooser, to be able to load a picture in your application.

For that you just need to:

• add the pictures plugin to the list of services in DownConfig (build.gradle)
• add to the Desktop/Java Packages folder the following package: com.gluonhq.charm.down.plugins.desktop
• add the class DesktopPicturesService to that package, that implements PicturesService, and implement the required methods:

DesktopPicturesService.java

public class DesktopPicturesService implements PicturesService {

    @Override
    public Optional<Image> takePhoto(boolean savePhoto) {
        throw new UnsupportedOperationException("Not supported yet."); 
    }

    @Override
    public Optional<Image> loadImageFromGallery() {
        throw new UnsupportedOperationException("Not supported yet.");
    }

}

• Now add the FileChooser:

This is a simple implementation:

@Override
public Optional<Image> loadImageFromGallery() {
    FileChooser fileChooser = new FileChooser();
    FileChooser.ExtensionFilter extFilterJPG = new FileChooser.ExtensionFilter("JPG files (*.jpg)", "*.JPG");
    fileChooser.getExtensionFilters().addAll(extFilterJPG);

    try {
        File file = fileChooser.showOpenDialog(null);
        if (file != null) {
            Image image = new Image(new FileInputStream(file));
            return Optional.ofNullable(image);
        }
    } catch (FileNotFoundException ex) {}
    return Optional.empty();
}

About the stage argument, you can set it to null, or get it from the MobileApplication instance:

Stage stage = MobileApplication.getInstance().getView().getScene().getWindow();

• Finally, use your service in your application.

Add an ImageView and call the service:

ImageView imageView = new ImageView();
Services.get(PicturesService.class).ifPresent(pictures -> {
    pictures.loadImageFromGallery().ifPresent(imageView::setImage);
});

This will work now on both desktop and mobile devices.

As an extra, you could also implement the takePhoto method, accessing the webCam of your desktop machine, if exists...