How to set button size using JPanel

Question

I am creating a button and label in JPanel. This panel i am adding to a JScrollPane which is eventually added to a frame. Here is my code.

public static void main(String[] args) {

    final JFrame frame = new JFrame();
    JPanel Jpanel =new JPanel(new GridLayout(0, 1));
    JScrollPane pane = new JScrollPane(Jpanel,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

    frame.setSize(500, 500);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    JLabel n = new JLabel("hifadfad");
    n.setBounds(90, 20, 100, 100);
    Jpanel.add(n);

    JButton b = new JButton("hi");
    b.setBounds(10, 40, 60, 60);
    Jpanel.add(b);

    frame.add(pane);
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            frame.setVisible(true);
        }
    });
}

After i run, i get something like this

How should i set the size of this button ?

Thanks for the help. Appreciate :)

Answer 1

Start by having a look at Laying Out Components Within a Container, which will provide with more information about how Swing handles component placement and sizing.

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            JLabel lbl = new JLabel("Welcome");
            JButton btn = new JButton("Hi");

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;

            add(lbl, gbc);
            add(btn, gbc);
        }

    }

}

Answer 2

This is problem is rather complicated to solve, but there are several options:

1. use a GridBagLayout. This will allow you (in a limited way) to specify size and position of the single elements
2. generate your own layoutmanager matching your constraints.
3. This isn't exactly a nice solution: remove the layoutmanager from the panel and set the position and size of all elements manually. Note that this requires you aswell to specify the preferred size (in some cases even the minimum size) of the panel, since otherwise the panel won't be shown in the scrollpane (size = (0 , 0)).

Just experimentate a bit with the single options. Note that solution 3 is rather mentioned for completeness than because you should use it.

Answer 3

Put in your code

Jpanel.setLayout(null);