// Fig. 22.21: GridBagFrame.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;

public class GridBagFrame extends JFrame 
{ 
   private GridBagLayout layout; // layout of this frame
   private GridBagConstraints constraints; // constraints of this layout
    
   // 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 comboBox = new JComboBox( 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; // set gridx
      constraints.gridy = row; // set gridy
      constraints.gridwidth = width; // set gridwidth
      constraints.gridheight = height; // set gridheight
      layout.setConstraints( component, constraints ); // set constraints
      add( component ); // add component
   } // end method addComponent
} // end class GridBagFrame

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