Learning Java, 4th Edition

The JSplitPane Class

A split pane is a special container that holds two components, each in its own subpane. A splitter bar adjusts the sizes of the two subpanes. In a document viewer, for example, you might use a split pane to show a table of contents next to a page of text.

The following example uses two JLabels containing ImageIcons, like the previous example. It displays the two labels, wrapped in JScrollPanes, on either side of a JSplitPane (see Figure 17-10). You can drag the splitter bar back and forth to adjust the sizes of the two contained components.

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

    public class SplitPaneFrame {
      public static void main(String[] args) {
        String fileOne = "Piazza di Spagna.jpg";
        String fileTwo = "L1-Light.jpg";
        if (args.length > 0) fileOne = args[0];
        if (args.length > 1) fileTwo = args[1];

        JFrame frame = new JFrame("SplitPaneFrame");

        JLabel leftImage = new JLabel( new ImageIcon( fileOne ) );
        Component left = new JScrollPane(leftImage);
        JLabel rightImage = new JLabel( new ImageIcon( fileTwo ) );
        Component right = new JScrollPane(rightImage);

        JSplitPane split =
          new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, left, right);
        split.setDividerLocation(100);
        frame.getContentPane().add(split);

        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.setSize(300, 200);
        frame.setVisible(true);
      }
    }

Figure 17-10. Using a split pane