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How to synchronize ImageIcon in ImageLoader

I recently started to use multithreading in Java and I've run into a problem I assume is due to missing synchronization.
This is a ImageLoader I wrote:
package util;
import javax.swing.ImageIcon;
public class ImageLoader extends Thread {
private String file;
private ImageIcon icon;
public ImageLoader(String file) {
this.file = file;
}
#Override
public void run() {
ImageIcon icon = new ImageIcon(this.file);
this.icon = icon;
super.run();
}
public synchronized ImageIcon returnIcon() {
return this.icon;
}
}
I use this ImageLoader in my GUI-Class:
package gui;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import util.ImageLoader;
public class HauptGui extends JComponent {
public HauptGui() {
initUI();
}
private void initUI() {
int bilderAnzahl = 3;
this.setLayout(new GridLayout(1, 1));
JPanel bilderPanel = new JPanel(new GridLayout(bilderAnzahl, 1));
for (int i = 0; i < bilderAnzahl; i++) {
JLabel jbl = new JLabel();
ImageLoader loader = new ImageLoader("./Picture.jpg");
loader.start();
jbl.setIcon(loader.returnIcon());
jbl.setBorder(BorderFactory.createEtchedBorder());
jbl.setPreferredSize(new Dimension(200, 50));
bilderPanel.add(jbl);
}
JScrollPane scrPn = new JScrollPane(bilderPanel);
this.add(scrPn);
}
}
The Problem is that the returnIcon-Method of the ImageLoader gets called before the Thread calls the run-Method, therefore the ImageIcon is still null.
How do I synchronize this?

No, your problem has nothing to do with synchronization and all to do with simply requesting the image object before it has been created. The solution is to get the image object in a call-back, after it has completed its loading. A SwingWorker would work well in this situation, where you get the image object from the SwingWorker in the worker's done method by calling .get() on it, or you could use a PropertyChangeListener for your callback. See Lesson: Concurrency in Swing for the details on how to use SwingWorkers.
For example (code not tested)
public class ImageLoader2 extends SwingWorker<BufferedImage, Void> {
private String path = ""; /// String to resource path
public BufferedImage doInBackground() throws Exception {
return ImageIO.read(ImageLoader2.class.getResource(path));
}
}
and then run it like:
ImageLoader2 loader = new ImageLoader2();
loader.addPropertyChangeListener(pce -> {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
try {
BufferedImage img = loader.get();
ImageIcon icon = new ImageIcon(img);
// use icon here...
} catch catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
// handle exception here
}
}
});
loader.execute();
Side notes
you should almost never extend Thread.
Don't get the image as a File as you are doing but rather get it as a resource and use ImageIO.read(...) to do this
The resource path is relative to the class-path, not to the user's directory, and so it will likely be different from the path you use to get the image as a file.

