public class BorderLayout
extends Object
implements LayoutManager2, Serializable
A border layout lays out a container, arranging and resizing
its components to fit in five regions:
north, south, east, west, and center.
Each region may contain no more than one component, and
is identified by a corresponding constant:
NORTH, SOUTH, EAST,
WEST, and CENTER. When adding a
component to a container with a border layout, use one of these
five constants, for example:
Panel p = new Panel();
p.setLayout(new BorderLayout());
p.add(new Button("Okay"), BorderLayout.SOUTH);
As a convenience,
BorderLayout interprets the
absence of a string specification the same as the constant
CENTER:
Panel p2 = new Panel();
p2.setLayout(new BorderLayout());
p2.add(new TextArea()); // Same as p.add(new TextArea(), BorderLayout.CENTER);
In addition, BorderLayout supports the relative
positioning constants, PAGE_START, PAGE_END,
LINE_START, and LINE_END.
In a container whose ComponentOrientation is set to
ComponentOrientation.LEFT_TO_RIGHT, these constants map to
NORTH, SOUTH, WEST, and
EAST, respectively.
For compatibility with previous releases, BorderLayout
also includes the relative positioning constants BEFORE_FIRST_LINE,
AFTER_LAST_LINE, BEFORE_LINE_BEGINS and
AFTER_LINE_ENDS. These are equivalent to
PAGE_START, PAGE_END, LINE_START
and LINE_END respectively. For
consistency with the relative positioning constants used by other
components, the latter constants are preferred.
Mixing both absolute and relative positioning constants can lead to
unpredicable results. If
you use both types, the relative constants will take precedence.
For example, if you add components using both the NORTH
and PAGE_START constants in a container whose
orientation is LEFT_TO_RIGHT, only the
PAGE_START will be layed out.
NOTE: Currently (in the Java 2 platform v1.2),
BorderLayout does not support vertical
orientations. The isVertical setting on the container's
ComponentOrientation is not respected.
The components are laid out according to their
preferred sizes and the constraints of the container's size.
The NORTH and SOUTH components may
be stretched horizontally; the EAST and
WEST components may be stretched vertically;
the CENTER component may stretch both horizontally
and vertically to fill any space left over.
Here is an example of five buttons in an applet laid out using
the BorderLayout layout manager:
The code for this applet is as follows:
import java.awt.*;
import java.applet.Applet;
public class buttonDir extends Applet {
public void init() {
setLayout(new BorderLayout());
add(new Button("North"), BorderLayout.NORTH);
add(new Button("South"), BorderLayout.SOUTH);
add(new Button("East"), BorderLayout.EAST);
add(new Button("West"), BorderLayout.WEST);
add(new Button("Center"), BorderLayout.CENTER);
}
}