Develop Reference

Troubles with Java Swing

I have the following code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Main
{
public static void main(String[] args)
{
Window window = new Window("This is a title", 450, 350);
JButton buttonExit = new Button("Exit", 75, 25);
window.addElement(buttonExit);
window.build();
}
}
class Window // extend the current class
{
public Window window;
public JFrame frame;
public JPanel panel;
public String title;
// instantiate object with the constructor
public Window(String title, int width, int height)
{
this.frame = new JFrame(title);
this.frame.setPreferredSize(new Dimension(width, height));
this.frame.setLocationRelativeTo(null); // centers the main window relative to the center of the screen dimension
this.panel = new JPanel();
this.panel.setPreferredSize(new Dimension(width, height));
//this.panel.setLayout(new FlowLayout());
this.frame.add(panel);
}
public void build()
{
this.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.frame.pack(); // removes all unnecessary pixel space from the form
this.frame.setVisible(true);
this.frame.setSize(frame.getPreferredSize());
}
public void addElement(JButton element)
{
this.panel.add(element);
}
}
class Button extends JButton // extend the current class
{
public Button(String text, int width, int height)
{
JButton button = new JButton();
button.setPreferredSize(new Dimension(width, height));
button.setText(text);
button.setVisible(true);
new ButtonHandler(button);
}
}
class ButtonHandler implements ActionListener
{
public ButtonHandler(JButton button)
{
button.addActionListener(this);
}
public void actionPerformed(ActionEvent actionEvent) {
System.exit(0);
}
}
I have two problems with this:
The button is compressed and won't show its text
I cannot get the event handler to work and don't appear to get why
As a side note, I know that I don't specify a LayoutManager here, but I had this implemented before and it didn't solve my issue (I tried the FlowLayoutManager and the GridBagLayout [this would be my desired one, due to its flexibility]).
Can someone tell me, what I am doing wrong here? I've only worked with C# and WPF/WinForms before...

Issue 1:
Your custom Button class is-a JButton but also has-a JButton (named button) in the constructor.
The problem here is you install the ButtonHandler class to the button of the constructor, not the custom Button itself (which is referred to as this inside the constructor).
Issue 2:
When you set the [preferred] size of the JFrame property named frame (in the custom class named Window), you are not setting the frame's contents' [preferred] size, but the size of the whole JFrame, which includes the bar located at the top of the frame (which has the title of the frame).
That lets the contents of the frame to have a space less than the preferred size, because the preferred size is set to the whole frame.
I know, you are also setting the preferred size of the JPanel named panel, which is added to the frame, but when you pack the frame, then the preferred size of the frame is prioritized rather than the preferred size of the contents of the frame, so that's probably why you are seeing the button compressed.
Let me demonstrate what I mean, with a bit of code:
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TestFramePrefSz {
public static void main(final String[] args) {
SwingUtilities.invokeLater(() -> {
final JFrame frame = new JFrame("Testing JFrame preferred size");
final JPanel contents = new JPanel();
contents.setPreferredSize(new Dimension(200, 200));
frame.setPreferredSize(new Dimension(200, 200));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(contents);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
System.out.println(contents.getSize());
});
}
}
As you can see, the dimension object printed (which is the actual size of the panel) is about 184x161 rather than 200x200 requested, because the preferred size of the frame is also set to 200x200 (which includes the title of the frame etc...).
The solution, is to only set the preferred size of the contents, not the frame (in this particular scenario at least).
So you should:
Remove the line this.frame.setSize(frame.getPreferredSize()); inside the build method.
Remove the line this.frame.setPreferredSize(new Dimension(width, height)); inside the constructor of the custom class named Window.
Issue 3:
The line this.frame.setLocationRelativeTo(null); inside the constructor of the custom class named Window, is not effective in that place.
Imagine that, when you call this method, it has to determine the location of the frame to set it.
So it needs to know first of the size of the screen and then the size of the frame itself.
But what is the size of the frame at the point where you call this method? It is about 0x0. Not the preferred size as you might expect.
That makes the calculation of the frame's location to be such that the frame will not be centered at the screen.
That's because the preferred size is a property of the frame, which is a different property than the size.
So you either have to setSize prior making the call, or better to set the preferred size of the contents of the frame (ie this.panel), then call pack on the frame and finally call the method this.frame.setLocationRelativeTo(null).
Then you are free to set the frame to visible to see where it is located in the screen (ie should be centered).
So the solution is to follow a pattern like the following:
Create the frame, add the contents of the frame to it and set the contents' preferred size.
Call pack on the frame (remember this call will change the size of the frame, according to the preferred sizes of the contents of the frame or the frame's itself).
Call setLocationRelativeTo(null) on the frame.
Call setVisible(true) on the frame.
If you take a look at your code, you are instead doing:
Create the frame.
Set the preferred size of the frame.
Call setLocationRelativeTo(null) on the frame (but the size of the frame is not set yet).
Add the contents of the frame to it (ie the panel).
Call addElement which adds more content to the panel.
Call pack on the frame (remember the preferred size of the frame is set up to this point, so it will override any other preferred sizes, such as the contents' preferred size).
Call setVisible(true) on the frame.
Call setSize on the frame, with the preferred size of it. So you are overwriting the size the frame has had from step 6.

