Show custom loading dialog with gif

Question

I am trying to get my application to display a simple loading dialog so users know when a time intensive process is working and when its done. I just want it to show a simple "loading" using a gif I downloaded. I already tried using only text and it still doesn't work.

I can get the dialog to display (and disappear) when I want it to, the problem is nothing will display on the dialog (or frame) after displaying it. I have tried many different techniques and all give the same result, a blank dialog.

I finally made a separate class to display the dialog (with loading gif) and I got it to display properly (by itself), but when I run it from my main application, it shows a black dialog again. I tested putting the gif into a JOptionPane and it works, the problem with that is I can't close it at will.

Here is my custom code.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import java.util.logging.*;
import org.w3c.dom.*;
import java.io.File;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import javax.swing.filechooser.FileNameExtensionFilter;

public class Loader implements Runnable  {

    final JFileChooser jfc = new JFileChooser();
    static JFrame frame = new JFrame();
    Frame parentUI = new  Frame();
    JDialog dialog = new JDialog();
    JLabel lbl_filename = new JLabel();
    JLabel lbl_path = new JLabel();

    static Loader load = new Loader(null);


    public static void main(String[] args) throws InterruptedException, InvocationTargetException {
        load.run();
        frame.setVisible(true);
    } 

    public Loader(Frame parent) {
        init();
        parentUI = parent;
    }

    @Override
    public void run() {
        createDialog(parentUI);
    }  

    public final void init() {
        JButton btn = new JButton("Open");

        frame.setTitle("Loader Test");
        frame.setSize(500, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setLayout(new FlowLayout());

        btn.addActionListener(new Action1());

        frame.add(btn);
        frame.add(lbl_filename);
        frame.add(lbl_path);
    }

    class Action1 implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {

            openFile();
            load.Close();
        }
    }

    private void createDialog(final Frame parent) {

        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setTitle("Loader");

        URL url = this.getClass().getResource("/resource/loader.gif");
        Icon icon = new ImageIcon(url);
        JLabel label = new JLabel(icon);
        dialog.add(label);

        dialog.pack();
        dialog.setLocationRelativeTo(parent);
    }


    public void Show(Boolean visible) {
        this.run();
        dialog.setVisible(visible);
    }

    public void Close() {
        dialog.setVisible(false);
    }

    private void setJFCFilter(String file, String ext) {
        FileNameExtensionFilter filter = new FileNameExtensionFilter(file, ext);
        jfc.setFileFilter(filter);
    }

    private void openFile() {
        File default_dir = new File(".");
        jfc.setCurrentDirectory(default_dir);
        setJFCFilter("Scalable Vector Graphics", "svg");

        int returnVal = jfc.showOpenDialog(parentUI);

        if (returnVal == JFileChooser.APPROVE_OPTION) {
            String path = jfc.getSelectedFile().getAbsolutePath();
            String fileName = jfc.getSelectedFile().getName();

            lbl_filename.setText(fileName);
            lbl_path.setText(path);

            load.Show(true);
            createDoc(path);
            load.Close();

        }
    }

    private void createDoc(String file) {
        try {
            NodeList svgIDPaths;

            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document doc = builder.parse(file);

            String xpathIDExp = "//g/@id";

            XPathFactory xpf = XPathFactory.newInstance();
            XPath xpath = xpf.newXPath();
            XPathExpression expression = xpath.compile(xpathIDExp);

            svgIDPaths = (NodeList)expression.evaluate(doc, XPathConstants.NODESET);

        } catch (Exception ex) {
            Logger.getLogger(Loader.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}  

Edit: Use this file for testing -> svg_test.svg

I have tried calling it like this:

loader.show(true);

And also in its own thread like this:

private void load(final Boolean visible) {
    Thread t = new Thread(new Runnable() {
        @Override
        public void run() {
            loader.show(visible);
        }
    });

    t.start();
}

Neither method works and gives me the same result, a blank dialog. I have had this issue in the past, but just gave up and removed it (loading dialog). I have tried it with a progress bar and simple text, nothing seems to work.

Also I tried it in a JOptionPane and it worked, but that's not desirable (I want to close/open when I want not via a button click).

 private void load() {
        ImageIcon icon = new ImageIcon(MainForm.class.getResource("/resource/loader.gif").getFile());
        JOptionPane.showMessageDialog(null, "Loading...", "Loader", JOptionPane.INFORMATION_MESSAGE, icon);
    }

I am aware you can't run multiple dialogs on the EDT and have to use a separate thread, but I'm using a separate thread and its not working (it works by itself).

(Also note I have one main application (frame) that is running/opening this second dialog).

Any assistance is appreciated.

Answer 1

You look to have a Swing threading issue where you have long-running code on the event thread messing up drawing of images, and my guess is that the long running code is in your createDoc method. Consider calling that from a background thread, such as from a SwingWorker, and calling close on your load object only after the worker has completed its work. For example something like so:

class Action1 implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {

        openFile();
        // load.Close();  // get rid of this
    }
}

// .......

private void openFile() {

    // ....

    load.Show(true);  // load dialog on event thread

    new SwingWorker<Void, Void>() {
        protected Void doInBackground() throws Exception {
            createDoc(path);  // call this from background thread
            return null;
        };

        protected void done() {
            load.Close();  // only call this once createDoc has completed
            // probably should call get() in here to catch all exceptions
        };
    }.execute();
}