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How do I add a scrollbar to a JFrame with setLayout(null)?

I have some components which I need to use setBounds() on, hence the reason why I'm using the setLayout(null).
But some of my components are out the window(below the Y-axis). I was wondering if there is a way to add a scrollbar to navigate down the window so as to see all the remaining components. A screenshot of my window is below.
Output of my window image:

That GUI would be simple to produce using layouts. Put the component displaying the list (which looks well suited to being a JTable, given the two pieces of data per row / line) into a JScrollPane. Put the scroll pane into the CENTER of a BorderLayout. Put the red label into the PAGE_START of the border layout. Then .. oh wait, the job is done!
This is what it might look like (using a JTextArea instead of a table).
can u please post a copy of this code.
Try implementing it based on the instructions above. If there is a problem, post a minimal reproducible example of your attempt.

Since you are refering to the items in the scrolling area as components, and not as texts in a JTextArea, please have a look at the below.
import java.awt.*;
import javax.swing.*;
import java.util.Random;
public class Mainframe {
private JFrame f;
Box box;
JScrollPane scrollPane;
Random rand = new Random();
public static void main(String[] args) {
new Mainframe().go();
}
private void go() {
box = new Box(BoxLayout.Y_AXIS);
JLabel label = new JLabel("Possible Paths and Total Distances");
label.setForeground(Color.RED);
for (int i = 0; i < 200; i++) {
box.add(Box.createRigidArea(new Dimension(0, 2)));// creates space between the components
box.add(new JLabel(i + " : " + rand.nextInt(10000)));
}
scrollPane = new JScrollPane(box);
Dimension dim = new Dimension(box.getComponent(0).getPreferredSize());
scrollPane.getVerticalScrollBar().setUnitIncrement(dim.height * 2); // adjusts scrolling speed
//scrollPane.getViewport().setBackground(Color.WHITE);
f = new JFrame();
f.getContentPane().add(label, BorderLayout.NORTH);
f.getContentPane().add(scrollPane, BorderLayout.CENTER);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(640, 480);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}

CardLayout - How to Delete current card (Java Swing)

How would one delete the current card that the user is on. I know how to go through a card layout using the next and previous function, but how would one remove the current frame that the user is on? For example, if I have a program where I am currently on the 3rd panel out of 5 total panels, how would I delete the current one which is the 3rd panel. Once you remove it, the next or previous one replaces it. I do not think removecurrentlayout can be used cause I am not removing a component. For example, in the code, how would I go about delete Card 3 if I am on that.
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Container;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class CardLayoutProg {
public static void main(String[] args) {
JFrame frame = new JFrame("CardLayout");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = frame.getContentPane();
JPanel buttonPanel = new JPanel();
JButton nextButton = new JButton("Next");
buttonPanel.add(nextButton);
contentPane.add(buttonPanel, BorderLayout.SOUTH);
final JPanel cardPanel = new JPanel();
final CardLayout cardLayout = new CardLayout();
cardPanel.setLayout(cardLayout);
for (int i = 1; i <= 5; i++) {
JButton card = new JButton("Card " + i);
card.setPreferredSize(new Dimension(200, 200));
String cardName = "card" + 123123;
cardPanel.add(card, cardName);
}
contentPane.add(cardPanel, BorderLayout.CENTER);
nextButton.addActionListener(e -> cardLayout.next(cardPanel));
frame.pack();
frame.setVisible(true);
}
}

If you look at the docs for Container, you will see that it has a remove() method. Since JPanel extends Container, it also has this method. You should familiarize yourself with these API docs to find this kind of information.

Unfortunately the CardLayout does not tell you which card (JPanel) is currently being displayed.
Check out Card Layout Focus for a class that extends the CardLayout to provide this functionality.
You would use the getCurrentCard() method to access the panel currently being displayed.
Then once you get the card currently being displayed you can remove it from the parent panel using by the remove(...) method of the Container class.
You would just use the class as follows:
//final CardLayout cardLayout = new CardLayout();
final RXCardLayout cardLayout = new RXCardLayout();
The logic for your "Remove" button would be:
cardPanel.remove(cardLayout.getCurrentCard());

When you say index(3rd panel of 5 panels), you mean the name (String) of the component when it was inserted, right? I don't know any elegant way to do this, but you can try to get all the components in this container (parentComponent) and try to find the one that has the same name as your index. For example:
Component[] components = parentComponent.getComponents();
for(int i = 0; i < components.length; i++) {
if(components[i].getName().equals(index)) {
cardLayout.removeLayoutComponent(components[i]);
}
}

