From Grid Layout to GridBag Layout

Question

I am relatively new to Java Swing and I am having a little trouble understanding how Grid layouts can do certain things and if they can't, then how the gridbag layout, which is supposedly more powerful can do that.

Here is a program i tried with Grid layout

import javax.swing.*;
import java.awt.*;
//import java.awt.event.*;
public class Swing24
{
public static void main(String[] args)
{
JFrame f1= new JFrame("Grid Layout Test");

f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f1.setResizable(true);
f1.setLocation(500,200);
f1.setSize(600,600);

JPanel p1 = new JPanel();
p1.setBackground(Color.black);
f1.add(p1);


JButton b1= new JButton("Button 1");
b1.setBackground(Color.white);

JButton b2= new JButton("Button 2");
b2.setBackground(Color.white);

JButton b3= new JButton("Button 3");
b3.setBackground(Color.white);

JLabel lb1=new JLabel(" Label 1");
lb1.setForeground(Color.orange);
//lb1.setOpaque(true);
lb1.setBackground(Color.yellow);

JLabel lb2=new JLabel(" Label 2");
lb2.setBackground(Color.orange);
lb2.setOpaque(true);


GridLayout glm1=new GridLayout(2,3,0,0); 
p1.setLayout(glm1);

p1.add(b1);
p1.add(b2);
p1.add(b3);
p1.add(lb1);
p1.add(lb2);


f1.setVisible(true);

}
}

The above program allows me divide the container into 2 rows and 3 columns. Basically I can divide a container into m rows and n columns with a grid layout. But it adds the components(the butons and labels) serially.

Question 1: How can I directly add a button to the cell(4,3) in a grid of size(10,10)? Question 2: Can a button occupy multiple cells in a grid layout?

If the answer to any of the above is not possible, then how can gridbag layout help solve the problem. I tried using gridbag layout with a button. But it gets placed in the center! How can I, say, place it to the cell(4,3) in a container which can be divided into size(10,10)<10 rows and 10 columns>

Answer 1

1) You can't add component to specific cell,but inthat question you can find some type of trick for that.

2)Here is another trick with nested lyout inside cells, for merging.

You can do all what you want with help of GridBagLayout. Watch GridBagConstraints it helps you to layout components properly.

See properties of GridBagConstraints:

gridwidth, gridheight, gridx, gridy, anchor.

But you would need some trick with empty spaces around cell(4,3) , if you want to add only one component to your container.

Also read tutorial for GridBagLayout.

EDIT: you can try something like this

public class Form extends JFrame {

    public Form() {
        getContentPane().setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 0;
        c.weightx = 1;
        c.weighty = 1;
        for(int i =0;i<10;i++){
            c.gridx = i;
            for(int j =0;j<10;j++){
                c.gridy = j;
                if(i == 3 && j == 2){
                    c.fill = GridBagConstraints.NONE;
                    getContentPane().add(new JButton("btn"),c);
                } else {
                    c.fill = GridBagConstraints.BOTH;
                    JPanel p = new JPanel();
                    p.setBorder(BorderFactory.createLineBorder(Color.red));
                    getContentPane().add(p,c);
                }
            }
        }

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);
    }


    public static void main(String[] args) throws Exception {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                new Form().setVisible(true);
            }
        });
    }   
}

EDIT2: It's not realy cell(4,3) but in same proportions

public Form() {
    getContentPane().setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = 0;
    c.weightx = 0.2;
    c.weighty = 0.3;
    c.fill = GridBagConstraints.BOTH;
    getContentPane().add(new JLabel(" "),c);

    c.gridx++;
    c.gridy++;
    c.fill = GridBagConstraints.NONE;
    getContentPane().add(new JButton("btn"),c);

    c.weightx = 0.7;
    c.weighty = 0.6;
    c.gridx++;
    c.gridy++;
    c.fill = GridBagConstraints.BOTH;
    getContentPane().add(new JLabel(" "),c);

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    pack();
    setLocationRelativeTo(null);
}

or real cell(4,3), but more then 3 components and less then 100:

public Form() {
    getContentPane().setLayout(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    c.gridx = 0;
    c.gridy = 0;
    c.weightx = 1;
    c.weighty = 1;
    for(int i =0;i<2;i++){
        getContentPane().add(new JLabel(" "),c);
        c.gridx++;
    }

    for(int i =0;i<3;i++){
        getContentPane().add(new JLabel(" "),c);
        c.gridy++;
    }

    c.gridx = 3;
    c.gridy = 4;
    getContentPane().add(new JButton("btn"),c);

    for(int i =0;i<7;i++){
        getContentPane().add(new JLabel(" "),c);
        c.gridx++;
    }

    for(int i =0;i<6;i++){
        getContentPane().add(new JLabel(" "),c);
        c.gridy++;
    }
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    pack();
    setLocationRelativeTo(null);
}