Java Jframe ICONIFIED closing failure

Thanks to a previous question answered I am now able to start my application as a tray icon (Java frame iconified issue), however I am now running into a few different issues and I am having trouble figuring out how to fix them. When the main program runs, the console window indeed no longer launches full screen as intended, however instead of just forming a system tray icon in the bottom right corner, the window also forms a traditional minimized window on the task bar. I have noticed that previously before I made this change, when the "Hide Window" button is pressed, the main taskbar window disappears leaving only the smaller system tray icon in the right corner. It seems the changes recommended in the previous question keeps the window running, but just seems to hide it from view. How can I change this behavior? I only expected to see the small system tray icon in the bottom right corner. Also, upon exiting the main application, the tray icons don't close down. They stay open, sometimes piling up if the main application is launched multiple times. If only I could figure out where the "Hide Window" action was coming from, I feel like I could figure this out, but alas, I cant see to find the actions of that button referenced anywhere in the code. Please help!
package com.skcraft.launcher.dialog;
import com.skcraft.launcher.Launcher;
import com.skcraft.launcher.swing.LinedBoxPanel;
import com.skcraft.launcher.swing.MessageLog;
import com.skcraft.launcher.swing.SwingHelper;
import com.skcraft.launcher.util.PastebinPoster;
import com.skcraft.launcher.util.SharedLocale;
import lombok.Getter;
import lombok.NonNull;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import static com.skcraft.launcher.util.SharedLocale.tr;
/**
* A frame capable of showing messages.
*/
public class ConsoleFrame extends JFrame {
private static ConsoleFrame globalFrame;
#Getter private final Image trayRunningIcon;
#Getter private final Image trayClosedIcon;
#Getter private final MessageLog messageLog;
#Getter private LinedBoxPanel buttonsPanel;
private boolean registeredGlobalLog = false;
/**
* Construct the frame.
*
* #param numLines number of lines to show at a time
* #param colorEnabled true to enable a colored console
*/
public ConsoleFrame(int numLines, boolean colorEnabled) {
this(SharedLocale.tr("console.title"), numLines, colorEnabled);
}
/**
* Construct the frame.
*
* #param title the title of the window
* #param numLines number of lines to show at a time
* #param colorEnabled true to enable a colored console
*/
public ConsoleFrame(#NonNull String title, int numLines, boolean colorEnabled) {
messageLog = new MessageLog(numLines, colorEnabled);
trayRunningIcon = SwingHelper.createImage(Launcher.class, "tray_ok.png");
trayClosedIcon = SwingHelper.createImage(Launcher.class, "tray_closed.png");
setTitle(title);
setIconImage(trayRunningIcon);
setSize(new Dimension(650, 400));
setExtendedState(JFrame.ICONIFIED); //This is the new line of code added to minimize the window on load
initComponents();
setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent event) {
performClose();
}
});
}
/**
* Add components to the frame.
*/
private void initComponents() {
JButton pastebinButton = new JButton(SharedLocale.tr("console.uploadLog"));
JButton clearLogButton = new JButton(SharedLocale.tr("console.clearLog"));
buttonsPanel = new LinedBoxPanel(true);
buttonsPanel.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));
buttonsPanel.addElement(pastebinButton);
buttonsPanel.addElement(clearLogButton);
add(buttonsPanel, BorderLayout.NORTH);
add(messageLog, BorderLayout.CENTER);
clearLogButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
messageLog.clear();
}
});
pastebinButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
pastebinLog();
}
});
hideMessages();
}
/**
* Register the global logger if it hasn't been registered.
*/
private void registerLoggerHandler() {
if (!registeredGlobalLog) {
getMessageLog().registerLoggerHandler();
registeredGlobalLog = true;
}
}
/**
* Attempt to perform window close.
*/
protected void performClose() {
messageLog.detachGlobalHandler();
messageLog.clear();
registeredGlobalLog = false;
dispose();
}
/**
* Send the contents of the message log to a pastebin.
*/
private void pastebinLog() {
String text = messageLog.getPastableText();
// Not really bytes!
messageLog.log(tr("console.pasteUploading", text.length()), messageLog.asHighlighted());
PastebinPoster.paste(text, new PastebinPoster.PasteCallback() {
#Override
public void handleSuccess(String url) {
messageLog.log(tr("console.pasteUploaded", url), messageLog.asHighlighted());
SwingHelper.openURL(url, messageLog);
}
#Override
public void handleError(String err) {
messageLog.log(tr("console.pasteFailed", err), messageLog.asError());
}
});
}
public static void showMessages() {
ConsoleFrame frame = globalFrame;
if (frame == null) {
frame = new ConsoleFrame(10000, false);
globalFrame = frame;
frame.setTitle(SharedLocale.tr("console.launcherConsoleTitle"));
frame.registerLoggerHandler();
frame.setVisible(true);
} else {
frame.setVisible(true);
frame.registerLoggerHandler();
frame.requestFocus();
}
}
public static void hideMessages() {
ConsoleFrame frame = globalFrame;
if (frame != null) {
frame.setVisible(false);
}
}
}

How to close all children and parent windows?

I need to close all the children and parent windows when I close one window in the hierarchy.
I have three lines of windows:
My windows hierarchy - All lines start in one MainWindow. Only LoadPlayers and CreatePlayers are dialogs. All other windows are frames.
E.g. I close TablesOverview in the first line - I need to close all other windows in this line.
But windows in other lines must stay open.
Notice that TablesOverview is in two lines.
I can write the code, where I named every window that must close. But I need cleaner solution.
This code give me all opened windows - I don't know how to take only windows in one line.
Window[] windows = Window.getWindows();
This codes give me nothing.
Window[] windows = frame.getOwnedWindows();
Component comp = frame.getParent();

