Develop Reference

Jscrollpane center aligns when label is too small

This question is very similiar to this: JScrollPane doesn't top align when there is more than enough space to show the content I tried this solution, but it does not work.
When I add a jlabel to jscrollpane, when the jlabel is small, the label becomes centered. It works normally when the scrollbar shows. Setting boxlayout does not change anything. I feel like this isn't working properly because I'm setting a perferred size to the panel? But if I remove the line panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150)); The label becomes small when there is no text, and grows to accomdate text, which I don't want. If I add the panel instead of the label, it makes the screen scrollable even though there isn't text?
This is my code:
public class Test {
// JFrame
static JFrame frame = new JFrame("Test");
//panel 1
static JPanel panel = new JPanel(new BorderLayout());
// label to display text
static JLabel label = new JLabel();
//scroll panel in main method
public static void main(String[] args) throws Exception {
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
label.setBorder(new EmptyBorder(5, 5, 5, 20));
label.setText("any text makes it centered beyond 40 lines");
//create panel
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.add(label, BorderLayout.NORTH);
panel.add(Box.createVerticalGlue());
panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150));
panel.setBorder(new EmptyBorder(5, 5, 5, 10));
JScrollPane jspanel = new JScrollPane(label, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
//jspanel.add(label, BorderLayout.CENTER);
jspanel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 70), screenSize.height-180));
jspanel.getVerticalScrollBar().setUnitIncrement(20);
jspanel.setBorder(BorderFactory.createEmptyBorder());
jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);
//panel.setPreferredSize(new Dimension(640, 480));
//frame.add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(jspanel);
frame.setSize((int)(screenSize.width*0.7), screenSize.height - 50);
frame.revalidate();
frame.pack();
frame.setVisible(true);
}
}

jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);
That will align the scrollpane in its parent container, depending on the layout manager being used. It does not affect the alignment of any component added to the scrollpane. It is not needed.
the label becomes centered
The label is sized to fill the entire space available, so you need to customize how the text of the label is painted.
If you don't want it centered then you can place it at the top using:
label.setVerticalAlignment( SwingConstants.TOP );

After reworking your code, I came up with the following GUI.
I added a call to the SwingUtilities invokeLater method. This method ensures that all Swing components are created and executed on the Event Dispatch Thread.
I eliminated all static references, except for the main method.
I reworked your code into methods so I could focus on one part of the GUI at a time.
Here's the complete runnable example. This is a minimal reproducible example.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
public class JScrollPaneTestGUI implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new JScrollPaneTestGUI());
}
#Override
public void run() {
JFrame frame = new JFrame("JScrollPane Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane jspanel = createJScrollPane();
frame.add(jspanel, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
private JScrollPane createJScrollPane() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBackground(Color.YELLOW);
panel.setPreferredSize(new Dimension(400, 300));
JLabel label = new JLabel();
label.setBorder(new EmptyBorder(5, 5, 5, 20));
label.setText("any text makes it centered beyond 40 lines");
//create panel
panel.add(label, BorderLayout.NORTH);
JScrollPane jspanel = new JScrollPane(panel);
return jspanel;
}
}

JButton scale all the screen

I have the following code
JFrame frame = new JFrame("Organizer");
frame.setBounds(100, 100, 700, 700);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
JButton testbutton = new JButton("testbutton");
testbutton.setBounds(0, 0, 55, 55);
JButton testbutton2 = new JButton("tdestbutton2");
testbutton2.setBounds(55, 0, 44, 44);
frame.add(testbutton2);
frame.add(testbutton);
and the result sometimes is correct and sometimes is this
what im doing wrong?

