Develop Reference

How set JLabel at center of JDialog on X? [duplicate]

I'm using the NetBeans GUI builder to handle my layout (I'm terrible with LayoutManagers) and am trying to place a simple JLabel so that it is always centered (horizontally) inside its parent JPanel. Ideally, this would maintain true even if the JPanel was resized, but if that's a crazy amount of coding than it is sufficient to just be centered when the JPanel is first created.
I'm bad enough trying to handle layouts myself, but since the NetBeans GUI Builder autogenerates immutable code, it's been impossible for me to figure out how to do this centering, and I haven't been able to find anything online to help me.
Thanks to anybody who can steer me in the right direction!

Here are four ways to center a component:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
class CenterComponent {
public static JLabel getLabel(String text) {
return getLabel(text, SwingConstants.LEFT);
}
public static JLabel getLabel(String text, int alignment) {
JLabel l = new JLabel(text, alignment);
l.setBorder(new LineBorder(Color.RED, 2));
return l;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel p = new JPanel(new GridLayout(2,2,4,4));
p.setBackground(Color.black);
p.setBorder(new EmptyBorder(4,4,4,4));
JPanel border = new JPanel(new BorderLayout());
border.add(getLabel(
"Border", SwingConstants.CENTER), BorderLayout.CENTER);
p.add(border);
JPanel gridbag = new JPanel(new GridBagLayout());
gridbag.add(getLabel("GridBag"));
p.add(gridbag);
JPanel grid = new JPanel(new GridLayout());
grid.add(getLabel("Grid", SwingConstants.CENTER));
p.add(grid);
// from #0verbose
JPanel box = new JPanel();
box.setLayout(new BoxLayout(box, BoxLayout.X_AXIS ));
box.add(Box.createHorizontalGlue());
box.add(getLabel("Box"));
box.add(Box.createHorizontalGlue());
p.add(box);
JFrame f = new JFrame("Streeeetch me..");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(p);
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
});
}
}

By using Borderlayout, you can put any of JComponents to the CENTER area. For an example, see an answer to Stack Overflow question Get rid of the gap between JPanels. This should work.

Even with BoxLayout you can achieve that:
JPanel listPane = new JPanel();
listPane.setLayout(new BoxLayout(listPane, BoxLayout.X_AXIS ));
JLabel label = new JLabel();
listPane.add(Box.createHorizontalGlue());
listPane.add(label);
listPane.add(Box.createHorizontalGlue());
mKorbel's solution is perfect for your goal. Anyway I always like to suggest BoxLayout because it's very flexible.

Mara: "thanks for your response, however the NetBeans GUI Build uses GroupLayout and this is not overridable."
Not true! Right click anywhere inside JFrame (or any other GUI container) in NetBeans GUI builder and select "Set Layout". By default is selected "Free Design", which is Group layout, but you can select any other layout including Border layout as advised by mKorbel.

There's many ways to do this, depending on the layout manager(s) you use. I suggest you read the Laying Out Components Within a Container tutorial.
I believe the following will work, regardless of layout manager:
JLabel.setHorizontalAlignment(SwingConstants.CENTER)

Wont show scrollbar [duplicate]

This question already has an answer here:
JScrollPane not appearing on JTextArea
(1 answer)
Closed 3 years ago.
The vertical scrollbar won't show. Here is my code.
The java frame shows the textarea but the scrollbar for the textarea is not showing. I'm a green programmer so I dont have much clue of what I'm doing.
What should I do to make the scrollbar show?
Please see my code and find my mistake.
I want the scrollbar to show on the JTextArea
import javax.swing.*;//imported for the frame of the chatbot
import java.awt.*;
import java.awt.event.*;
public class Bot extends JFrame{
private JTextArea Chatarea = new JTextArea(10,20);
private JTextField Chatbox = new JTextField();
private JScrollPane Scroll = new JScrollPane(Chatarea,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
public Bot(){//frame for the chatbot
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setLayout(null);
frame.setSize(600 , 600);
frame.setTitle("JAVADDY");
frame.add(Chatarea);
frame.add(Chatbox);//
//for chat area
Chatarea.setSize(560, 400);
Chatarea.setBackground(Color.YELLOW);
Chatarea.setLocation(2, 50);
Chatarea.setLineWrap(true);
Chatarea.setEditable(false);//make jtextarea uneditable
//for chat box
Chatbox.setSize(540, 30);
Chatbox.setLocation(2, 500);
//for scrolling
Scroll.setSize(1024,800);
Scroll.setVisible(true);
Chatbox.addActionListener(new ActionListener(){
//#Override
public void actionPerformed(ActionEvent arg0){
String gtext = Chatbox.getText();
Chatarea.append("You -> "+ gtext+"\n");
Chatbox.setText("");
//place algorithm here
if(gtext.contains("Hello")){
//find way to connect to database
bot("Hi");
}
else{
bot("I don't understand.");
}
}
});
}// end of frame for the chatbot
private void bot(String string){
Chatarea.append("Bot ->" +string+"\n");
}
public static void main(String[] args){
new Bot();
}
}

