Java - Auto Scrollbar by adding more JPanels to parent JPanel

Question

I am Creating a Messenger like App just for learning. I set the layout of Parent JPanel to GridLayout for Grid.

Now i want JPanel to show ScrollBar when i add more JPanels which exceeds the size of Parent JPanel.

I tried adding it to ScrollPane but its not working Bellow is an Example image,

Sorry if my Question is not fully explained. I will try to explain it more if needed.

You have to set size of the jpanel which added to scrollpane to make it scrollable. Try set size of jpanel bigger tha the size of the scrollpane. — mstfyldz, Jan 29 '19 at 07:38
[How to Use Scroll Panes](https://docs.oracle.com/javase/tutorial/uiswing/components/scrollpane.html) — MadProgrammer, Jan 29 '19 at 07:43
"I will try to explain it more if needed." The question is clear. Please post your code to see what you tried. — c0der, Jan 29 '19 at 08:17
See an example of using `JScrollpane` [here](https://stackoverflow.com/a/50421615/3992939) — c0der, Jan 29 '19 at 08:34
BTW - on seeing that image, the first thing I think is `JList`. Use an appropriate rendering component and it could display `Message` objects easily. — Andrew Thompson, Jan 29 '19 at 08:39

score 0 · Answer 1 · answered Jan 29 '19 at 10:51

The way i see it, in your case a BoxLayout with Y_AXIS inside a BorderLayout (with a small "trick") would be more elegant. Take a look at the following SSCCE: There is a line to comment in order to answer your question, with a grid layout.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.border.LineBorder;

public class ChatFrame extends JFrame {
    static int x = 1;

    public ChatFrame() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(500, 500);
        setLocationRelativeTo(null);

        getContentPane().setLayout(new BorderLayout());
        JPanel gridPanel = new JPanel(new GridLayout(0, 1));
        // Comment the following line to see behavior with grid layout
        gridPanel.setLayout(new BoxLayout(gridPanel, BoxLayout.Y_AXIS));

        final JScrollPane sp = new JScrollPane(gridPanel);
        getContentPane().add(sp);

        final String helloWorld = "Hello world, ";
        Timer t = new Timer(1000, e -> {
            ChatPanel cp = new ChatPanel(helloWorld + (x++));
            gridPanel.add(cp);
            // Scroll to the last chat.
            sp.getVerticalScrollBar().setValue(sp.getVerticalScrollBar().getMaximum());
            gridPanel.repaint();
            gridPanel.revalidate();
        });
        t.start();
    }

    private static class ChatPanel extends JPanel {
        public ChatPanel(String chat) {
            super(new BorderLayout());
            setBorder(new LineBorder(Color.red));
            JLabel chatLabel = new JLabel(chat);
            add(chatLabel, BorderLayout.CENTER);
            // a kind of "trick"
            setMaximumSize(new Dimension(getMaximumSize().width, getPreferredSize().height));
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new ChatFrame().setVisible(true));
    }
}

Preview:

score 0 · Accepted Answer · answered Feb 03 '19 at 03:52

Everyone tried to solve my problem, but in my case it doesn't help me. So i tried every possible thing i could.

As i saw the scrollBar of JScrollPanel appears according to the size of JPanel so i tried to increase the size of JPanel and this solved my problem. Below is an example and explanation of what i said.

After adding all the JPanels into the parent JPanel, i configured the height of parent JPanel to {height of parent JPanel + (height of child JPanel * number of msgs)}

consider the following code:

msgPanel.setPreferredSize(new Dimension(268,418+(new msg().getPreferredSize().height*(msgs.length-4)));

here the -4 is the default number of JPanels that do can fit in default size of parent JPanel

Java - Auto Scrollbar by adding more JPanels to parent JPanel

2 Answers2