What am I doing wrong?
Don't use setBounds(); do use a layout manager.
Invoke setVisible() after adding components to the enclosing container.
Construct and manipulate Swing GUI objects only on the event dispatch thread.
The example below adds a panel having an empty border and a GridLayout that is padded to match. For such an application, also consider JToolBar for the buttons and CardLayout for the working screens.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* #see http://stackoverflow.com/a/37366846/230513
*/
public class Test {
private static final int PAD = 50;
private void display() {
JFrame f = new JFrame("Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel p = new JPanel(new GridLayout(0, 1, PAD, PAD));
p.setBorder(BorderFactory.createEmptyBorder(PAD, PAD, PAD, PAD));
p.add(new JButton("Test Button 1"));
p.add(new JButton("Test Button 2"));
f.add(p, BorderLayout.CENTER);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Test()::display);
}
}

testbutton.setBounds(0, 0, 55, 55);
testbutton.setLocation(50, 50);
testbutton2.setBounds(55, 0, 44, 44);
testbutton2.setLocation(50, 100);
Get rid of those statement because then do nothing.
They do nothing because the default layout manager for the content pane of a JFrame is a BorderLayout. The BorderLayout will reset the size/location of each component.
The BorderLayout expects you to provide a "constraint", when you add the component to the frame. If you don't provide the constraint, then the "CENTER" is used. Only a single component can be added to the "CENTER" so only the last button added is displayed.
A simple solution to understand the basic concept of using a BorderLayout is to use:
//frame.add(testbutton2);
//frame.add(testbutton);
frame.add(testbutton2, BorderLayout.PAGE_START);
frame.add(testbutton, BorderLayout.PAGE_END);
This will display the button on two rows.
Read the Swing tutorial on Layout Managers for more information and examples. Download the demo code and modify that code will follow Swing conventions.
For example, you need to add components to the frame BEFORE you make the frame visible. So the order of the code should be:
frame.add(...);
frame.add(...);
frame.pack();
frame.setVisible(true);

Trying to add a scrollbar to a JPanel with GridLayout, but the JCheckBoxes just get made smaller instead

So I'm trying to set up a Gui in Java which holds a list of checkboxes. What determines the length of the list is the highlighted checkboxes. However, when I add more things to the list the checkboxes just get smaller to fit the panel. I've added a vertical scrollbar, but this just doesn't do anything. Is there something I have to do to stop the GridLayout from resizing what it holds or is it the wrong layout?
package darrt;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class TestForScrollBat {
public static void main(String[] args){
new TestForScrollBat();
}
public TestForScrollBat(){
JFrame frame = new JFrame();
JPanel panel = new JPanel(new GridLayout(0, 1));
JScrollPane scrollPane = new JScrollPane(panel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.setBounds(50, 30, 300, 50);
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
JLabel label = new JLabel(" Soc Categories");
JCheckBox soc1 = new JCheckBox("Blood and Lymphatic System Disorder");
JCheckBox soc2 = new JCheckBox("Cardiac Disorders");
JCheckBox soc3 = new JCheckBox("Congenital, familial and Genetic Disorders");
JButton jbtn = new JButton("Go!");
panel.add(label);
panel.add(soc1);
panel.add(soc2);
panel.add(soc3);
panel.add(jbtn);
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
}
I had it before so that it would add a scroll to this panel, but now it doesn't even do that.. It just creates a new JPanel on the JFrame

Your problem is about the following lines in your code:
scrollPane.setBounds(50, 30, 300, 50);
You should not set static sizes and locations when using layouts. You are telling a specific size and location to the scrollPane while you had add it to the center of the contentPane before. These two are in conflict.
And next problem is about this line:
frame.add(panel);
This line will detach the panel from you JScrollPane and add it directly to the contentPane of the JFrame.
By deleting/commenting these lines, your problem will be solved.

I wanted to ask about java program

I am a java programmer and i want to ask that why is my program not working:
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class Cool extends JFrame{
public void AL(){
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500 , 200);
frame.setVisible(true);
frame.setTitle("Java");
JTextArea textarea = new JTextArea();
textarea.setEditable(false);
textarea.setLineWrap(true);
JTextField field = new JTextField();
field.setText("Hi! This is the text!");
}
}
this is my main class:
#SuppressWarnings("serial")
public class Main {
public static void main(String[] args){
Cool dude = new Cool();
dude.AL();
}
}
It does not display anything just a blank JFrame.It does give the title but nothing else it has everything.

