Develop Reference

JFrame don't work when adding an Image

I'm having a problem that seems a little bit strange. When I'm adding a new ImageIcon and try to run the program it just gives me a gray screen and no objects are added.
public class Ctester {
public Ctester(){
Frame();
}
public void Frame(){
JFrame fr = new JFrame();
fr.setVisible(true);
fr.setSize(500, 500);
fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
fr.setResizable(false);
JPanel p = new JPanel(new GridBagLayout());
ImageIcon icon = new ImageIcon(getClass().getResource("zippo.jpg"));
JLabel l = new JLabel(icon)
JButton bm1 = new JButton("hellu");
p.add(l);
p.add(bm1);
fr.add(p);
}
public static void main(String[]args){
new Ctester();
}
}
But if I remove the line:
ImageIcon icon = new ImageIcon(getClass.getResource("zippo.jpg"));
then it works perfect.
I'm not getting any error messages and i been looking for a while but I could only find that the problem might be something with the gridbaglayout.
How can i solve it or do I have to change layout?
(this is just a simple code based of the original as an example so any solutions that not include having to change layout is highly appreciated)

Most of the code is wrong:
Swing components should be create on the Event Dispatch Thread (EDT).
The frame should be made visible AFTER all the components have been added to the frame.
You are attempting to use a GridBagLayout, but you aren't using any GridBagConstraints when you add the components.
Method names (Frame) should NOT start with an upper case character.
Read the Swing Tutorial for Swing basics.
You can find working examples in:
How to Use GridBagLayout
How to Use Icons
so any solutions that not include having to change layout is highly appreciated
Start with the working examples and make changes for your requirements. If you start with better structured code you will have less problems.

If something draws correctly after a window resize or minimize/maximize that is a sure sign of a race condition because you are not starting your GUI on the event dispatcher thread. Your main problem is you are calling setVisible() way to early, don't call setVisible() until after you have added all components to your top-level container. The other problem is you are not starting your GUI on the event dispatcher thread. Please see the main method below in the fixed code:
public class Ctester {
public Ctester() {
Frame();
}
public void Frame() {
JFrame fr = new JFrame();
fr.setSize(500, 500);
fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
fr.setResizable(false);
JPanel p = new JPanel(new GridBagLayout());
JLabel l = new JLabel("label");
JButton bm1 = new JButton("hellu");
p.add(l);
p.add(bm1);
fr.add(p);
fr.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Ctester();
}
});
}
}

Try this code you might want to put that first line of code in a try catch just in case that it doesn't find the image.
URL iconURL = getClass().getResource("/some/package/favicon.png");
// iconURL is null when not found
ImageIcon icon = new ImageIcon(iconURL);
fr.setIconImage(icon.getImage());
Also use a .ico file if you are only using this program on Windows but use a .png if it is going to be multi-platform

JPanel doesn't update when adding Component in another class

I'm fairly new to Java Swing and I'm running into a few problems.
As a side question, when making a fairly large Java Swing Application, what is the best way to split up code?
In my case I want to have an application that has a layout just as Microsoft Word where there is a JToolBar filled with buttons and a main JPanel where changes are made based on the buttons pressed in the Tool Bar.
So as shown in the code below, I have a JFrame and I call the MainPanel class in order to create a panel and add a ToolBar with a button. When the button is pressed it adds a button to the panel. The problem comes when you click the button nothing shows up until you resize the window(in my case I simply manually drag the screen to make it larger).
public class Main {
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("MathMaker");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create the menu bar. Make it have a green background.
//MainToolBar mainTB = new MainToolBar();
MainPanel mainPanel = new MainPanel();
frame.getContentPane().add(mainPanel.getGUI(), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
public class MainPanel implements ActionListener{
JPanel mPanel;
JToolBar mToolBar;
JButton addQuestion;
public MainPanel() {
mPanel = new JPanel(new BorderLayout());
mToolBar = new JToolBar();
addQuestion = new JButton("test");
addQuestion.addActionListener(this);
mPanel.setLayout(new BorderLayout());
mPanel.setBackground(new Color(248, 213, 131));
mPanel.setPreferredSize(new Dimension(200, 180));
mToolBar.add(addQuestion);
mPanel.add(mToolBar, BorderLayout.PAGE_START);
}
public JComponent getGUI()
{
return mPanel;
}
#Override
public void actionPerformed(ActionEvent e) {
JButton temp = new JButton("temp");
mPanel.add(temp);
}
}