Question
Did you use JScrollPane.setViewport(what's inside the JScrollPane)?
Try: Scroll.setViewport(Chatarea);
What, why and how
If all JScrollPane's contents fit, then the scroll bar is hidden. When JScrollPane has many big elements inside it, a scroll bar will be shown, in order to scroll thru it.
Try this
Add many buttons or labels inside your JScrollPane to see, if the scroll bar appears, if not, we will find out why

While YoungDev offers good advice, the problem is actually here:
Chatarea.setSize(560, 400);
Don't set the size of the JTextArea, since this constrains it to never expand when it needs to. Instead set its column and row properties which constrains the visible columns and rows, but does not constrain its actual size, allowing it to expand.
And also get rid of this:
frame.setLayout(null);
as you're shooting yourself in the foot by ignoring the layout managers.

Adding JPanel to JFrame losing ability to organize components - Java

Description: I have been working on this small project in which I need to send a a specific JPanel from a class to the main JFrame based upon a parameter passed (1-4). In my main class I have a JFrame set up so I can visually check the panel being passed.
What doesn't work
Inside the "Accessor Class", I cannot seem to position the JComboBox in the middle of the Panel. Additionally, i'm not too sure I can do any kind of positioning. I implemented a button earlier with the exact same code (I replaced the JComboBox) and I couldn't resize the button either. HOWEVER... I can change the color of it.
GridBagLayout should center on default. Why is this being overridden? If you look at the picture/link provided, it shifts itself to the top center. I simply cannot move it.
Is this problem a result of the way I receive the JPanel from the class. Is there perhaps a better way I could call the panel.
Sorry for a lack of clarity. Struggling to comprehend some of the underlying concepts here in Java.
Any help is appreciated.
This is the main class
public static void main(String[] args) {
Accessor accessorOne = new Accessor(1); //Creates the Panel with param 1
JFrame frame = new JFrame("Testing");
frame.setLayout(new GridLayout(2,2));
frame.add(new JButton("Button 2"));
frame.add(new JButton("Button 3"));
frame.add(new JButton("Button 4"));
frame.add(accessorOne); //Adds the Panel to the last spot in the JFrame
frame.setSize(650, 600);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
This is the "Accessor" class that defines the panel
public class Accessor extends JPanel{
JPanel panel = new JPanel();
public Accessor(int num){
if(num == 1){
panel.setLayout(new GridBagLayout());
String[] choice1 = {"Testing One", "Testing two" };
JComboBox choiceBoxOne = new JComboBox(choice1);
choiceBoxOne.setBackground(Color.red); //These changes are correctly reflected!
panel.add(choiceBoxOne);
choiceBoxOne.setLocation(300,300); //ERROR -> Setting this value changes nothing!
add(panel);
}
// Other num options
}
}
This is the photo of the Jframe

Problem is you are using panel within class Accessor(also a panel with default layout as FlowLayout). So instead of making another panel instance, you could have just use GridBagLayout to instance of Accessor and add controls directly to Accessor instead of new panel.
Again absolute positioning works with null layouts(not recommended).
Also don't forget to use GridBagConstraints along with GridBagLayout.

How to make a Jframe containing a Jpanel scrollable?

