Buttons and Labels - Con't
There's even less to be said about JLabel
components. They're just text strings or images housed in a
component. There aren't any special events associated with
labels; about all you can do is specify the text's alignment,
which controls the position of the text within the label's
display area. As with buttons, JLabels can be
created with Icons if you want to create a picture
label. The following code creates some labels with different
options:
// default alignment (CENTER)
JLabel label1 = new JLabel("Lions");
// left aligned
JLabel label2 = new JLabel("Tigers", SwingConstants.LEFT);
//label with no text, default alignment
JLabel label3 = new JLabel( );
// create image icon
Icon icon = new ImageIcon("rhino.gif");
// create image label
JLabel label4 = new JLabel(icon);
// assigning text to label3
label3.setText("and Bears");
// set alignment
label3.setHorizontalAlignment(SwingConstants.RIGHT);
The alignment constants are defined in the
SwingConstants interface.
Now we've built several labels, using a variety of constructors
and several of the class's methods. To display the labels, just
add them to a container by calling the container's add(
) method.
The other characteristics you might like to set on labels, such
as changing their font or color, are accomplished using the
methods of the Component class,
JLabel's distant ancestor. For example, you can call
setFont( ) and setColor( ) on a label,
as with any other component.
Given that labels are so simple, why do we need them at all? Why
not just draw a text string directly on the container object?
Remember that a JLabel is a JComponent.
That's important; it means that labels have the normal complement
of methods for setting fonts and colors that we mentioned
earlier, as well as the ability to be managed sensibly by a
layout manager. Therefore, they're much more flexible than a text
string drawn at an absolute location within a container.
Speaking of layouts--if you use the setText( )
method to change the text of your label, the label's preferred
size may change. But the label's container will automatically lay
out its components when this happens, so you don't have to worry
about it.
Swing can interpret HTML-formatted text in JLabel
and JButton labels. The following example shows how
to create a button with HTML-formatted text:
JButton button = new JButton(
"<html>"
+ "S<font size="-1">MALL<font size="+0"> "
+ "C<font size="-1">APITALS");
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