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JButton in GridBagLayout in a JPanel

I am learning swing from past week, I have some issue with GridBagConstraints to put one button in top left corner but all other buttons in default in GridBagConstraints ?
I am using code that like not original but states the problem
import java.awt.*;
import javax.swing.*;
#SuppressWarnings("serial")
class MyPanel extends JPanel
{
JButton menu = new JButton("Menu"), button = new JButton("Puzzle");
GridBagConstraints gbc1 = new GridBagConstraints(), gbc2 = new GridBagConstraints();
private void setup()
{
gbc1.anchor = GridBagConstraints.FIRST_LINE_START;
gbc2.anchor = GridBagConstraints.CENTER;
gbc2.weightx = 1.0;
gbc2.weighty = 1.0;
}
public MyPanel()
{
this.setLayout(new GridBagLayout());
this.setup();
this.button.setPreferredSize(new Dimension(250, 140));
this.add(menu, gbc1);
this.add(button, gbc2);
}
}
#SuppressWarnings("serial")
public class Test extends JFrame
{
public Test()
{
this.setTitle("Test");
this.setContentPane(new MyPanel());
this.setResizable(false);
this.setSize(800, 600);
this.setVisible(true);
}
public static void main(String args[])
{
SwingUtilities.invokeLater(() -> new Test());
}
}
output
I want menu is top corner.
I read from here but i did not understand this Could you please explain GridBagConstraints for how to do that.
I Hope that problem is clear to understand, if not please let me know in comments.
EDIT:
#camickr suggestion works but a little problem, the Puzzle Button is not in extract center.
Thanks.

By default the GridBagLayout will display all the components centered horizontally and vertically, unless one of the components has a weightx/weighty value not equal to 0. Then that component will fill the extra space in the frame.
So if you want one component at the "top/left" and one in the "center", you need to:
use the "anchor" constraint. It will be different for both components.
the component in the center will need to use the "weightx/weighty" constraints.
However, an easer solution might be to use a combination of panels with different layout managers.
For example:
JPanel menuPanel = new JPanel( new FlowLayout(FlowLayout.LEFT) );
menuPanel.add(menuButton);
JPanel centerPanel = new JPanel( new GridBagLayout() );
centerPanel.add(puzzle, new GridBagConstraints());
frame.add(menuPanel, BorderLayout.PAGE_START);
frame.add(centerPanel, BorderLayout.CENTER);
So now the "top" of the frame will contain a panel with components displayed from the left and the "center" of the frame will contain your puzzle centered in the remaining space of the frame.
Edit:
I solved it but put gridx and gridy to 0 in center component, but i did not completely understand the setttings
Well I mentioned that you would need to use the gridx/gridy constraints. You should always use those constraints as it is very obvious what grid you want to add the component to. The examples from the tutorial always specify those values.
Using gridx/gridy both equal to 0, does not really make sense. The effect is that you have two components trying to share the same grid.
Remove the setResizable(false) statement and shrink the size of the frame to see how the button repositions itself.
It is not normal that two components share the same grid. Normally you would have the menu on the first row and the button on the second row. This will center the button horizontally in the frame and vertically in the space below the menu.
What you are doi

Layout Problem in Java - set a 20%opaque Panel on Bottom of JFrame

Well, actually I have a Layout problem in java Swing. I simply want to add a JPanel on the bottom of a Frame - a coding snipplet that might be done with every web based language in about 5 Minutes. Not so in Java. I tried to add a jPanel to a jFrame, that Contains a jContentPane, set the size of the jPanel to what I need and to repaint and revalidate the jFrame, as well as setting the LayOutManager to null.
Java shows me in this case a full-width jPanel, that fills my whole jFrame.
Therefore I tried another approach: I divided my jPanel in a fully transparent jPanel on top and a 20%opaque jPanel on the bottom. Still it didn't work out as expected.
Since then I tried to resize the child jPanels of my new Panel and the Panel as well and tried to repaint and revalidate the jFrame. Without any effect.
Despite of my efforts, java still shows me a full sized 20%opaque jPanel on the whole jFrame, that now contains another 20%opaque jPanel on Top.
I know that this whole problem is caused by the LayoutManager, Java useless per Default. However, it is not an option to set the LayoutManager to null or even change the LayoutManager of our jFrame, because that would lead us to refactor the whole functionality of our tiny app we worked on for several weeks.
public void showUndoPanel() {
System .out.println("Show Undo Panel");
JPanel myPanel = new JPanel(null);
JPanel glassPanel = new JPanel();
JPanel ContentPanel = new JPanel();
JLabel myJLabel = new JLabel("Great Job!");
myPanel.setBackground(new Color(255,122,122,100));
glassPanel.setSize(650, 550);
glassPanel.setBackground(new Color(255,122,122,100));
myPanel.add(glassPanel);
ContentPanel.setSize(650, 30);
ContentPanel.setBackground(new Color(255,122,122,20));
ContentPanel.add(myJLabel);
myPanel.revalidate();
myPanel.repaint();
undoPanel = myPanel;
myJFrame.add(undoPanel);
myJFrame.revalidate();
}
What I expected:
What it actually does:

Well, I solved the problem by using a BoxLayoutManager and a RigidArea. In case if anyone else may encounter that problem again in the future, I decided to provide the code for this simple solution.
public void showUndoPanel() {
System .out.println("Show Undo Panel");
JPanel myPanel = new JPanel(null);
JPanel glassPanel = new JPanel();
JPanel ContentPanel = new JPanel();
JLabel myJLabel = new JLabel("Great Job!");
myPanel.setBackground(new Color(255,255,255,0));
myPanel.setLayout(new BoxLayout(myPanel, BoxLayout.PAGE_AXIS));
glassPanel.setSize(650, 650);
glassPanel.setBounds(0,0,650,550);
glassPanel.setBackground(new Color(255,122,122,0));
myPanel.add(glassPanel);
myPanel.add(Box.createRigidArea(new Dimension(0,450)));
ContentPanel.setSize(650, 30);
ContentPanel.setBounds(0,750,650,30);
ContentPanel.setBackground(new Color(255,122,122,20));
ContentPanel.add(myJLabel);
myPanel.add(ContentPanel);
myPanel.revalidate();
myPanel.repaint();
undoPanel = myPanel;
myJFrame.add(undoPanel);
myJFrame.revalidate();
}
Now it behaves as expected:

BorderLyout would make it easier to implement.
Note the comments in the following mre:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Main {
private static JFrame myJFrame;
public static void main(String[] args) {
myJFrame = new JFrame();
myJFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
myJFrame.setLocationRelativeTo(null);
showUndoPanel();
myJFrame.pack();
myJFrame.setVisible(true);
}
public static void showUndoPanel() {
JPanel myPanel = new JPanel();
myPanel.setBackground(new Color(255,255,255,0));
myPanel.setLayout(new BorderLayout());
JPanel glassPanel = new JPanel(); //uses FlowLayout by default
//glassPanel.setSize(650, 650); //use preferred size
glassPanel.setPreferredSize(new Dimension(650, 650));
//glassPanel.setBounds(0,0,650,550); //no need to set bounds. bounds are set by the layout manager
glassPanel.setBackground(new Color(255,122,122,0));
myPanel.add(glassPanel, BorderLayout.CENTER);
JPanel contentPanel = new JPanel(); //uses FlowLayout by default
//contentPanel.setSize(650, 30);//use preferred size
contentPanel.setPreferredSize(new Dimension(650, 30));
//contentPanel.setBounds(0,750,650,30); //no need to set bounds. bounds are set by the layout manager
contentPanel.setBackground(new Color(255,122,122,20));
JLabel myJLabel = new JLabel("Great Job!");
contentPanel.add(myJLabel);
myPanel.add(contentPanel, BorderLayout.SOUTH);
myJFrame.add(myPanel);
}
}

