GridLayout

GridTest.java

   1:import java.awt.*;
   2:import javax.swing.*;
   3:
   4:public class GridTest extends JFrame {
   5:    JButton[] buttons = new JButton[5];
   6:    JLabel[] labels = new JLabel[5];
   7:    String[] strings = {"zero", "one", "two", "three", "four"};
   8:    Container contentPane;
   9:    public GridTest() {
  10:        super("GridTest");
  11:        contentPane = getContentPane();
  12:        int row = 5;
  13:        int col = 2;
  14:        contentPane.setLayout(new GridLayout(row,col));
  15:        // add labels and buttons
  16:        // the components are added from left to right, top to bottom
  17:        for(int i = 0; i < buttons.length; i++) {
  18:            // create labels and add to contentPane
  19:            labels[i] = new JLabel(strings[i], JLabel.CENTER);
  20:            contentPane.add(labels[i]);
  21:            // create buttons and add to contentPane
  22:            // Integer.toString(i) changes integer i to string
  23:            buttons[i] = new JButton(Integer.toString(i));
  24:            contentPane.add(buttons[i]);
  25:         }
  26:    }
  27:    
  28:   public static void main(String[] args) {
  29:        GridTest f = new GridTest();
  30:        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  31:        f.setSize(100,200);
  32:        f.setVisible(true);
  33:    }
  34:}

Explanation

• A GridLayout places components in a grid of cells.
• Each component takes all the available space within its cell, and each cell is exactly the same size.
• If you resize the GridLayout window, you'll see that the GridLayout changes the cell size so that the cells are as large as possible, given the space available to the container.
• The components are added from left to right, top to bottom.

Constructor

public GridLayout(int rows, int columns)
public GridLayout(int rows, int columns, int horizontalGap, int verticalGap)

• At least one of the rows and columns arguments must be nonzero.
• The horizontalGap and verticalGap arguments to the second constructor allow you to specify the number of pixels between cells.
• If you don't specify gaps, their values default to zero.

Add components

add(Componenet comp)

Insert components

add(Componenet comp, int index)

Remove components

remove(int index)

GridTest2.java

After uncomment line 17 and line 19.

   1:import java.awt.*;
   2:import javax.swing.*;
   3:
   4:public class GridTest2 extends JFrame {
   5:    JButton[] buttons = new JButton[10];
   6:    Container contentPane;
   7:    public GridTest2() {
   8:        super("GridTest2");
   9:        contentPane = getContentPane();
  10:        int row = 4, col = 3, hgap = 10, vgap = 5;
  11:        contentPane.setLayout(new GridLayout(row, col, hgap, vgap));
  12:        for(int i = 0; i < buttons.length; i++) {
  13:            buttons[i] = new JButton(Integer.toString(i));
  14:            contentPane.add(buttons[i]);
  15:         }
  16:         // add a new Button at the 4th position
  17:         // contentPane.add(new JButton("insert"), 4);
  18:         // remove the 1st button
  19:         // contentPane.remove(1);
  20:    }
  21:    
  22:   public static void main(String[] args) {
  23:        GridTest2 f = new GridTest2();
  24:        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  25:        f.setSize(250,250);
  26:        f.setVisible(true);
  27:    }
  28:}

Highlight of the program

• Use another constructor at line 11.
• add and remove components at line 17,19. The programs should be tested by uncommenting them.

GridTest3.java

   1:import java.awt.*;
   2:import javax.swing.*;
   3:
   4:public class GridTest3 extends JFrame {
   5:    JButton[] buttons = new JButton[10];
   6:    Container contentPane;
   7:    public GridTest3() {
   8:        super("GridTest3");
   9:        contentPane = getContentPane();
  10:        int row = 3;
  11:        // the layout will try to put the components in 3 rows 
  12:        contentPane.setLayout(new GridLayout(row, 0));
  13:        for(int i = 0; i < buttons.length; i++) {
  14:            buttons[i] = new JButton(Integer.toString(i));
  15:            contentPane.add(buttons[i]);
  16:         }
  17:    }
  18:    
  19:   public static void main(String[] args) {
  20:        GridTest3 f = new GridTest3();
  21:        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  22:        f.setSize(250,250);
  23:        f.setVisible(true);
  24:    }
  25:}

Highlight of the program

GridTest4.java

   1:import java.awt.*;
   2:import javax.swing.*;
   3:
   4:public class GridTest4 extends JFrame {
   5:    JButton[] buttons = new JButton[20];
   6:    Container contentPane;
   7:    public GridTest4() {
   8:        super("GridTest4");
   9:        contentPane = getContentPane();
  10:        int col = 6;
  11:        // the layout will try to put the components in 6 columns 
  12:        contentPane.setLayout(new GridLayout(0, col));
  13:        for(int i = 0; i < buttons.length; i++) {
  14:            buttons[i] = new JButton(Integer.toString(i));
  15:            contentPane.add(buttons[i]);
  16:         }
  17:    }
  18:    
  19:   public static void main(String[] args) {
  20:        GridTest4 f = new GridTest4();
  21:        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  22:        f.setSize(300,100);
  23:        f.setVisible(true);
  24:    }
  25:}

Highlight of the porgrams