如何在Java中创建gnome gtk通知？

Question

I'm learning javafx and want my application to be able to show gnome shell notifications. I'm using the standard gnome libraries for java. Here is a simple app that I created using javafx in which when a button is clicked, a notification will be created.

Main class

package gtknotifications;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
import org.gnome.gtk.Gtk;

/**
 *
 * @author jyotiproy
 */
public class GtkNotifications extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        Scene scene = new Scene(root);

        stage.setScene(scene);
        stage.show();
    }


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

}

FXML file

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="200" prefWidth="320" xmlns:fx="http://javafx.com/fxml/1" fx:controller="gtknotifications.FXMLDocumentController">
    <children>
        <Button layoutX="126" layoutY="90" text="Click Me!" onAction="#handleButtonAction" fx:id="button" />
        <Label layoutX="126" layoutY="120" minHeight="16" minWidth="69" fx:id="label" />
    </children>
</AnchorPane>

Fxml Controller

package gtknotifications;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import org.gnome.notify.*;
import org.gnome.gtk.*;

/**
 *
 * @author jyotiproy
 */
public class FXMLDocumentController implements Initializable {

    @FXML
    private Label label;

    @FXML
    private void handleButtonAction(ActionEvent event) {
        Notification notify = new Notification("Test", "This is a Test Gtk Notification","");
        notify.setTimeout(1000);
        notify.show();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    

}

The error I'm getting while clicking the button is

Caused by: org.freedesktop.bindings.FatalError: 

You *must* call Gtk.init() before using anything else in java-gnome!

and

Caused by: java.lang.reflect.InvocationTargetException

Why are these errors coming and how to get rid of them?

EDIT As the comments mentioned and the answer instructed I ran the code with adding the Gtk.init(new String[0]); in the start method of the main class but I got the following errors.

DANGER: GLib-GObject-WARNING, cannot register existing type 'GdkDisplayManager'
DANGER: GLib-CRITICAL, g_once_init_leave: assertion 'result != 0' failed
DANGER: GLib-GObject-CRITICAL, g_object_new_with_properties: assertion 'G_TYPE_IS_OBJECT (object_type)' failed

After showing these, the window doesn't load and no stack traces are shown. The build also doesn't stop and needs to be force closed.

Answer 1

As per the error message you are supposed to call the org.gnome.gtk.Gtk.init(String[]) method somewhere early in your application lifecycle, before you attempt to use any GTK features. As per the method javadoc:

Initialize the GTK libraries. This must be called before any other org.gnome.* classes are used.

You could try the below:

@Override
public void start(Stage stage) throws Exception {
    Gtk.init(new String[0]);
    Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));
    ...