BoxLayout in Java

Introduction to BoxLayout in Java

BoxLayout is a standard layout manager that comes along with Java platform. It helps in arranging the components in a horizontal or vertical manner inside the container. In this, the arrangement of components will be as such even though we resize the frame.i.e.vertical arrangement stay vertical even if the frame resizes occurs. In other words, the components inside the container will not wrap. Unlike other layout managers, BoxLayout constructor passes the required containers to the layout manager constructor. Constructors, Methods, and Examples of BoxLayout Class will be discussed in the following sections.

Constructors of BoxLayout in Java

To implement the BoxLayout class in Java, the following constructor will be used:

• public BoxLayout(Container c, int axis)

The two arguments passed are container and axis which helps in creating the container with the axis mentioned. The two valid directions are:

1. Left to right – BoxLayout.X_AXIS
2. Top to bottom – BoxLayout.Y_AXIS

If we are passing the constructor as BoxLayout.Y_AXIS, a layout like the following figure(one column) will appear.

If we are passing the constructor as BoxLayout.X_AXIS, a layout like the following figure(one row) will appear.

Methods of BoxLayout class in Java

Below are the various methods of boxlayout class in java:

1. addLayoutComponent(Component comp, Object obj)

The purpose of this method is to add the mentioned component to the container using the constraint object specified.

Modifier and Type: Void

2. getLayoutAlignmentX(Container contnr)

This method returns the alignment of the container in the left to the right direction. i.e. X-Axis. The value can be given between 0 and 1, where 0 is the origin’s alignment, 1 is the furthest alignment away from the origin and 0.5 is the centered alignment.

Modifier and Type: Float

3. getLayoutAlignmentY(Container contnr)

This method returns the alignment of the container in the top to bottom direction. i.e. Y-Axis. The value can be given between 0 and 1, where 0 is the origin’s alignment, 1 is the furthest alignment away from the origin and 0.5 is the centered alignment.

Modifier and Type: Float

4. maximumLayoutSize(Container contnr)

This method returns the maximum value of size the target container can use to layout the containers that are added in it.

Modifier and Type: Float

5. minimumLayoutSize(Container contnr)

This method returns the minimum value of size the target container can use to layout the containers that are added in it.

Modifier and Type: Float

6. removeLayoutComponent(Component comp)

This method removes the mentioned component from the container’s layout.

7. layoutContainer(Container contnr)

This method lays the layout of the container when it is called by the Abstract Window Toolkit (AWT).

8. invalidateLayout(Containercontnr)

This method discards the cached information of the layout. In other words, it invalidates the layout.

Examples of BoxLayout class in Java

Now, let us see some examples of BoxLayout class with some of the methods explained in the above section.

Example 1: Java program to create a BoxLayout with X-Axis

//Java program to demonstrate BoxLayout with X Axis
import java.awt.*;
import javax.swing.*;
//A subclass BoxLayoutProgram that extends Frame Class
public class BoxLayoutProgram extends Frame {
Button buttons[];  //Button reference variable
//Constructor of BoxLayoutProgram
public BoxLayoutProgram ()
{
buttons = new Button [5];
for (int i = 0;i<5;i++)
{
buttons[i] = new Button ("Box" + (i + 1));
add (buttons[i]);  //adds button
}
setLayout (new BoxLayout (this, BoxLayout.X_AXIS));  //sets the layout by mentioning the axis
setSize(400,400);  //sets the width and height of the frame
setVisible(true);  //sets the GUI visible to user
}
public static void main(String args[]){
BoxLayoutProgram b=new BoxLayoutProgram();  //object of the class
}
}

Sample Output:

Here, the class created will be extended from the Frame class that is imported from java.awt. Then a layout with the mentioned content, width and height will be created with the help of constructor created.

Example 2: Java program to create a BoxLayout with Y-Axis

//Java program to demonstrate BoxLayout with Y Axis
import java.awt.*;
import javax.swing.*;
//A subclass BoxLayoutProgram that extends Frame Class
public class BoxLayoutProgram extends Frame {
Button buttons[];  //Button reference variable
//Constructor of BoxLayoutProgram
public BoxLayoutProgram ()
{
buttons = new Button [5];
for (int i = 0;i<5;i++)
{
buttons[i] = new Button ("Box" + (i + 1));
add (buttons[i]);  //adds button
}
setLayout (new BoxLayout (this, BoxLayout.Y_AXIS));  //sets the layout by mentioning the axis
setSize(400,400);  //sets the width and height of the frame
setVisible(true);  //sets the GUI visible to user
}
public static void main(String args[]){
BoxLayoutProgram b=new BoxLayoutProgram();  //object of the class
}
}

Sample Output:

The above program is similar to Example 1 except that this is creating buttons in Y-axis.

Example 3: Java program that creates buttons in both X-axis and Y-axis

//Java program that creates buttons in both X axis and Y axis
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//Class that extends JFrame Class
public class BoxLayoutXY extends JFrame
{
//Constructor
public BoxLayoutXY()
{
//helps in adding the object to the container
Container cp = getContentPane();
//sets the layout of container as FlowLayout where the components are placed in a line
cp.setLayout(new FlowLayout());
//create an object of the box class
Box hbox = Box. createHorizontalBox();
//create an object of the box class
Box vbox = Box. createVerticalBox();
//add horizontal and vertical components to the container
hbox.add(new JButton("Horizontal Button 1"));
hbox.add(new JButton("Horizontal Button 2"));
hbox.add(new JButton("Horizontal Button 3"));
vbox.add(new JButton("Vertical Button 1"));
vbox.add(new JButton("Vertical Button 2"));
vbox.add(new JButton("Vertical Button 3"));
cp.add(hbox);
cp.add(vbox);
//method similar to setsize that places the content in preferred size
pack();
//GUI visible to user
setVisible(true);
}
public static void main(String args[])
{
//calls the constructor of the class
new BoxLayoutXY();
}
}

Sample Output:

Unlike Examples 1 and 2, this program extends the JFrame class in order to implement the BoxLayout. Several other methods such as pack(), createVerticalBox are used that perform the same tasks that are present in Examples 1 and 2.

Conclusion

BoxLayout is a layout manager that helps in arranging the components of a container in the specified format. i.e. X-axis and Y-axis. In order to implement this, the constructor of the class which contains methods that perform different functionalities will be used.

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