Java don't provides this support implicitly. So, you have to use some work around:
Solution:
Create a new class which extends JFrame
Create a data member children of type ArrayList<Your class name>. This holds the instance created by current window
Create an member method createChildWindow(). This method will create a child window and add it in to variable children
Register for event on closing the window. For this use addWindowListener() and override public void windowClosing(java.awt.event.WindowEvent windowEvent) method. In this method traverse throw the children collection and close each child(This will eventually close its subsequent children also).
Following is the complete working code
WindowTracker.java
package com.cse.test.awt;
import java.awt.FlowLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class WindowTracker extends JFrame
{
ArrayList<WindowTracker> children;
JLabel childrenCount;
public WindowTracker()
{
children = new ArrayList<>();
this.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent arg0) {
System.out.println("Closing..." + this.hashCode());
for(WindowTracker child:children)
{
child.dispatchEvent(new WindowEvent(child, WindowEvent.WINDOW_CLOSING));
}
System.out.println("Closed..." + this.hashCode());
}
});
this.setLayout(new FlowLayout(FlowLayout.RIGHT));
childrenCount = new JLabel("Children count: 0");
this.add(childrenCount);
JButton btn = new JButton("Create new child");
btn.addActionListener(e -> {WindowTracker child = getNewChild();});
this.add(btn);
this.setSize(300, 300);
this.setTitle("" + this.hashCode());
this.setVisible(true);
}
public WindowTracker getNewChild()
{
WindowTracker child = new WindowTracker();
children.add(child);
childrenCount.setText("Children count: " + children.size());
return child;
}
}
Executer.java
package com.cse.test.common;
import com.cse.test.awt.WindowTracker;
public class Executer {
public static void main(String[] args) {
// TODO Auto-generated method stub
new WindowTracker();
}
}

Dynamic splash screens for my java application

I want to create a splash screen for my Java application. I managed to do this using the NetBeans default tool that allows me to put some image in. But i want to have something "live" there, such as a progress bar showing the status of application load, some dynamic text, etc.
How do I do this? What are the things I need to know to start doing something like this?

Here is the Java tutorial walking you through exactly what you want to do. You can set the image on the command line so that it shows immediately, then you can manipulate it once the JVM is initialized to add text, progress bars, etc.
http://download.oracle.com/javase/tutorial/uiswing/misc/splashscreen.html

The trick is to create a splash screen using swing and then invoke using Java reflection the method, which is in another .java file, that loades the application. When done loading, dispose your splash screen.
After checking the code, you will understand how it works and now customize it your own way.
Here is some code:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JDialog;
/**
*
* #author martijn
*/
public class Splash {
public static void splash() {
try {
final BufferedImage img = ImageIO.read(Splash.class.getResourceAsStream("/path/to/your/splash/image/splash.png"));
JDialog dialog = new JDialog() {
#Override
public void paint(Graphics g) {
g.drawImage(img, 0, 0, null);
}
};
// use the same size as your image
dialog.setPreferredSize(new Dimension(450, 300));
dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
dialog.setUndecorated(true);
dialog.pack();
dialog.setLocationRelativeTo(null);
dialog.setVisible(true);
dialog.repaint();
try {
// Now, we are going to init the look and feel:
Class uim = Class.forName("javax.swing.UIManager");
uim.getDeclaredMethod("setLookAndFeel", String.class).invoke(null, (String) uim.getDeclaredMethod("getSystemLookAndFeelClassName").invoke(null));
// And now, we are going to invoke our loader method:
Class clazz = Class.forName("yourpackage.YourClass");
dialog.dispose();
// suppose your method is called init and is static
clazz.getDeclaredMethod("init").invoke(null);
} catch (Exception ex) {
ex.printStackTrace();
}
dialog.dispose();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}

Why is paint()/paintComponent() never called?