How to center the view by middle panel in swing

I have to build a UI with three panels, leftPanel, middlePanel and rightPanel, Panels should be aligned Horizontally
left and right panels should get the maximum and equal width as possible while the middle panel can get the minimum width as its child component required, once the panels are added view should be centered by middle panel.
I have done following test code to build the UI
import java.awt.Color;
import java.awt.GridBagLayout;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class SwingTest extends JFrame {
private static final long serialVersionUID = 1L;
public SwingTest() {
setTitle("Swing Test");
setSize(750, 350);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(getParent());
// Rule used to find the component positions, for the testing purpose
Rule rule = new Rule(Rule.HORIZONTAL, true);
rule.setPreferredWidth(10);
rule.setPreferredHeight(40);
SidePanel leftPanel = new SidePanel("Left");
SidePanel rightPanel = new SidePanel("Right");
JPanel middlePanel = new JPanel();
middlePanel.setBorder(BorderFactory.createLineBorder(Color.black));
// Add left,right and middle panel horizontally
JPanel containerPanel = new JPanel();
containerPanel.setLayout(new BoxLayout(containerPanel, BoxLayout.X_AXIS));
containerPanel.add(leftPanel);
containerPanel.add(middlePanel);
containerPanel.add(rightPanel);
// Add rule and container panel Vertically
JPanel outerPanel = new JPanel();
outerPanel.setLayout(new BoxLayout(outerPanel, BoxLayout.Y_AXIS));
outerPanel.add(rule);
outerPanel.add(containerPanel);
add(outerPanel);
}
public static void main(String[] args) {
SwingTest test = new SwingTest();
test.setVisible(true);
}
private static class SidePanel extends JPanel {
private static final long serialVersionUID = 1L;
private SidePanel(String text) {
setLayout(new GridBagLayout());
add(new JLabel(text));
}
}
}
I have used Rule class from oracle swing tutorial site, it can be used to find the position of components. get Rule.java
The problem i have is as shown in the UI screen shot, view is not get centered by middle panel, Right now the view centered as width of `left + middle panel = right panel'
I don't want to set the panel height and width manually, It should be handled by the LayoutManager itself.
What i want is middle panel has to be get centered in a way left + middle/2 = middle/2 + right panel width.
I couldn't find a way to make the middle panel to get centered to view, Could someone help me to find a solution for this?.

You need to understand how the BoxLayout works.
First space is allocated at the preferred size of each component. Then if there is extra space, that space is allocated to each component.
The middle doesn't appear to be centered because the preferred size of the right label is larger than the left label. So when the extra space is allocated the right side is larger than the left side.
This is easy to test. Just change the text of the right side panel to "LEFT".
However, that leads to another question - Why doesn't the size of the middle panel change? I don't know the answer to this. Although for some reason the default FlowLayout seems to work different than the GridBagLayout. Again you can test this by changing the layout of the middle panel to be a GridBagLayout.
If you always want the left/right panels to be the same size then you might want to consider using the Relative Layout. Using this layout the basic code would be:
RelativeLayout rl = new RelativeLayout(RelativeLayout.X_AXIS);
JPanel panel = new JPanel( rl );
panel.add(leftPanel, new Float(1));
panel.add(middle, new Float(3));
panel.add(rightPanel, new Float(1));
Now the left/right panels will be the same size independent of the components added to each panel.

Grid Layout Java

I have created a java program that shows a grid of buttons and labels and i want to know how to pit a constraint on the labels and buttons so they dont re-size when window is dragged out.. can anyone help please?
this is my gridlayout class
package JFrameTester;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class layout extends JFrame {
JButton button1,button2,button3;
JLabel label1,Label2,Label3;
public layout (){
setLayout(new GridLayout(2, 2));
button1 = new JButton ("button1");
add(button1);
label1 = new JLabel ("label1");
add(label1);
button2 = new JButton ("button1");
add(button2);
Label2 = new JLabel ("Label2");
add(Label2);
button3 = new JButton ("button1");
add(button3);
Label3 = new JLabel ("Label3");
add(Label3);
}
}
and this is my main class
public class JFrameTester {
/**
* #param args
*/
public static void main(String[] args) {
layout Lay = new layout();
Lay.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Lay.setVisible(true);
// JFrame frame = new JFrame("BUY COMPUTER");
Lay.setSize(800, 600);
//frame.pack();
// frame.setVisible(true);
Lay.addWindowListener(new MyWindowListener());
}
}

Place the labels and buttons inside a JPanel, and then add that JPanel to your GridLayout. GridLayout automatically resizes components to fit the size of the cell they are placed in and when a JFrame is resized it will adjust the components size as needed. If you place them in JPanels only the JPanel in that cell will be resized, not the components.
EDIT
In addition to that it's Java practice to name all classes with an uppercase letter, your layout should be Layout. However, the name Layout does not accurately convey the purpose of class Layout as your class is not a layout, it's a JFrame. Perhaps LayoutFrame would be a better class name.
And (this is default Java practice) variables should be camelcase, beginning with a lowercase letter and subsequent words having a capital letter e.g. thisIsAVariable. Alternatively you could use underscores which is not normal Java practice, this_is_a_varaible. Given that in Java classes generally start with a capital letter and variables start with a lowercase letter the statement layout Lay = new layout(); looks very strange and a bit confusing at first glance.