Best practice to resize JScrollPane

I read some answered questions in this forum (this one for example) where it is strictly recommended to avoid the use of setXXXSize() methods to resize components in swing applications.
So, coming to my problem, i would like to know how to best resize a JScrollPane in order to avoid its parent panel to increase its size without any control.
Before writing some code, i want to describe the real situation, since i will post a "toy example".
In my JFrame i'm currently using a border layout for my content pane. At BorderLayout.CENTER there is a JPanel where i do some custom painting.
At BorderLayout.EAST there is a JPanel (say eastPanel) containing some components inside another panel (this panel will be added to eastPanel at BorderLayout.NORTH), and a JScrollPane which contains a JTable (added to eastPanel at BorderLayout.CENTER). This table will have a lot of rows.
Since i want eastPanel's height to be the same as centerPanel's height, i need some way to avoid the JScrollPane to increase its size in order to try to display as much rows as possible.
For now i wasn't be able to find another solution apart from calling setPreferredSize on the eastPanel containing the scrollpane, but i have to admit that i hate this kind of solution.
Sample Code
In this code sample i added some random labels at the north of eastPanel and inside the JScrollPane, since my purpose was to post a short sample of code.
However, the situation is very similar to the one i have described above.
I wasn't be able to solve my problem without using this "terrible" line of code :
eastPanel.setPreferredSize(new Dimension(eastPanel.getPreferredSize().width, centerPanel.getPreferredSize().height));
I would like to avoid a more complex layout for a simple situation like this. Am i missing something ? Also, is setting that empty border an acceptable way to set the size of the panel where i will do some custom painting?
Code :
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class Test
{
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
new TestFrame().setVisible(true);
}
catch(Exception exception) {
JOptionPane.showMessageDialog(null, "Fatal error while initialiing application", "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
}
}
class TestFrame extends JFrame
{
public TestFrame() {
super("Test");
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel pane = new JPanel(new BorderLayout(20, 0));
pane.setBorder(new EmptyBorder(20, 20, 20, 20));
JPanel centerPanel = new JPanel();
centerPanel.setBackground(Color.WHITE);
centerPanel.setBorder(new EmptyBorder(400, 400, 0, 0));
// centerPanel.setPreferredSize(new Dimension(400, 400));
JPanel eastPanel = new JPanel(new BorderLayout(0, 20));
JPanel labelsContainer = new JPanel(new GridLayout(0, 1));
for(int i=0;i<7;i++) labelsContainer.add(new JLabel(String.valueOf(i)));
eastPanel.add(labelsContainer, BorderLayout.NORTH);
JPanel moreLabelsContainer = new JPanel(new GridLayout(0, 1));
for(int i=7;i<70;i++) moreLabelsContainer.add(new JLabel(String.valueOf(i)));
JScrollPane scroll = new JScrollPane(moreLabelsContainer, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
eastPanel.add(scroll, BorderLayout.CENTER);
eastPanel.setPreferredSize(new Dimension(eastPanel.getPreferredSize().width, centerPanel.getPreferredSize().height));
pane.add(centerPanel, BorderLayout.CENTER);
pane.add(eastPanel, BorderLayout.EAST);
setContentPane(pane);
pack();
setLocationRelativeTo(null);
}
}
Thanks for your help !

I am not aware of a layout manager that restricts the height of the panel based on the height of a specific component in the panel.
One way is to customize the behaviour of the parent panel that contains the two child components.
The code might be something like:
#Override
public Dimension getPreferredSize()
{
Dimension d = super.getPreferredSize();
BorderLayout layout = (BorderLayout)getLayout();
Component center = layout.getLayoutComponent(BorderLayout.CENTER);
int centerHeight = center.getPreferreidSize().height;
if (d.height > centerHeight)
d.height = centerHeight;
return d;
}
This approach will allow for dynamic calculation of the height based on the component in the center.
Another option is to write you own layout manager. Then you can control this type of logic from within the layout manager.
Also, is setting that empty border an acceptable way to set the size of the panel where i will do some custom painting?
I override the getPreferredSize() to return the appropriate dimension.
By using the EmptyBorder you lose the ability to add a true Border to the panel, so I wouldn't recommend it.

Adding JScrollPane to a JTextArea in a JPanel

I am trying to add JScrollPane to my large JTextArea, but whenever I include the JScrollPane code, my whole JTextArea disappears.
public myGUI() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 1174, 656);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
contentPane.setVisible(true);
JTextArea textArea_1 = new JTextArea();
textArea_1.setBounds(203, 5, 869, 440);
textArea_1.setEditable(true);
textArea_1.setVisible(true);
contentPane.add(textArea_1);
JScrollPane scroll = new JScrollPane (textArea_1);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
contentPane.add(scroll);
}

