Question

import java.awt.*;
import javax.swing.JButton;
import javax.swing.JFrame;

public class GridBagLayoutDemo {
final static boolean shouldFill = true;
final static boolean shouldWeightX = true;
final static boolean RIGHT_TO_LEFT = false;

public static void addComponentsToPane(Container pane) {
if (RIGHT_TO_LEFT) {
pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
}

JButton button;
pane.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
if (shouldFill) {
//natural height, maximum width
c.fill = GridBagConstraints.HORIZONTAL;
}

button = new JButton("Button 1");
if (shouldWeightX) {
c.weightx = 0.5;
}
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 0;
c.gridy = 0;
pane.add(button, c);

button = new JButton("Button 2");
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 0.5;
c.gridx = 1;
c.gridy = 0;
pane.add(button, c);

button = new JButton("Button 3");
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 0.5;
c.gridx = 2;
c.gridy = 0;
pane.add(button, c);

button = new JButton("Long-Named Button 4");
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 40; //make this component tall
c.weightx = 0.0;
c.gridwidth = 3;
c.gridx = 0;
c.gridy = 1;
pane.add(button, c);

button = new JButton("5");
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 0; //reset to default
c.weighty = 1.0; //request any extra vertical space
c.anchor = GridBagConstraints.PAGE_END; //bottom of space
c.insets = new Insets(10,0,0,0); //top padding
c.gridx = 1; //aligned with button 2
c.gridwidth = 2; //2 columns wide
c.gridy = 2; //third row
pane.add(button, c);
}

private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("GridBagLayoutDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Set up the content pane.
addComponentsToPane(frame.getContentPane());

//Display the window.
frame.pack();
frame.setVisible(true);
}

public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}

I need someone to go through this program and right more comments that explain a lot more Please. from top to bottom Thanks

Answer 1

First let's have a look at the output

The code creates a java swing gui with 5 buttons placed at some specific places , such as shown above.

Three buttons are at top plced size by size , the fourth one is just below the three buttons and occupies teh entire width , the last adn teh fifth one is ateh bottom right corner.

These buttons expand or collapse as per the window size , now let's have a look at the code

Go through tehc ode , everything has been explained via comments in the code below

Code

//these three libraries are needed for creating the swing gui

import java.awt.*;

import javax.swing.JButton;

import javax.swing.JFrame;

//class

public class GridBagLayoutDemo {

    //declaring some constants varibles

    final static boolean shouldFill = true;

    final static boolean shouldWeightX = true;

    final static boolean RIGHT_TO_LEFT = false;

    //method which sets up the content pane

    public static void addComponentsToPane(Container pane) {

        if (RIGHT_TO_LEFT) {

            pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);

        }

        JButton button;

        //this means that the gui will be based on grid layout

        pane.setLayout(new GridBagLayout());

        GridBagConstraints c = new GridBagConstraints();

        if (shouldFill) {

            // natural height, maximum width

            //this specifies to fill any horizontal extra space ,

            c.fill = GridBagConstraints.HORIZONTAL;

        }

        //create the first button

        button = new JButton("Button 1");

        if (shouldWeightX) {

            c.weightx = 0.5;

        }

        //this means to fill any extra horizontal space

        c.fill = GridBagConstraints.HORIZONTAL;

        c.gridx = 0;//specifies that this button will be on the first coloumn

        c.gridy = 0;///specifes the row number

        pane.add(button, c);//add the button

        //second button

        button = new JButton("Button 2");

        c.fill = GridBagConstraints.HORIZONTAL;

        c.weightx = 0.5;

        c.gridx = 1;//column

        c.gridy = 0;//row

        pane.add(button, c); //place the button

        //thirs button

        button = new JButton("Button 3");

        c.fill = GridBagConstraints.HORIZONTAL;

        c.weightx = 0.5;

        c.gridx = 2;//column

        c.gridy = 0;//row

        pane.add(button, c);

        //forth button

        button = new JButton("Long-Named Button 4");

        c.fill = GridBagConstraints.HORIZONTAL;

        c.ipady = 40; // specifies the padding that is the gaps between the button name adn its surrounding

        c.weightx = 0.0;

        c.gridwidth = 3;//this specifies it to occupy the entire width

        c.gridx = 0;//column number

        c.gridy = 1;//row number

        pane.add(button, c);

        // the fifth button

        button = new JButton("5");

        c.fill = GridBagConstraints.HORIZONTAL;

        c.ipady = 0; // reset to default

        c.weighty = 1.0; // request any extra vertical space

        c.anchor = GridBagConstraints.PAGE_END; // bottom of space

        c.insets = new Insets(10, 0, 0, 0); // top padding

        c.gridx = 1; // aligned with button 2

        c.gridwidth = 2; // 2 columns wide

        c.gridy = 2; // third row

        pane.add(button, c);

    }

    //method which creates the GUI (places 5 buttons) and rednders it

    private static void createAndShowGUI() {

        // Create and set up the window.

        JFrame frame = new JFrame("GridBagLayoutDemo");//here we create the window adn also specify the title for it

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // this is teh default behaviour that we want when close button is clicked

        // Set up the content pane.

        addComponentsToPane(frame.getContentPane());

        // Display the window.

        frame.pack();

        frame.setVisible(true); //if not provided then the window won't be visible

    }

    //this is the main driver code the program

    //it is the first method that gets invoked when the jaav application is run

    public static void main(String[] args) {

        // Schedule a job for the event-dispatching thread:

        // creating and showing this application's GUI.

        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            //runnable has a predefined method run() which is invoked at the appropriate time

            public void run() {

                //call the method to craete teh respective gui and display it

                //createAndShowGUI is a static method and hence can be called directly , without having to specify class name

                createAndShowGUI();

            }

        });

    }

}

Screenshot