Learning Java, 4th Edition

Borders

Any Swing component can have a decorative border. JComponent includes a method called setBorder() ; all you have to do is call it, passing it an appropriate implementation of the Border interface.

Swing provides many useful Border implementations in the javax.swing.border package. You could create an instance of one of these classes and pass it to a component’s setBorder() method, but there’s an even simpler technique.

The BorderFactory class creates any kind of border for you using static “factory” methods. Creating and setting a component’s border, then, is simple:

    JLabel labelTwo = new JLabel("I have an etched border.");
    labelTwo.setBorder(BorderFactory.createEtchedBorder());

Every component has a setBorder() method, from simple labels and buttons right up to the fancy text and table components that we cover in Chapter 18.

BorderFactory is convenient, but it does not offer every option of every border type. For example, if you want to create a raised EtchedBorder instead of the default lowered border, you’ll need to use EtchedBorder’s constructor, like this:

    JLabel labelTwo = new JLabel("I have a raised etched border.");
    labelTwo.setBorder( new EtchedBorder(EtchedBorder.RAISED) );

The Border implementation classes are listed and briefly described here:

BevelBorder

This border draws raised or lowered beveled edges, giving an illusion of depth.

SoftBevelBorder

This border is similar to BevelBorder, but thinner.

EmptyBorder

Doesn’t do any drawing, but does take up space. You can use it to give a component a little breathing room in a crowded user interface.

EtchedBorder

A lowered etched border gives the appearance of a rectangle that has been chiseled into a piece of stone. A raised etched border looks like it is standing out from the surface of the screen.

LineBorder

Draws a simple rectangle around a component. You can specify the color and width of the line in LineBorder’s constructor.

MatteBorder

A souped-up version of LineBorder. You can create a MatteBorder with a certain color and specify the size of the border on the left, top, right, and bottom of the component. MatteBorder also allows you to pass in an Icon that will be used to draw the border. This could be an image (ImageIcon) or any other implementation of the Icon interface.

TitledBorder

A regular border with a title. TitledBorder doesn’t actually draw a border; it just draws a title in conjunction with another border object. You can specify the locations of the title, its justification, and its font. This border type is particularly useful for grouping different sets of controls in a complicated interface.

CompoundBorder

A border that contains two other borders. This is especially handy if you want to enclose a component in an EmptyBorder and then put something decorative around it, such as an EtchedBorder or a MatteBorder.

The following example shows off some different border types. It’s only a sampler, though; many more border types are available. Furthermore, the example only encloses labels with borders. You can put a border around any component in Swing. The example is shown in Figure 17-6.

Figure 17-6. A bevy of borders

Here is the source code:

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

    public class Borders {
      public static void main(String[] args) {
        // create a JFrame to hold everything
        JFrame frame = new JFrame("Borders");

        // Create labels with borders.
        int center = SwingConstants.CENTER;
        JLabel labelOne = new JLabel("raised BevelBorder", center);
        labelOne.setBorder(
            BorderFactory.createBevelBorder(BevelBorder.RAISED));
        JLabel labelTwo = new JLabel("EtchedBorder", center);
        labelTwo.setBorder(BorderFactory.createEtchedBorder());
        JLabel labelThree = new JLabel("MatteBorder", center);
        labelThree.setBorder(
            BorderFactory.createMatteBorder(10, 10, 10, 10, Color.pink));
        JLabel labelFour = new JLabel("TitledBorder", center);
        Border etch = BorderFactory.createEtchedBorder();
        labelFour.setBorder(
            BorderFactory.createTitledBorder(etch, "Title"));
        JLabel labelFive = new JLabel("TitledBorder", center);
        Border low = BorderFactory.createLoweredBevelBorder();
        labelFive.setBorder(
            BorderFactory.createTitledBorder(low, "Title",
            TitledBorder.RIGHT, TitledBorder.BOTTOM));
        JLabel labelSix = new JLabel("CompoundBorder", center);
        Border one = BorderFactory.createEtchedBorder();
        Border two =
            BorderFactory.createMatteBorder(4, 4, 4, 4, Color.blue);
        labelSix.setBorder(BorderFactory.createCompoundBorder(one, two));

        // add components to the content pane
        Container c = f.getContentPane();  // unnecessary  in 5.0+
        c.setLayout(new GridLayout(3, 2));
        c.add(labelOne);
        c.add(labelTwo);
        c.add(labelThree);
        c.add(labelFour);
        c.add(labelFive);
        c.add(labelSix);

        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.pack();
        frame.setVisible(true);
      }
    }