Question

Please have a look at the following code of JavaFX and CSS.

Login2.java

package helloworld;

import javafx.application.Application;
import javafx.stage.*;
import javafx.scene.*;
import javafx.event.*;
import javafx.geometry.Pos;
import javafx.scene.control.*;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Text;

public class Login2 extends Application
{
    private Text welcome, message;
    private Label userName, password;
    private Button btn;
    private GridPane grid;
    private TextField userNameField;
    private PasswordField passwordField;
    private Scene scene;
    private HBox hbox, hbox2;



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

    @Override
    public void start(Stage stage)
    {
        //Intializing instance Varaibles
        welcome = new Text("Welcome");
        message = new Text();

        userName = new Label("User Name: ");
        password = new Label("Password: ");

        btn = new Button("Submit");
        btn.setOnAction(new Action());

        userNameField = new TextField();
        passwordField = new PasswordField();

        grid = new GridPane();
        grid.setAlignment(Pos.CENTER);
        grid.setVgap(10);
        grid.setHgap(10);


        //Creating the GUI

        hbox = new HBox();
        hbox.getChildren().add(btn);
        hbox.setAlignment(Pos.BOTTOM_RIGHT);

        hbox2 = new HBox();
        hbox2.getChildren().add(message);
        hbox2.setAlignment(Pos.BOTTOM_RIGHT);

        grid.add(welcome,0,0);
        grid.add(userName,0,1);
        grid.add(userNameField,1,1);
        grid.add(password,0,2);
        grid.add(passwordField,1,2);
        grid.add(hbox,1,3);
        grid.add(hbox2,1,4);



        scene = new Scene(grid,300,275);


        stage.setTitle("Welcome Form");
        stage.setScene(scene);

        scene.getStylesheets().add(Login2.class.getResource("Login.css").toExternalForm());
        stage.show();
    }

    private class Action implements EventHandler<ActionEvent>
    {
        public void handle(ActionEvent ae)
        {
            message.setFill(Color.CRIMSON);
            message.setText("You pressed the button");
        }
    }
}

Login.css

/* 
    Document   : Login
    Created on : Jul 14, 2012, 8:04:31 PM
    Author     : Yohan
    Description:
        Purpose of the stylesheet follows.
*/

.root {

   -fx-background-image: url(Desert.jpg);
}

When I run this, I am getting the following error.

Exception in Application start method Exception in thread “main”
java.lang.RuntimeException: Exception in Application start method at
com.sun.javafx.application.LauncherImpl.launchApplication1(Unknown
Source) at com.sun.javafx.application.LauncherImpl.access$000(Unknown
Source) at com.sun.javafx.application.LauncherImpl$1.run(Unknown
Source) at java.lang.Thread.run(Thread.java:722) Caused by:
java.lang.NullPointerException at
helloworld.Login2.start(Login2.java:80) at
com.sun.javafx.application.LauncherImpl$5.run(Unknown Source) at
com.sun.javafx.application.PlatformImpl$4.run(Unknown Source) at
com.sun.javafx.application.PlatformImpl$3.run(Unknown Source) at
com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at
com.sun.glass.ui.win.WinApplication.access$100(Unknown Source) at
com.sun.glass.ui.win.WinApplication$2$1.run(Unknown Source) … 1
more Java Result: 1

The uploaded image shows my folder structure.

Why I am getting this error? I can’t understand! This is my third JavaFX code anyway. Please help!

Answer 1

In Netbeans, with default project settings, most of time when the non java resource files are added to the package structure, the project needs to be rebuilded from the scratch. This way new resources will be copied to the “build” folder where the compiled java files are stored and run (without NullPointerException). The rebuild can be done by right clicking the project and doing “Clean and Build”.