Swing BoxLayout problem with JComboBox without using setXXXSize

here's an SSCCE:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class BoxLayoutTest extends JFrame {
public BoxLayoutTest(){
JPanel main = new JPanel();
main.setLayout(new BoxLayout(main, BoxLayout.Y_AXIS));
main.setBackground(Color.red);
this.add(main);
JPanel northPanel = new JPanel();
JPanel middle = new JPanel();
middle.setLayout(new BoxLayout(middle, BoxLayout.X_AXIS));
middle.add(new JButton("FOO"));
middle.add(Box.createHorizontalGlue());
JPanel aPanel = new JPanel();
aPanel.setBackground(Color.black);
JComboBox b = new JComboBox();
//b.setPreferredSize(new Dimension(100,16)); //uncomment this to see the layout I would like to achieve
//b.setMaximumSize(new Dimension(100,16));
//middle.add(b); //uncomment this line
middle.setBackground(Color.green);
northPanel.setBackground(Color.blue);
main.add(northPanel);
main.add(middle);
main.add(Box.createVerticalGlue());
this.setSize(800,600);
this.setResizable(true);
this.setVisible(true);
}
public static void main(String[] args) {
new BoxLayoutTest();
}
}
I'm trying to refactor some classes I wrote some time ago, when I didn't know that using setXXXSize methods on components is wrong.
Using a resizable frame ,the result I want to achieve is the following:
The northPanel should stay on top and change it's size accordingly to the frame size modifications (seems to work fine)
The green panel where I put the JButton should keep the maximum dimension of the JButton and stay just below the blue panel above (this works fine if I only put JButtons inside that panel).
The problem arise if I put a JComboBox inside the green panel (try to uncomment the line in the SSCCE). I guess JComboBox hasn't a maximum size specified, so it stretches with the frame. In the previous wrong version of my code I was using setxxxSize methods on the JComboBox to limit it's dimension(try to uncomment the line on setXXXSize methods to see it).
My question are:
Is it possible to achieve the same result using BoxLayout without invoking setXXXSize() methods?
If yes, how?
Is there any other LayoutManager that can I use to get that effect?
Please put me in the right direction

JComboBox is misbehaving (the same as JTextField) in reporting an unbounded max height: should never show more than a single line. Remedy is the same: subclass and return a reasonable height
JComboBox b = new JComboBox() {
/**
* #inherited <p>
*/
#Override
public Dimension getMaximumSize() {
Dimension max = super.getMaximumSize();
max.height = getPreferredSize().height;
return max;
}
};
just for fun, here's a snippet using MigLayout (which is my personal favorite currently :-)
// two panels as placeholders
JPanel northPanel = new JPanel();
northPanel.setBackground(Color.YELLOW);
JPanel southPanel = new JPanel();
southPanel.setBackground(Color.YELLOW);
// layout with two content columns
LC layoutContraints = new LC().wrapAfter(2)
.debug(1000);
AC columnContraints = new AC()
// first column pref, followed by greedy gap
.size("pref").gap("push")
// second
.size("pref");
// three rows, top/bottom growing, middle pref
AC rowContraints = new AC()
.grow().gap().size("pref").gap().grow();
MigLayout layout = new MigLayout(layoutContraints, columnContraints,
rowContraints);
JPanel main = new JPanel(layout);
main.setBackground(Color.WHITE);
// add top spanning columns and growing
main.add(northPanel, "spanx, grow");
main.add(new JButton("FOO"));
// well-behaved combo: max height == pref height
JComboBox combo = new JComboBox() {
#Override
public Dimension getMaximumSize() {
Dimension max = super.getMaximumSize();
max.height = getPreferredSize().height;
return max;
}
};
// set a prototype to keep it from constantly adjusting
combo.setPrototypeDisplayValue("somethingaslongasIwant");
main.add(combo);
// add top spanning columns and growing
main.add(southPanel, "spanx, grow");

I have always seen using the layout managers in the jdk are not easy. They are either too simple and inflexible or the gridbaglayout is just too much trouble. Instead I started using the jgoodies form layout and never looked back since.. Have a look at it. Its very simple and easy to use. Here's a link:
http://www.jgoodies.com/freeware/forms/
Make sure you go through the white paper.
And now, we also have google providing us a WYSISWG editor for the formlayout as a plugin for eclipse. This just makes life a lot lot easier.
http://code.google.com/javadevtools/wbpro/palettes/swing_palette.html