For the last two days I have tried to understand how Java handles graphics, but have failed miserably at just that. My main problem is understanding exactly how and when paint() (or the newer paintComponent() ) is/should be called.
In the following code I made to see when things are created, the paintComponent() is never called, unless I manually add a call to it myself or calls to JFrame.paintAll()/JFrame.paintComponents().
I renamed the paint() method to paintComponent() in hoping that would fix my problem of it never being called (even at repaint()), but no luck.
package jpanelpaint;
import java.awt.*;
import javax.imageio.*;
import javax.swing.*;
import java.io.*;
import java.util.ArrayList;
public class ImageLoadTest extends JComponent {
ArrayList<Image> list;
public ImageLoadTest() {
list = new ArrayList<Image>();
try { //create the images (a deck of 4 cards)
for(String name : createImageFileNames(4)){
System.err.println(name);
list.add(ImageIO.read(new File(name)));
}
} catch (IOException e) { }
}
protected void paintComponent(Graphics g) {
int yOffset=0;
System.err.println("ImageLoadTest.paintComponent()");
for(Image img : list) {
g.drawImage(img, 0, yOffset, null);
yOffset+=20;
}
}
public static void main(String args[]) throws InterruptedException {
JFrame frame = new JFrame("Empty JFrame");
frame.setSize(new Dimension(1000, 500));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
Thread.sleep(1000);
frame.setTitle("Loading images");
ImageLoadTest ilt = new ImageLoadTest();
frame.add(ilt);
//update the screen
//DOESN'T WORK. only works if I call frame.paintAll(frame.getGraphics())
ilt.repaint();
frame.repaint();
Thread.sleep(1000);
frame.setTitle("Setting background");
ilt.setBackground(Color.BLACK);
//update the screen - DOESN'T WORK even if I call paintAll ..
ilt.repaint();
frame.repaint();
//have to call one of these to get anything to display
// ilt.paintComponent(frame.getGraphics()); //works
frame.paintComponents(frame.getGraphics()); //works
}
//PRIVATE HELPER FUNCTIONS
private String[] createImageFileNames(int count){
String[] fileNames = new String[count];
for(int i=0; i < count; i++)
fileNames[i] = "Cards" + File.separator + (i+1) + ".bmp";
return fileNames;
}
}

One of the reasons the paintComponent() doesn't get invoked in the original code is because the component has a "zero size" and the RepaintManger is smart enough not to try and paint something with no size.
The reason the reordering of the code works is because when you add the component to the frame and then make the frame visible the layout manager is invoked to layout the component. By default a frame uses a BorderLayout and by default a component is added to the center of the BorderLayout which happens give all the space available to the component so it gets painted.
However, you change the layout manager of the content pane to be a FlowLayout, you would still have a problem because a FlowLayout respects the preferred size of the component which is zero.
So what you really need to do is assign a preferred size to you your component so layout managers can do their job.

One major issue here is you are not updating your swing components on the Event Dispatch Thread (EDT). Try wrapping all the code in your main method in the following:
SwingUtilities.invokeLater(new Runnable() {
public void run() {
// swing code here...
}
});
Also: add your ImageLoadTest to the frame before setting the frame visible. This is based on a quick cursory read of the code -- I will read it further and see what else I can find.
EDIT:
Follow my original advice above, and simplify your main method to look like the following and your paintComponent() will be called:
public static void main(String args[]) throws InterruptedException {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("Empty JFrame");
frame.setSize(new Dimension(1000, 500));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
PaintComponentTest ilt = new PaintComponentTest();
frame.add(ilt);
frame.setVisible(true);
ilt.setBackground(Color.BLACK);
}
});
}
Also I would read up on using timers to perform animation, as well as general Swing event dispatching and how/when to override various paint methods.
http://java.sun.com/products/jfc/tsc/articles/painting/
http://java.sun.com/docs/books/tutorial/uiswing/misc/timer.html
http://java.sun.com/docs/books/tutorial/uiswing/concurrency/dispatch.html

