GridBagDemo.java

// Fig. 22.22: GridBagDemo.java
// Demonstrating GridBagLayout.
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
import java.awt.Component;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JComboBox;

class GridBagFrame extends JFrame 
{ 
   private final GridBagLayout layout; // layout of this frame
   private final GridBagConstraints constraints; // layout's constraints
    
   // set up GUI
   public GridBagFrame()
   {
      super("GridBagLayout");
      layout = new GridBagLayout();
      setLayout(layout); // set frame layout
      constraints = new GridBagConstraints(); // instantiate constraints

      // create GUI components
      JTextArea textArea1 = new JTextArea("TextArea1", 5, 10);
      JTextArea textArea2 = new JTextArea("TextArea2", 2, 2);

      String[] names = {"Iron", "Steel", "Brass"};
      JComboBox<String> comboBox = new JComboBox<String>(names);

      JTextField textField = new JTextField("TextField");
      JButton button1 = new JButton("Button 1");
      JButton button2 = new JButton("Button 2");
      JButton button3 = new JButton("Button 3");

      // weightx and weighty for textArea1 are both 0: the default
      // anchor for all components is CENTER: the default
      constraints.fill = GridBagConstraints.BOTH;
      addComponent(textArea1, 0, 0, 1, 3);    
       
      // weightx and weighty for button1 are both 0: the default
      constraints.fill = GridBagConstraints.HORIZONTAL;
      addComponent(button1, 0, 1, 2, 1);
      
      // weightx and weighty for comboBox are both 0: the default
      // fill is HORIZONTAL
      addComponent(comboBox, 2, 1, 2, 1);             

      // button2
      constraints.weightx = 1000;  // can grow wider
      constraints.weighty = 1;     // can grow taller
      constraints.fill = GridBagConstraints.BOTH;
      addComponent(button2, 1, 1, 1, 1);
       
      // fill is BOTH for button3
      constraints.weightx = 0;
      constraints.weighty = 0;    
      addComponent(button3, 1, 2, 1, 1);
       
      // weightx and weighty for textField are both 0, fill is BOTH
      addComponent(textField, 3, 0, 2, 1);

      // weightx and weighty for textArea2 are both 0, fill is BOTH
      addComponent(textArea2, 3, 2, 1, 1);
   } // end GridBagFrame constructor

   // method to set constraints on 
   private void addComponent(Component component,
      int row, int column, int width, int height)
   {
      constraints.gridx = column; 
      constraints.gridy = row;
      constraints.gridwidth = width;
      constraints.gridheight = height;
      layout.setConstraints(component, constraints); // set constraints
      add(component); // add component
   }
} // end class GridBagFrame

public class GridBagDemo
{ 
   public static void main(String[] args)
   { 
      GridBagFrame gridBagFrame = new GridBagFrame(); 
      gridBagFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      gridBagFrame.setSize(300, 150); 
      gridBagFrame.setVisible(true); 
   } 
} // end class GridBagDemo