gridbagdemo.java

Java语言

// Demonstrating GridBagLayout.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class GridBagDemo extends JFrame { 
   private Container container;
   private GridBagLayout gbLayout;
   private GridBagConstraints gbConstraints; 
    
   public GridBagDemo()
   {
      super( "GridBagLayout" );

      container = getContentPane();
      gbLayout = new GridBagLayout();
      container.setLayout( gbLayout );   

      // instantiate gridbag constraints
      gbConstraints = new GridBagConstraints();

      JTextArea ta = new JTextArea( "TextArea1", 5, 10 );
      JTextArea tx = new JTextArea( "TextArea2", 2, 2 );
      String names[] = { "Iron", "Steel", "Brass" };
      JComboBox cb = new JComboBox( names );
      JTextField tf = new JTextField( "TextField" );
      JButton b1 = new JButton( "Button 1" );
      JButton b2 = new JButton( "Button 2" );
      JButton b3 = new JButton( "Button 3" );

      // text area
      // weightx and weighty are both 0: the default
      // anchor for all components is CENTER: the default
      gbConstraints.fill = GridBagConstraints.BOTH;
      addComponent( ta, 0, 0, 1, 3 );    
       
      // button b1
      // weightx and weighty are both 0: the default
      gbConstraints.fill = GridBagConstraints.HORIZONTAL;
      addComponent( b1, 0, 1, 2, 1 );
      
      // combo box
      // weightx and weighty are both 0: the default
      // fill is HORIZONTAL
      addComponent( cb, 2, 1, 2, 1 );             

      // button b2
      gbConstraints.weightx = 1000;  // can grow wider
      gbConstraints.weighty = 1;     // can grow taller
      gbConstraints.fill = GridBagConstraints.BOTH;
      addComponent( b2, 1, 1, 1, 1 );
       
      // button b3
      // fill is BOTH
      gbConstraints.weightx = 0;
      gbConstraints.weighty = 0;    
      addComponent( b3, 1, 2, 1, 1 );
       
      // textfield
      // weightx and weighty are both 0: fill is BOTH
      addComponent( tf, 3, 0, 2, 1 );

      // textarea
      // weightx and weighty are both 0: fill is BOTH
      addComponent( tx, 3, 2, 1, 1 );

      setSize( 300, 150 );
      show();
   }

   // addComponent is programmer defined
   private void addComponent( Component c,
      int row, int column, int width, int height )
   {
      // set gridx and gridy 
      gbConstraints.gridx = column;
      gbConstraints.gridy = row;

      // set gridwidth and gridheight
      gbConstraints.gridwidth = width;   
      gbConstraints.gridheight = height;

      // set constraints
      gbLayout.setConstraints( c, gbConstraints );  
      container.add( c );      // add component 
   }

   public static void main( String args[] )
   {
      GridBagDemo app = new GridBagDemo();

      app.addWindowListener(
         new WindowAdapter() {
            public void windowClosing( WindowEvent e )
            {
               System.exit( 0 );
            }
         }
      );
   }
}