You should revalidate your panel
#Override
public void actionPerformed(ActionEvent e) {
JButton temp = new JButton("temp");
mPanel.add(temp);
mPanel.revalidate();
mPanel.repaint();
}

I believe you need to call revalidate() and repaint() to see the changes, here is a similar question here

The problem here is the panel is not repainted automatically.. When you resize the panel Java repaints the panel on the screen. Try repainting the panel everytime any button to modify the panel is clicked..
Just call the validate() and repaint() method with the panel

Translucent loading overlay for JFrame

I have a JFrame containing various components and I would like to add a translucent grey overlay over the top while the application is initializing various things. Ideally it would prevent interaction with the underlying components and would be able to display some "Loading..." text or a spinning wheel or something similar.
Is there a simple way to do this using Java and Swing?

Take a look at JRootPane and JLayeredPane http://docs.oracle.com/javase/tutorial/uiswing/components/rootpane.html#layeredpane
What you're asking about specifically sounds like a Glass Pane.
http://docs.oracle.com/javase/tutorial/uiswing/components/rootpane.html#glasspane
The Glass Pane prevents interaction with underlying components and can be used to display something on top of your JFrame.

As #David said, you can use the glass pane for displaying some loading text or image above the rest of the application.
As for the grey overlay: why don't you use the built in ability to disable components as long as your application is loading? Disabled components will get grayed out automatically and cannot be interacted with by the user.
Something like this:
public class LoadingFrame extends JFrame{
JButton button;
public LoadingFrame() {
button = new JButton("ENTER");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Application entered");
}
});
setLayout(new BorderLayout());
add(button, BorderLayout.CENTER);
}
public void startLoading(){
final Component glassPane = getGlassPane();
final JPanel panel = new JPanel();
panel.setLayout(new BorderLayout());
final JLabel label = new JLabel();
panel.add(label, BorderLayout.SOUTH);
setGlassPane(panel);
panel.setVisible(true);
panel.setOpaque(false);
button.setEnabled(false);
Thread thread = new Thread(){
#Override
public void run() {
for (int i = 5; i > 0; i--) {
label.setText("Loading ... " + i);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// loading finished
setGlassPane(glassPane);
button.setEnabled(true);
}
};
thread.start();
}
public static void main(String[] args) {
LoadingFrame frame = new LoadingFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
frame.startLoading();
frame.setVisible(true);
}
}

Why slideshow not working in Java using Swing and Awt?

I am doing slideshow of images program in java using timer.
In timer event listner i have added code to chnage image but image is not changing.
Below is the code i have written
class ImagePanel extends JPanel {
private Image backgroundImage;
public ImagePanel(Image backgroundImage) {
super();
this.backgroundImage = backgroundImage;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(this.backgroundImage, 0, 0, null);
}
}
public class A extends JFrame{
static int counter;
List<String> imagePaths;
int nimgpaths=0;
static A frame = new A();
public static void main(String[] args) {
frame.setSize(1024, 768);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getPath();
/* Getting required image */
Image backgroundImage = null;
String pathToTheImage = "C:\\Documents and Settings\\Administrator\\My Documents\\My Pictures\\civ1.JPG";
try {
backgroundImage = ImageIO.read(new File(pathToTheImage));
} catch (IOException e) {
e.printStackTrace();
}
/* Initializing panel with the our image */
ImagePanel panel = new ImagePanel(backgroundImage);
frame.getContentPane().add(panel);
frame.setVisible(true);
frame.timerEvent();
//frame.show();
}
public void timerEvent(){
Timer timer = new Timer(5000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Time event occured");
if(counter > nimgpaths)
counter=0;
String imgPath=imagePaths.get(counter);
Image backgroundImage = null;
try {
backgroundImage = ImageIO.read(new File(imgPath));
}catch (Exception e1) {
e1.printStackTrace();
}
/* Initializing panel with the our image */
frame.removeAll();
ImagePanel panel = new ImagePanel(backgroundImage);
panel.repaint();
//panel.setBackground(backgroundImage);
frame.getContentPane().add(panel);
}
});
timer.start();
}
// To get path of images
public void getPath(){
DbOps db=new DbOps();
imagePaths=db.getPath();
nimgpaths=imagePaths.size();
for(Iterator i=imagePaths.iterator();i.hasNext();){
System.out.println((String)i.next());
}
}
}