You have to add the JTextArea and the JTextField to the JFrame.

I don't see you adding the widgets to the JFrame, so why should they appear?
frame.add(textarea);
frame.add(field);

You are not adding the JTextArea nor the JTextField to the JFrame. You can do it through the method add which is inherited from Container. According to Java Docs:
Appends the specified component to the end of this container.
Code:
frame.add(textarea);
frame.add(field);

I know there are a good half-dozen answers with the same answer: you should add the elements to your frame. But I also wanted to add that you usually want to encapsulate your JTextArea inside a JScrollPane so that you can write more text that will be shown using scroll bars.
You should also make sure that you're adding your elements to a content pane with a layout manager so that the elements will get arranged in the way that you expect. Take a look at A Visual Guide to Layout Managers to familiarize yourself with the available layout managers. An additional, popular layout manager is MigLayout although it requires an external Jar file.
Below is a simple example with my suggestions:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class Cool extends JFrame {
private static final long serialVersionUID = 1L;
private JPanel contentPane;
private JTextField textField;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Cool frame = new Cool();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public Cool() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new BorderLayout(0, 0));
setContentPane(contentPane);
textField = new JTextField();
contentPane.add(textField, BorderLayout.NORTH);
textField.setColumns(30);
JScrollPane scrollPane = new JScrollPane();
contentPane.add(scrollPane, BorderLayout.CENTER);
JTextArea txtrImAText = new JTextArea();
txtrImAText.setRows(10);
txtrImAText.setColumns(30);
scrollPane.setViewportView(txtrImAText);
pack();
}
}

You forgot to add the elements to the frame:
frame.add(textarea );
frame.add(field);
Add thise lines and you will see a result.

I haven't used swing, but it seems that you have to add textarea and field to your JFrame frame.
Looking on the net i have seen this example:
frame.getContentPane().add(textarea);

You have to add text area and text field to the JFrame in AL method
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500 , 200);
frame.setVisible(true);
frame.setTitle("Java");
JTextArea textarea = new JTextArea();
textarea.setEditable(false);
textarea.setLineWrap(true);
JTextField field = new JTextField();
field.setText("Hi! This is the text!");
frame.add(textarea); // <-- here
frame.add(field);

Scroll bar not showing in JTextArea - Swing GUI

The scroll bar doesn't show. I've tried most of the codes people replied with in previous questions like this one.
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
textArea_2 = new JTextArea();
textArea_2.setRows(200);
textArea_2.setBounds(0, 22, 434, 120);
textArea_2.setEditable(false);
JScrollPane scrollv2 = new JScrollPane (textArea_2);
frame.add(scrollv2);
frame.getContentPane().add(textArea_2);
scrollv2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
frame.setVisible (true);

You are adding your JTextArea to your content pane where you should be actually adding your JScrollPane to the content pane of your JFrame. You should add the JTextArea to the content pane of the JScrollPane. Below is an example of the visible scroll bar in action:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class SimpleScrollBars extends JFrame {
private static final long serialVersionUID = 1L;
private JPanel contentPane;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SimpleScrollBars frame = new SimpleScrollBars();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public SimpleScrollBars() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new BorderLayout(0, 0));
setContentPane(contentPane);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
contentPane.add(scrollPane, BorderLayout.CENTER);
JTextArea textArea = new JTextArea(5, 15);
scrollPane.setViewportView(textArea);
pack();
}
}

The scrollbars will appear automatically when the preferred size of the text area is greater than the size of the scroll pane.
Your text area doesn't have any text to display, therefore its preferred size is (0, 0).
Also:
Don't use textArea_2.setBounds(...). This does nothing. The scrollpane has its own layout manager and will determine the appropriate size for the text area.
Don't use textArea_2.setRows(200). The 200 represents rows of text, not pixels. Your monitor can't display 200 rows of text. So use a reasonable value, like 10 or 20 depending on your application requirements.