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GridBagLayout Manager




GridBagLayout manager is used to position the components in rows and columns, where each row may have different number of columns. Each component added using GridBagLayout can have a different size and positioning as compared to the other components.

The location, size, alignment, height, width of each component is specified by using fields provided by GridBagLayout constraints, where constraints are object of type GridBagConstraints class.




Constructors of GridBagLayout


Constructor Description
public GridBagLayout() Creates a GridBagLayout manager.





Fields of GridBagConstraints class


GridBagLayout Constraints Description
int anchor Specifies the location of a component within a cell. Some of the values it can take -
GridBagConstraints.CENTER
GridBagConstraints.WEST
GridBagConstraints.EAST
GridBagConstraints.SOUTH
GridBagConstraints.NORTH
int gridx Specifies the X-Coordinate to which a component will be added.
int gridy Specifies the Y-Coordinate to which a component will be added
int ipadx Specifies the extra horizontal space around the component.
int ipady Specifies the extra vertical space around the component.
int gridheight Specifies the height of the component.
int gridwidth Specifies the width of the component. It can take values : GridBagConstraints.RELATIVE
GridBagConstraints.REMAINDER
int fill Specifies how a component is resized, if it is small the size of cell. It can take values of - GridBagConstraints.NONE
GridBagConstraints.HORIZONTAL
GridBagConstraints.VERTICAL
GridBagConstraints.BOTH





A few GridLayout methods


Methods Description
public void setConstraints(Component comp, GridBagConstraints cons) This method sets the constraints cons to a Component, comp
public GridBagConstraints getConstraints(Component comp) This method gets the constraints applied to a Component, comp

LayoutManager is an interface which is implemented by GridBagLayout manager class.


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An example display the use of GridBagLayout Manager.



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


class GridBagLayoutEx implements Runnable
{
public static void main(String... ar)
{
SwingUtilities.invokeLater(new SwingEx());
}

public void run()
{
new A();
}
}


class A 
{
JFrame jf;
JPanel jpp;
GridBagLayout grid;
GridBagConstraints constraints;

A()
{
jpp = new JPanel();
grid = new GridBagLayout();
constraints = new GridBagConstraints();

jf = new JFrame("GridBagLayout Example");


JButton button1 = new JButton("Button1");
JButton button2 = new JButton("Button2");
JButton button3 = new JButton("Button3");
JButton button4 = new JButton("Button4");
JButton button5 = new JButton("Button5");
JButton button6 = new JButton("Button6");

//Setting the positioning of the components in JFrame to GridBagLayout
jf.setLayout(grid);

//Padding with horizontal space of 100 pixels around the next added components
constraints.ipadx=100;

//Adding the button1 to 0th x-coordinate of 0th column, at WEST
constraints.gridx=0; 
constraints.gridy=0;
constraints.anchor =GridBagConstraints.WEST;
grid.setConstraints(button1,constraints);


//Adding the button2 to 1st x-coordinate of 0th column, at EAST
constraints.gridx=1; 
constraints.gridy=0;
constraints.anchor =GridBagConstraints.EAST; 
constraints.gridwidth = GridBagConstraints.REMAINDER;
grid.setConstraints(button2, constraints);

//Padding with vertical space of 50 pixels around the next added buttons
constraints.ipady=50;


//Adding button3 to 0th x-coordinate of 1st column, at CENTER
constraints.gridx=0; 
constraints.gridy=1;
constraints.anchor =GridBagConstraints.CENTER; 
constraints.fill= GridBagConstraints.HORIZONTAL;
grid.setConstraints(button3,constraints);



//Adding button5 to 0th x-coordinate of 2nd column, at WEST
constraints.gridx=0; 
constraints.gridy=2;
constraints.fill= GridBagConstraints.NONE;
constraints.anchor =GridBagConstraints.WEST; 
grid.setConstraints(button4,constraints);


//Adding button6 to 1st x-coordinate of 2nd column, at CENTER
constraints.gridx=1; 
constraints.gridy=2;
constraints.anchor =GridBagConstraints.CENTER; 
constraints.gridwidth = GridBagConstraints.RELATIVE;
grid.setConstraints(button5,constraints);


//Adding button7 to 2nd x-coordinate of 2nd column, at EAST
constraints.gridx=2; 
constraints.gridy=2;
constraints.anchor =GridBagConstraints.EAST;
constraints.gridwidth = GridBagConstraints.REMAINDER;
grid.setConstraints(button6,constraints);


jf.add(button1);
jf.add(button2);
jf.add(button3);
jf.add(button4);
jf.add(button5);
jf.add(button6);


jf.setVisible(true);
jf.setSize(600,300);
}
}
When you run the code, you are presented a window(please refer Figure1) showing a JFrame containing 6 JButtons with different sizes distributed in 3 rows, where-


Figure 1.



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