Why are you using a custom panel and painting?
Your code is simply painting the image at its preferred size. This functionality is available when you use a JLabel. Then when you use the label all you need to do is use:
label.setIcon(....);
when you want to change the image. Read the section from the Swing tutorial on How to Use Icons for more information.
The only reason to create a custom component is if you plan to scale the image or do something fancy like that. If this is the case then you can use something like the Background Panel which supports scaled images as well as a setImage() method so you can change the image dynamically.

A much better design for ImagePanel would let you just replace the image, rather than removing the component. If you do have to replace a visible component, though, you have to call validate() on its container, or the new one isn't going to show up (most of the time, anyway.) I think that's your problem here.

frame.removeAll() is not doing what you would expect - it is removing the components from the frame itself rather than removing the components from the content pane of the frame. Change the code at the end of the timer's action listener to something like this to fix it:
ImagePanel panel = new ImagePanel(backgroundImage);
frame.getContentPane().removeAll();
frame.getContentPane().add(panel);
frame.getContentPane().invalidate();
frame.getContentPane().validate();

Your concept itself is wrong.
You can refresh the panel like so:
public void refreshPanel(JPanel panel){
panel.removeAll();
panel.invalidate();
panel.validate();
}
Problem:
I see in your code that you are trying to create more than one object of the same panel, which you need to refresh.
It would be better to create one panel object and refresh that object.
ImagePanel panel = new ImagePanel(backgroundImage);
Hope you can understand what I wanted to explain to you.
If you are still confused then let me know.

how to display loading dialog at center of app screen?

I want to know how to display loading dialog at center of app screen. An indefinite progress bar.

If you're talking about a JDialog, after calling pack() on it, call setLocationRelativeTo(null) to center it.

Here's how I typically show a "loading..." progress bar. The loading itself must happen on a background thread to make sure the progress bar keeps updating. The frame with the progress bar will be shown in the center of the screen.
public static void main(String[] args) throws Throwable {
final JFrame frame = new JFrame("Loading...");
final JProgressBar progressBar = new JProgressBar();
progressBar.setIndeterminate(true);
final JPanel contentPane = new JPanel();
contentPane.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
contentPane.setLayout(new BorderLayout());
contentPane.add(new JLabel("Loading..."), BorderLayout.NORTH);
contentPane.add(progressBar, BorderLayout.CENTER);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
Runnable runnable = new Runnable() {
public void run() {
// do loading stuff in here
// for now, simulate loading task with Thread.sleep(...)
try {
System.out.println("Doing loading in background step 1");
Thread.sleep(1000);
System.out.println("Doing loading in background step 2");
Thread.sleep(1000);
System.out.println("Doing loading in background step 3");
Thread.sleep(1000);
System.out.println("Doing loading in background step 4");
Thread.sleep(1000);
System.out.println("Doing loading in background step 5");
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// when loading is finished, make frame disappear
SwingUtilities.invokeLater(new Runnable() {
public void run() {
frame.setVisible(false);
}
});
}
};
new Thread(runnable).start();
}

display loading dialog at center of app screen.
dialog.setLocationRelativeTo(...);
An indefinite progress bar.
Read the section from the Swing tutorial on How to Use Progress Bars

From the documentation:
JProgressBar progressBar = new JProgressBar();
progressBar.setIndeterminate(true);
This will create the progress bar. To center it, you should take a look at the different kinds of layout managers in java.
Without any examples of your existing code, it's hard to give a more precise answer to your question.