AWT GridBagLayout Class


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Introduction

The class GridBagLayout arranges components in a horizontal and vertical manner.

Class declaration

Following is the declaration for java.awt.GridBagLayout class:

public class GridBagLayout
   extends Object
      implements LayoutManager2, Serializable

Field

Following are the fields for java.awt.BorderLayout class:

  • double[] columnWeights -- This field holds the overrides to the column weights.

  • int[] columnWidths -- This field holds the overrides to the column minimum width.

  • protected Hashtable comptable -- This hashtable maintains the association between a component and its gridbag constraints.

  • protected GridBagConstraints defaultConstraints -- This field holds a gridbag constraints instance containing the default values, so if a component does not have gridbag constraints associated with it, then the component will be assigned a copy of the defaultConstraints.

  • protected java.awt.GridBagLayoutInfo layoutInfo -- This field holds the layout information for the gridbag.

  • protected static int MAXGRIDSIZE -- The maximum number of grid positions (both horizontally and vertically) that can be laid out by the grid bag layout.

  • protected static int MINSIZE -- The smallest grid that can be laid out by the grid bag layout.

  • protected static int PREFERREDSIZE -- The preferred grid size that can be laid out by the grid bag layout.

  • int[] rowHeights -- This field holds the overrides to the row minimum heights.

  • double[] rowWeights -- This field holds the overrides to the row weights.

Class constructors

S.N.Constructor & Description
1GridBagLayout()

Creates a grid bag layout manager.

Class methods

S.N.Method & Description
1

void addLayoutComponent(Component comp, Object constraints)

Adds the specified component to the layout, using the specified constraints object.

2

void addLayoutComponent(String name, Component comp)

Adds the specified component with the specified name to the layout.

3

protected void adjustForGravity(GridBagConstraints constraints, Rectangle r)

Adjusts the x, y, width, and height fields to the correct values depending on the constraint geometry and pads.

4

protected void AdjustForGravity(GridBagConstraints constraints, Rectangle r)

This method is obsolete and supplied for backwards compatability only; new code should call adjustForGravity instead.

5

protected void arrangeGrid(Container parent)

Lays out the grid.

6

protected void ArrangeGrid(Container parent)

This method is obsolete and supplied for backwards compatability only; new code should call arrangeGrid instead.

7

GridBagConstraints getConstraints(Component comp)

Gets the constraints for the specified component.

8

float getLayoutAlignmentX(Container parent)

Returns the alignment along the x axis.

9

float getLayoutAlignmentY(Container parent)

Returns the alignment along the y axis.

10

int[][] getLayoutDimensions()

Determines column widths and row heights for the layout grid.

11

protected java.awt.GridBagLayoutInfo getLayoutInfo(Container parent, int sizeflag)

Fills in an instance of GridBagLayoutInfo for the current set of managed children.

12

protected java.awt.GridBagLayoutInfo GetLayoutInfo(Container parent, int sizeflag)

This method is obsolete and supplied for backwards compatability only; new code should call getLayoutInfo instead.

13

Point getLayoutOrigin()

Determines the origin of the layout area, in the graphics coordinate space of the target container.

14

double[][] getLayoutWeights()

Determines the weights of the layout grid's columns and rows.

15

protected Dimension getMinSize(Container parent, java.awt.GridBagLayoutInfo info)

Figures out the minimum size of the master based on the information from getLayoutInfo().

16

protected Dimension GetMinSize(Container parent, java.awt.GridBagLayoutInfo info)

This method is obsolete and supplied for backwards compatability only; new code should call getMinSize instead.

17

void invalidateLayout(Container target)

Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.

18

void layoutContainer(Container parent)

Lays out the specified container using this grid bag layout.

19

Point location(int x, int y)

Determines which cell in the layout grid contains the point specified by (x, y).

20

protected GridBagConstraints lookupConstraints(Component comp)

Retrieves the constraints for the specified component.

21

Dimension maximumLayoutSize(Container target)

Returns the maximum dimensions for this layout given the components in the specified target container.

22

Dimension minimumLayoutSize(Container parent)

Determines the minimum size of the parent container using this grid bag layout.

23

Dimension preferredLayoutSize(Container parent)

Determines the preferred size of the parent container using this grid bag layout.

24

void removeLayoutComponent(Component comp)

Removes the specified component from this layout.

25

void setConstraints(Component comp, GridBagConstraints constraints)

Sets the constraints for the specified component in this layout.

26

String toString()

Returns a string representation of this grid bag layout's values.

Methods inherited

This class inherits methods from the following classes:

  • java.lang.Object

GridBagLayout Example

Create the following java program using any editor of your choice in say D:/ > AWT > com > tutorialspoint > gui >

AwtLayoutDemo.java
package com.tutorialspoint.gui;

import java.awt.*;
import java.awt.event.*;

public class AwtLayoutDemo {
   private Frame mainFrame;
   private Label headerLabel;
   private Label statusLabel;
   private Panel controlPanel;
   private Label msglabel;

   public AwtLayoutDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      AwtLayoutDemo  awtLayoutDemo = new AwtLayoutDemo();  
      awtLayoutDemo.showGridBagLayoutDemo();       
   }
      
   private void prepareGUI(){
      mainFrame = new Frame("Java AWT Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      headerLabel = new Label();
      headerLabel.setAlignment(Label.CENTER);
      statusLabel = new Label();        
      statusLabel.setAlignment(Label.CENTER);
      statusLabel.setSize(350,100);

      msglabel = new Label();
      msglabel.setAlignment(Label.CENTER);
      msglabel.setText("Welcome to TutorialsPoint AWT Tutorial.");

      controlPanel = new Panel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private void showGridBagLayoutDemo(){
      headerLabel.setText("Layout in action: GridBagLayout");      

      Panel panel = new Panel();
      panel.setBackground(Color.darkGray);
      panel.setSize(300,300);
      GridBagLayout layout = new GridBagLayout();

      panel.setLayout(layout);        
      GridBagConstraints gbc = new GridBagConstraints();

      gbc.fill = GridBagConstraints.HORIZONTAL;
      gbc.gridx = 0;
      gbc.gridy = 0;
      panel.add(new Button("Button 1"),gbc);

      gbc.gridx = 1;
      gbc.gridy = 0;
      panel.add(new Button("Button 2"),gbc); 

      gbc.fill = GridBagConstraints.HORIZONTAL;
      gbc.ipady = 20;   
      gbc.gridx = 0;
      gbc.gridy = 1;
      panel.add(new Button("Button 3"),gbc); 

      gbc.gridx = 1;
      gbc.gridy = 1;       
      panel.add(new Button("Button 4"),gbc);  

      gbc.gridx = 0;
      gbc.gridy = 2;      
      gbc.fill = GridBagConstraints.HORIZONTAL;
      gbc.gridwidth = 2;
      panel.add(new Button("Button 5"),gbc);  

      controlPanel.add(panel);

      mainFrame.setVisible(true);  
   }
}

Compile the program using command prompt. Go to D:/ > AWT and type the following command.

D:\AWT>javac com\tutorialspoint\gui\AwtlayoutDemo.java

If no error comes that means compilation is successful. Run the program using following command.

D:\AWT>java com.tutorialspoint.gui.AwtlayoutDemo

Verify the following output

AWT GridBagLayout
awt_layouts.htm

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