BorderLayout (Java Platform SE 8 ) (original) (raw)

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 constantCENTER:

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 toComponentOrientation.LEFT_TO_RIGHT, these constants map toNORTH, SOUTH, WEST, andEAST, respectively.

For compatibility with previous releases, BorderLayout also includes the relative positioning constants BEFORE_FIRST_LINE,AFTER_LAST_LINE, BEFORE_LINE_BEGINS andAFTER_LINE_ENDS. These are equivalent toPAGE_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 unpredictable 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 thePAGE_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'sComponentOrientation 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 andWEST 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:

Diagram of an applet demonstrating BorderLayout.
Each section of the BorderLayout contains a Button corresponding to its position in the layout, one of:
North, West, Center, East, or South.

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); } }