I don't know what you're using as a tutorial. I recommend the Oracle tutorial, Creating a GUI With JFC/Swing. You can skip the Netbeans section, but I recommend going through the rest of the sections.
I created the following GUI.
The Exit button works, disposing of the GUI. The X in the upper right also disposes of the GUI.
Here's the runnable example code. The explanation follows the code.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JButtonExample implements Runnable{
public static void main(String[] args) {
SwingUtilities.invokeLater(new JButtonExample());
}
private JFrame frame;
#Override
public void run() {
frame = new JFrame("This is a title");
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
exitProcedure();
}
});
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setPreferredSize(new Dimension(300, 200));
panel.setBorder(BorderFactory.createEmptyBorder(
75, 100, 75, 100));
JButton button = new JButton("Exit");
button.addActionListener(new ExitListener(this));
panel.add(button, BorderLayout.CENTER);
return panel;
}
public void exitProcedure() {
frame.setVisible(false);
frame.dispose();
System.exit(0);
}
public class ExitListener implements ActionListener {
private JButtonExample example;
public ExitListener(JButtonExample example) {
this.example = example;
}
#Override
public void actionPerformed(ActionEvent event) {
example.exitProcedure();
}
}
}
I make a call to the SwingUtilities invokeLater method from the main method. This method makes sure that the Swing components are created and executed on the Event Dispatch Thread.
I separate the JFrame code from the JPanel code. This is so I can focus on one part of the GUI at a time.
The JFrame methods have to be called in a specific order. This is the order that I use for most of my Swing applications.
The WindowListener (WindowAdapter) gives my code control over the closing of the JFrame. This will allow the Exit button actionListener to close the JFrame. A WindowListener is not a simple concept.
The JFrame defaultCloseOperation is usually set to EXIT_ON_CLOSE. In order for the WindowListener to work, I had to set the defaultCloseOperation to DO_NOTHING_ON_CLOSE.
I let the JFrame determine its own size by using the pack method.
I set the preferred size of the JPanel.
I created an empty border for the JPanel, so the JButton would expand to fill the rest of the JPanel. That's what happens to the component placed in the center of a BorderLayout.
I created an ExitListener class. Because it's an inner class, I didn't have to create a constructor or pass the JButtonExample instance. I created a constructor so you can see how it's done, and how the actionListener method can execute the exitProcedure method of the JButtonExample class.
I hope this JButton example is helpful. The WindowListener is a bit advanced for a simple example, but you can see how it's done.

How to remove minimize button and keep maximize and close button in JFrame

I want to remove only minimize button from JFrame
but want maximize and close button in JFrame title bar.
Here I am talking about removing not disabling.

I don't think removing the minimize button is a good thing. But may be you can use the setUndecorated() method to remove the title bar and window edges. And you'll have to add your own close and maximize buttons to perfom those action.
Here is an example :
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.AbstractAction;
import javax.swing.JButton;
public class Example {
public Example() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setUndecorated(true);//<---- this will disable the frame decorations
JPanel panel = new JPanel();
panel.add(new JLabel("titlebar"));
//Add button maximize
JButton button_max=new JButton("Maximize");
button_max.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
if(frame.getExtendedState() == JFrame.NORMAL) {
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
} else {
frame.setExtendedState(JFrame.NORMAL);
}
}
});
panel.add(button_max);
//Add button close
JButton button_close = new JButton(new AbstractAction("Close") {
private static final long serialVersionUID = -4901571960357967734L;
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
});
panel.add(button_close);
frame.add(panel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
new Example();
}
}
Edit :
As #peeskillet states in the comment, even with this method the window still can be resized and draged by the user. The ComponentResizer class allows to do that.
Here is a an SO post which gives a good example to use this class with Jframe.

It's a very big hack, which works only with Synthetica L&F because it provides a painted title bar. Note: this L&F is not free to use. So if you use it you must by a license.
When you use this L&F you can iterate over all component starting from root pane to find an instance of SyntheticaTitlePane. On success you can try to access the field iconifyAction using Reflection Framework and use the method Action.setEnabled(false) on it.
I have no idea how to access the standard title bar because it's native. Probably it's impossible.