So I have this JFrame that contains a JPanel and in there I add JLabels with information I want but since I'll be adding labels all the time at some point the text is too long to appear so I want to add a scrollbar. Basically I want to make my JFrame with a JPanel in it scrollable. I have this code but my problem is that even though the scrollbar appears but it doesnt move and doesn't really work when the text is a lot, meaning the text still gets cut out and the scrollbar is there not moving. Does anyone know how to fix this?
import javax.swing.*;
import java.awt.*;
import java.util.*;
public class Bar {
JFrame info = new JFrame("Information");
JLabel ballinf = new JLabel();
JPanel contentPane = new JPanel();
JScrollPane scrolling = new JScrollPane();
public Bar(){
contentPane.setOpaque(true);
contentPane.setBackground(Color.WHITE);
contentPane.setLayout(null);
scrolling = new JScrollPane(contentPane,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
info.add(scrolling);
info.setSize(750, 600);
info.setLocationByPlatform(true);
info.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
info.setVisible(true);
}
public void adding(int pos){
ballinf = new JLabel("Something ",JLabel.CENTER);//assume the text will be bigger here and have more info
ballinf.setSize(700, 30);
ballinf.setForeground(Color.green);
ballinf.setLocation(5, 5+pos);
contentPane.add(ballinf);
info.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
info.setVisible(true);
}
public static void main(String[] args){
Bar stats = new Bar();
stats.adding(0);
stats.adding(20);//this will be done in a for loop for more than 2 times so the text ends up to be a lot
}
}

contentPane.setLayout(null);
Don't use a null layout!!!
You need to use an appropriate layout manager. Read the section from the Swing tutorial on Layout Managers for more information and working examples. The layout manager will then determine the preferred size of the panel as you add components to the panel.
The scrollpane will then display the scrollbars when necessary.
If you dynamically add components to the panel (after the GUI is visible) then the code should be something like:
panel.add(...);
panel.revalidate();
panel.repaint();

Image/text not showing in JFrame

I want to create a Window with an image and a text so far i've got this:
public void ShowPng1() {
ImageIcon theImage = new ImageIcon("Icon_Entry_21.gif");
panel.setSize(270, 270);
JLabel label = new JLabel("Hello, World!");
JLabel imageLabel = new JLabel(theImage);
imageLabel.setOpaque(true);
panel.add(imageLabel);
panel.add(label);
panel.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.setVisible(true);
}
My panel:
private JFrame panel = new JFrame();
For some reason it won't load nor image nor text, it just pops up as a white window. What can be the problem? I've also tried changing the format to .png, didn't work.
UPDATE
import java.awt.BorderLayout;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Img {
private JFrame panel = new JFrame();
public Img(){
ShowPng1();
}
public void ShowPng1() {
ImageIcon theImage = new ImageIcon("Icon_Entry_21.gif");
panel.setSize(300, 300);
panel.setResizable(false);
JLabel label = new JLabel("Hello, World!");
JLabel imageLabel = new JLabel(theImage);
imageLabel.setOpaque(true);
panel.add(imageLabel);
panel.add(label, BorderLayout.PAGE_END);
panel.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.setVisible(true);
}
public static void main(String[] args) {
new Img();
}
}
I've managed to get this working, which is ridiculous because I can't figure out how to make it work with my program. Reimeus gave me an idea on creating this script separately, the fix and that worked. I will have to look through my entire program to see if I'm missing anything. Creating it in a separate class should work as well.

it just pops up as a white window
Sounds like you're blocking the EDT on startup. You may need to use one of Swing's concurrency mechanisms to solve it. Post a Minimal, Complete, Tested and Readable example so we can determine this for sure.
In the meantime...
You're displacing the component containing the theImage component in the BorderLayout.CENTER location
panel.add(label);
You could organize your labels so that they can appear simultaneously (placing the components at 2 different BorderLayout locations will do)
panel.add(imageLabel);
panel.add(label, BorderLayout.PAGE_END);

You should make a JPanel and add it to the frame, and then add the labels to the panel
Something like
private JPanel panel = new JPanel;
and then add it to the frame in your method calling
frame.add(panel);