Several problems with your code:
You're trying to add a component, here your JTextArea called textArea_1, to multiple containers, here the contentPane and the JScrollPane. You can't do this in Swing as a component can be added to only one component. Add it only to the JScrollPane and not to the contentPane, and then add the scroll pane to the GUI.
You're constraining the size of your JTextArea via setBounds which almost guarantees that the JScrollPane will not work since doing this prevents the JTextArea from expanding when it holds more text than is shown. Instead set the JScrollPane's rows and columns properties and not its bounds. This will be the number of rows and columns that it should display within the scrollpane
You're using null layouts but not specifying the size of the JScrollPane, and so it defaults to a size of [0, 0] -- and this is why your JTextArea disappears. Null layouts require complete specification of all component sizes and positions.
You're using null layouts to set up your GUI. While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
For example:
import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import javax.swing.*;
#SuppressWarnings("serial")
public class MyGuiPanel extends JPanel {
// some row and column values for our JTextArea
private static final int TXT_AREA_ROWS = 25;
private static final int TXT_AREA_COLS = 80;
// create the JTextArea, passing in the rows and columns values
private JTextArea textArea = new JTextArea(TXT_AREA_ROWS, TXT_AREA_COLS);
public MyGuiPanel() {
// create the JScrollPane, adding our JTextArea
JScrollPane scroll = new JScrollPane(textArea);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
// lets add some buttons to the bottom of the GUI just for fun
JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 0));
buttonPanel.add(new JButton("Save"));
buttonPanel.add(new JButton("Open"));
buttonPanel.add(new JButton("Delete"));
buttonPanel.add(new JButton("Exit"));
// let's add a title to the top:
JLabel title = new JLabel("This is my Applications's Title", SwingConstants.CENTER);
title.setFont(title.getFont().deriveFont(Font.BOLD, 24)); // and make
// the text
// *BIG*
// use a BorderLayout for our GUI
setLayout(new BorderLayout(5, 5));
setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
add(scroll, BorderLayout.CENTER); // add the scrollpane to the center
add(buttonPanel, BorderLayout.PAGE_END); // the button panel to the
// bottom
add(title, BorderLayout.PAGE_START); // and the title JLabel to the top
}
private static void createAndShowGui() {
// create our GUI JPanel
MyGuiPanel mainPanel = new MyGuiPanel();
// create a JFrame to add it to
JFrame frame = new JFrame("My GUI");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel); // add the GUI to the JFrame
frame.pack(); // tell the layout managers to do their work
frame.setLocationByPlatform(true);
frame.setVisible(true); // display the GUI
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
Also, if your program extends JFrame, understand that you are painting yourself in a corner by doing this, forcing you to create and display JFrames, when often more flexibility is called for. In fact, I would venture that most of the Swing GUI code that I've created and that I've seen does not extend JFrame, and in fact it is rare that you'll ever want to do this. More commonly your GUI classes will be geared towards creating JPanels, which can then be placed into JFrames or JDialogs, or JTabbedPanes, or swapped via CardLayouts, wherever needed. This will greatly increase the flexibility of your GUI coding.

You do not need setBounds for your JTextArea. Because you are using a null layout and the JScrollPane has no bounds, nothing shows up. Your JTextArea is also added to two places which would cause some problems. I would recommend any of swings layout managers. As an example using BorderLayout which is one of the easiest managers:
public mygui() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
setSize(700, 500);
setLayout(new BorderLayout());
JTextArea textArea_1 = new JTextArea();
textArea_1.setEditable(true);
JScrollPane scroll = new JScrollPane(textArea_1);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
add(scroll, BorderLayout.CENTER);
}

JAVA JScrollPane not showing up

I have a JPanel with scrollbar and i want to add a lot of JLabels to it. But the scrollbar doesnt work . I can not use the scrollbar and even after the panel is full it doesn't scroll . Here is my code :
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Scroll {
public static void main(String[] args) {
JPanel panel = new JPanel(new GridLayout(0,1));
JPanel p = new JPanel(new BorderLayout());
JScrollPane scroll = new JScrollPane(panel);
scroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
p.add(scroll, BorderLayout.NORTH);
JButton but = new JButton("OK");
p.add(but, BorderLayout.SOUTH);
but.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
panel.add(new JLabel("Some random text"));
scroll.revalidate();
p.repaint();p.revalidate();
}
});
JFrame frame = new JFrame();
frame.setSize(800,200);
frame.setVisible(true);
frame.add(p);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
}
}

Your problem seems to lie with your layout managers. I think BorderLayout behaves strangely when you don't use the BorderLayout.CENTER position. I changed the line
p.add(scroll, BorderLayout.NORTH);
to
p.add(scroll, BorderLayout.CENTER);
Then, to make the text appear from the top instead of centering, I changed the layout manager for the panel component to a BoxLayout. From:
JPanel panel = new JPanel(new GridLayout(0, 1));
to
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
This seems to have given me the functionality you want. Let me know if this fixes your issues or not!

As already suggested, you should probably use JList or JTable to implement your use case.
Regarding the issue, this is because all BorderLayout constraints except of CENTER will expand to as much space as their components occupy, even if that means that they will expand out of the screen bounds (in your case the NORTH section expands to the south after each button click).
To solve this, explicitly specify the preferred size for the components which can grow indefinitely if you add them to a non-central panel section with BorderLayout:
scroll.setPreferredSize(new Dimension(-1, 100));
I use -1 for the width here to indicate that it is not important (I could use any other value), since it will be ignored by the layout manager anyway (with BorderLayout.NORTH the component is stretched horizontally to take all the available horizontal space).