Wrong getClipBounds in combination with JScrollPane

Maybe i have encountered a bug or more probably doing something wrong ;)
I try to translate the content of a user drawn JPanel using a JScrollPanel. Inside the panel the drawing i would like to access the visible area through the Graphics class getClipBounds method to improve rendering performance.
Searching on SO brings a lot results referring to JScrollPane but none is mentioning a problem with the clip bounds. Google the same.
user drawn panel
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JPanel;
public class Content extends JPanel {
#Override
protected void paintChildren(Graphics g) {
super.paintChildren(g);
// intense clip bounds dependent rendering here
System.out.println(g.getClipBounds());
}
#Override
public Dimension getPreferredSize() {
return new Dimension(2000,2000);
}
}
main frame setup
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import java.awt.BorderLayout;
public class ClipBoundsIssue {
private JFrame frame;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
ClipBoundsIssue window = new ClipBoundsIssue();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public ClipBoundsIssue() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane scrollPane = new JScrollPane();
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
Content content = new Content();
scrollPane.setViewportView(content);
}
}
to reproduce
Just run the code, move one of the scrollbars and inspect the console output of System.out. The following picture depicted scrolling the bar on the x axis.
actual System.out result
Which produced the following results
java.awt.Rectangle[x=0,y=0,width=416,height=244]
java.awt.Rectangle[x=416,y=0,width=16,height=244]
java.awt.Rectangle[x=432,y=0,width=15,height=244]
java.awt.Rectangle[x=447,y=0,width=16,height=244]
java.awt.Rectangle[x=463,y=0,width=15,height=244]
expected result
I would have expected to have the width of the bounds to keep the same. But it changes from 416 to 16.
The question now is
Does anybody know why this happens, or how it can be avoided??
discared WAs
A possible workaround would be to lookup the view port's view bounds. But if possible i would like to avoid the Content class making any such lookup. Another alternative would be to pass the information into the Content class, but this i would like to avoid as well.

I would have expected to have the width of the bounds to keep the same.
Why? It is so simple that it is hard to explain, but let me try.
When you scrolling, only small new portion if the JPanel is appearing if you scroll slowly.
The produced output is absolutely correct:
java.awt.Rectangle[x=0,y=0,width=416,height=244] Control is shown first time, you need to redraw it completely
java.awt.Rectangle[x=416,y=0,width=16,height=244] You scrolled to the right by 16 pixels, so only narrow strip of you control must be redrawn.
You must understand that these coordinates are related to your control which has size set to 2000x2000 pixels.
Try to scroll the window created with this code and you will see what I am talking about:
import javax.swing.*;
import java.awt.*;
import java.util.Random;
public class ScrollPaneRepaintDemo extends JPanel {
public ScrollPaneRepaintDemo() {
setPreferredSize(new Dimension(2000,2000));
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.add(new JScrollPane(new ScrollPaneRepaintDemo()));
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setVisible(true);
}
#Override protected void paintComponent(Graphics g) {
Rectangle clip = g.getClipBounds();
g.setColor(new Color(new Random().nextInt()));
g.fillRect(clip.x, clip.y, clip.width, clip.height);
}
}
By the way - it works so because of JPanel's internal implementation. If you extend JComponent instead, the whole viewport will be clipped. I add also that JPanel repaints completely when resizing, its optimizations are only for scrolling.

How to have FlowLayout reposition components upon resizing.

I want to put FlowLayout with lets say 5 labels inside BorderLayout as north panel (BorderLayout.NORTH), and when I resize my window/frame I want the labels to not disappear but instead move to new line.
I have been reading about min, max values and preferredLayoutSize methods. However they do not seem to help and I am still confused.
Also, I would not like to use other layout like a wrapper or something.

One of the annoying things about FlowLayout is that it doesn't "wrap" it's contents when the available horizontal space is to small.
Instead, take a look at WrapLayout, it's FlowLayout with wrapping...

