gridbag3.java

learning java的源代码。书中每个实例都有相关的代码example。

//file: GridBag3.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GridBag3 extends JPanel {
  GridBagConstraints constraints = new GridBagConstraints(  );

  public GridBag3(  ) {
    setLayout(new GridBagLayout(  ));
    constraints.weightx = 1.0;
    constraints.weighty = 1.0;
    constraints.fill = GridBagConstraints.BOTH;
    int x, y;  // for clarity
    constraints.gridheight = 2; // span two rows
    addGB(new JButton("one"),   x = 0, y = 0);
    constraints.gridheight = 1; // set it back
    addGB(new JButton("two"),   x = 1, y = 0);
    addGB(new JButton("three"), x = 2, y = 0);
    constraints.gridwidth = 2; // span two columns
    addGB(new JButton("four"),  x = 1, y = 1);
    constraints.gridwidth = 1; // set it back
  }

  void addGB(Component component, int x, int y) {
    constraints.gridx = x;
    constraints.gridy = y;
    add(component, constraints);
  }

  public static void main(String[] args) {
    JFrame f = new JFrame("GridBag3");
    f.addWindowListener(new WindowAdapter(  ) {
      public void windowClosing(WindowEvent e) { System.exit(0); }
    });
    f.setSize(200, 200);
    f.setLocation(200, 200);
    f.setContentPane(new GridBag3(  ));
    f.setVisible(true);
  }
}