To make Tom Hawtin - tackline happy. I rewrote once again
There are several things I changed (check the lines with the //new comment)
Rewrote it completely
Split into a clean new component file (ImageLoadTest.java) and a file to test it (Tester.java)
Improvements on original posters code
call constructor of parent in ImageLoadTest constructor (super())
provided second constructor to set list of images which component should display
IMPORTANT: call to setPreferredSize() of component in constructor. If size isn't set swing of course won't paint your component. preferred size is based on max. width of all images and on sum of all image heights
call to super.paintComponent(g) in overriden paintComponent()
changed paintComponent to automatically base yOffset on height of images being drawn
GUI initialization done on EDT
as original code based on using sleep() to illustrate loading and loading of images could take a long time SwingWorker's are used
worker waits then sets new title and then loads images
on completion the worker in done() finally adds the component to the JFrame and displays it. Added component to content pane of JFrame as described in JFrame api. And as described in javadoc made necessary call to validate() on JFrame after calling add(), as the JFrame is an already visible container whichs children changed.
javdoc citation from validate()
The validate method is used to cause a
container to lay out its subcomponents
again. It should be invoked when this
container's subcomponents are modified
(added to or removed from the
container, or layout-related
information changed) after the
container has been displayed.
second worker just does some more waiting then sets background color to black
used JPanel as baseclass for ImageLoadTest to fix setBackground() which I couldn't get to work with JComponent.
So your main problems where that you didn't set the preferred size of the component and that you did not call validate() on the JFrame after adding something to the already visible container.
This should work
jpanelpaint/ImageLoadTest.java
package jpanelpaint;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JPanel;
import java.util.List;
public class ImageLoadTest extends JPanel {
private List<Image> list;
public ImageLoadTest() {
super();
}
public ImageLoadTest(List<Image> list) {
this();
this.list = list;
int height = 0;
int width = 0;
for (Image img : list) {
height += img.getHeight(this);
width = img.getWidth(this) > width ? img.getWidth(this) : width;
setPreferredSize(new Dimension(width, height));
}
}
#Override
protected void paintComponent(Graphics g) {
int yOffset=0;
super.paintComponent(g);
System.err.println("ImageLoadTest.paintComponent()");
for(Image img : list) {
g.drawImage(img, 0, yOffset, null);
yOffset+=img.getHeight(this);
}
}
}
Tester.java
import java.awt.Dimension;
import java.awt.Color;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.SwingWorker;
import javax.swing.SwingUtilities;
import java.util.List;
import java.util.ArrayList;
import java.util.concurrent.ExecutionException;
import jpanelpaint.ImageLoadTest;
public class Tester {
private JFrame frame;
private ImageLoadTest ilt;
private final int NUMBEROFFILES = 4;
private List<Image> list;
//will load the images
SwingWorker worker = new SwingWorker<List<Image>, Void>() {
#Override
public List<Image> doInBackground() throws InterruptedException {
//sleep at start so user is able to see empty jframe
Thread.sleep(1000);
//let Event-Dispatch-Thread (EDT) handle this
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setTitle("Loading images");
}
});
//sleep again so user is able to see loading has started
Thread.sleep(1000);
//loads the images and returns list<image>
return loadImages();
}
#Override
public void done() {
//this is run on the EDT anyway
try {
//get result from doInBackground
list = get();
frame.setTitle("Done loading images");
ilt = new ImageLoadTest(list);
frame.getContentPane().add(ilt);
frame.getContentPane().validate();
//start second worker of background stuff
worker2.execute();
} catch (InterruptedException ignore) {}
catch (ExecutionException e) {
String why = null;
Throwable cause = e.getCause();
if (cause != null) {
why = cause.getMessage();
} else {
why = e.getMessage();
}
System.err.println("Error retrieving file: " + why);
}
}
};
//just delay a little then set background
SwingWorker worker2 = new SwingWorker<Object, Void>() {
#Override
public List<Image> doInBackground() throws InterruptedException {
Thread.sleep(1000);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setTitle("Setting background");
}
});
Thread.sleep(1000);
return null;
}
#Override
public void done() {
ilt.setBackground(Color.BLACK);
frame.setTitle("Done!");
}
};
public static void main(String args[]) {
new Tester();
}
public Tester() {
//setupGUI
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame = new JFrame("Empty JFrame");
frame.setSize(new Dimension(1000, 500));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
//start the swingworker which loads the images
worker.execute();
}
//create image names
private String[] createImageFileNames(int count){
String[] fileNames = new String[count];
for(int i=0; i < count; i++)
fileNames[i] = "Cards" + File.separator + (i+1) + ".bmp";
return fileNames;
}
//load images
private List<Image> loadImages() {
List<Image> tmpA = new ArrayList<Image>();
try {
for(String name : createImageFileNames(NUMBEROFFILES)){
System.err.println(name);
tmpA.add(ImageIO.read(new File(name)));
}
} catch (IOException e) { }
return tmpA;
}
}

These were the main problems with the original code that caused it not to work:
not calling validate() after an add() operation
not setting the preferred size of the component.
not calling super.paintComponent() when overriding it (this made the
setBackground() call not work)
I needed to inherit from JPanel in order for it to get painted. Neither Component nor JComponent was sufficient for the setBackground() call to work, even when fixing point 3.
Having done the above, it really didn't matter if calling the method paintComponent or paint, both seemed to work as long as I remembered to call the super constructor at the start.
This info was assembled from what #jitter, #tackline, and #camickr wrote, so big kudos!
P.S. No idea if answering your own question is considered bad form, but since the information I needed was assembled from several answers, I thought the best way was upmodding the other answers and writing a sum up like this.

I recommend reading the first couple of chapters of "Filthy Rich Clients". I had been using Swing for years, but only after reading this book did I finally fully understand exactly how Java's painting mechanism works.