The following code does exactly what you asked.
The program has a frame whose contentPane is set for BorderLayout. It contains another panel flowPanel that has a flow layout and is added to the BorderLayout.NORTH.
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class PanelFun extends JFrame {
final JPanel flowPanel;
public PanelFun() {
setPreferredSize(new Dimension(300,300));
getContentPane().setLayout(new BorderLayout());
flowPanel = new JPanel(new FlowLayout());
addLabels();
getContentPane().add(flowPanel, BorderLayout.NORTH);
addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
PanelFun.this.getContentPane().remove(flowPanel); //this statement is really optional.
PanelFun.this.getContentPane().add(flowPanel);
}
});
}
void addLabels(){
flowPanel.add(new JLabel("One"));
flowPanel.add(new JLabel("Two"));
flowPanel.add(new JLabel("Three"));
flowPanel.add(new JLabel("Four"));
flowPanel.add(new JLabel("Five"));
}
public static void main(String[] args) {
final PanelFun frame = new PanelFun();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.pack();
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
frame.setVisible(true);
}
});
}
}
So, how does it work?
The key to having the components inside flowPanel realign when the frame is resized is this piece of code
PS: Let me know if you are new to Swing and do not understand some part of the code.
addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
PanelFun.this.getContentPane().remove(flowPanel);
PanelFun.this.getContentPane().add(flowPanel);
}
});
Without this code the flowPanel will not realign its components as it is not its normal behaviour to reposition components when the containing frame is resized.
However, it is also its behaviour that when flowPanel is added to a panel, it would position components as per the available space. So, if we add the flowPanel everytime the frame resizes, the inner elements will be repositioned to use the available space.
Update:
As camickr pointed out correctly, this method will not work in case you add anything to the center (BorderLayout.CENTER)

Bring JPanel to front of other objects in java (SWING)

I want to make a loading message when an app processes, so I used a JPanel over a JTree. But when the user clicks on the JPanel, the JTree will be selected and the JPanel will go to the back. After hiding the JPanel, it never shows again. I don't know why, but it seems it never go in front of the JTree.
I need a way to bring the JPanel in front of everything. How can I do this?
EDIT: Also I must mention that I don't want a JDialog. I want to use the JPanel on top of any element to show a loading message until a process finishes.

So here you have at least two solutions. Either go with what #Geoff and #sthupahsmaht are suggesting. BTW also possible is to use JOptionPane which automatically creates a dialog for you.
The other option would be to use a GlassPane from a frame.
Or yet another option is to use JLayeredPane as #jzd suggests.
EDIT:
Example showing how to use GlassPane to capture user selections.
Try following steps:
1.Left clicking on the glass pane visible at start. See the output.
2.Right click it. This hides the glass pane.
3.Left clicking on the content pane. See the output.
4.Right click it. Go to point 1.
Enjoy.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class OverPanel extends JPanel
{
private static void createAndShowGUI()
{
final JFrame f = new JFrame();
f.setPreferredSize(new Dimension(400, 300));
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel glassPanel = new JPanel();
glassPanel.setBackground(Color.RED);
glassPanel.addMouseListener(new MouseAdapter()
{
#Override
public void mousePressed(MouseEvent e)
{
super.mousePressed(e);
System.out.println("f.getGlassPane() mousePressed");
if(e.getButton() == MouseEvent.BUTTON3)
f.getGlassPane().setVisible(false);
}
});
f.setGlassPane(glassPanel);
f.getContentPane().setBackground(Color.GREEN);
f.getContentPane().addMouseListener(new MouseAdapter()
{
#Override
public void mousePressed(MouseEvent e)
{
super.mousePressed(e);
System.out.println("f.getContentPane() mousePressed");
if(e.getButton() == MouseEvent.BUTTON3)
f.getGlassPane().setVisible(true);
}
});
f.getGlassPane().setVisible(true);
f.pack();
f.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
createAndShowGUI();
}
});
}
}
EDIT2:
If you want to have an effect of a dialog, you can achieve it by incorporating appropriately this code into my example.
JPanel panel = new JPanel(new GridLayout(0, 1));
panel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));
panel.setBackground(Color.YELLOW);
panel.add(new JLabel("I am message Label"));
panel.add(new JButton("CLOSE"));
JPanel glassPanel = new JPanel(new GridBagLayout());
glassPanel.setOpaque(false);
glassPanel.add(panel);

You need a to use a JLayeredPane for moving components in front of each other.
Here is a tutorial: How to use Layered Panes

Disabled Glass Pane might help you out.

It's not really clear how your code is organized. However, it sounds like what you might want is a modal dialog. Here's a link to a similar discussion with a number of referenced resources.
How to make a JFrame Modal in Swing java

Use JXLayer or JIDE Overlayable.

Jpanel main = new JPanel();
Jpanel a = new JPanel();
JPanel b = new Jpanel();
main.add(a);
main.add(b);
at this point the object:
a -> 0 ( index)
b -> 1 (index)
main.getComponentCount() = 2
main.setComponentZorder(b,0);
a -> 1
b -> 0;
b OVER
a DOWN

For those who have no problem using a JDialog, this is a sure way to get it to show up if you're having issues. Just make sure to control it properly if the dialog is modal, when disposing, setting focus etc.
JDialog dialog = new JDialog();
dialog.setAlwaysOnTop(true);