java.lang.Object | |
↳ | java.awt.BorderLayout |
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); } }
Constants | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
String | AFTER_LAST_LINE | Synonym for PAGE_END. | |||||||||
String | AFTER_LINE_ENDS | Synonym for LINE_END. | |||||||||
String | BEFORE_FIRST_LINE | Synonym for PAGE_START. | |||||||||
String | BEFORE_LINE_BEGINS | Synonym for LINE_START. | |||||||||
String | CENTER | The center layout constraint (middle of container). | |||||||||
String | EAST | The east layout constraint (right side of container). | |||||||||
String | LINE_END | The component goes at the end of the line direction for the layout. | |||||||||
String | LINE_START | The component goes at the beginning of the line direction for the layout. | |||||||||
String | NORTH | The north layout constraint (top of container). | |||||||||
String | PAGE_END | The component comes after the last line of the layout's content. | |||||||||
String | PAGE_START | The component comes before the first line of the layout's content. | |||||||||
String | SOUTH | The south layout constraint (bottom of container). | |||||||||
String | WEST | The west layout constraint (left side of container). |
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Constructs a new border layout with
no gaps between components.
| |||||||||||
Constructs a border layout with the specified gaps
between components.
|
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
This method is deprecated.
replaced by
addLayoutComponent(Component, Object) .
| |||||||||||
Adds the specified component to the layout, using the specified
constraint object.
| |||||||||||
Gets the constraints for the specified component
| |||||||||||
Returns the horizontal gap between components.
| |||||||||||
Returns the alignment along the x axis.
| |||||||||||
Returns the alignment along the y axis.
| |||||||||||
Gets the component that was added using the given constraint
| |||||||||||
Returns the component that corresponds to the given constraint location
based on the target
Container 's component orientation. | |||||||||||
Returns the vertical gap between components.
| |||||||||||
Invalidates the layout, indicating that if the layout manager
has cached information it should be discarded.
| |||||||||||
Lays out the container argument using this border layout.
| |||||||||||
Returns the maximum dimensions for this layout given the components
in the specified target container.
| |||||||||||
Determines the minimum size of the
target container
using this layout manager. | |||||||||||
Determines the preferred size of the
target
container using this layout manager, based on the components
in the container. | |||||||||||
Removes the specified component from this border layout.
| |||||||||||
Sets the horizontal gap between components.
| |||||||||||
Sets the vertical gap between components.
| |||||||||||
Returns a string representation of the state of this border layout.
|
[Expand]
Inherited Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.lang.Object
| |||||||||||
From interface
java.awt.LayoutManager
| |||||||||||
From interface
java.awt.LayoutManager2
|
Synonym for PAGE_END. Exists for compatibility with previous versions. PAGE_END is preferred.
Synonym for LINE_END. Exists for compatibility with previous versions. LINE_END is preferred.
Synonym for PAGE_START. Exists for compatibility with previous versions. PAGE_START is preferred.
Synonym for LINE_START. Exists for compatibility with previous versions. LINE_START is preferred.
The center layout constraint (middle of container).
The east layout constraint (right side of container).
The component goes at the end of the line direction for the layout. For Western, left-to-right and top-to-bottom orientations, this is equivalent to EAST.
The component goes at the beginning of the line direction for the layout. For Western, left-to-right and top-to-bottom orientations, this is equivalent to WEST.
The north layout constraint (top of container).
The component comes after the last line of the layout's content. For Western, left-to-right and top-to-bottom orientations, this is equivalent to SOUTH.
The component comes before the first line of the layout's content. For Western, left-to-right and top-to-bottom orientations, this is equivalent to NORTH.
The south layout constraint (bottom of container).
The west layout constraint (left side of container).
Constructs a new border layout with no gaps between components.
Constructs a border layout with the specified gaps
between components.
The horizontal gap is specified by hgap
and the vertical gap is specified by vgap
.
hgap | the horizontal gap. |
---|---|
vgap | the vertical gap. |
This method is deprecated.
replaced by addLayoutComponent(Component, Object)
.
If the layout manager uses a per-component string,
adds the component comp
to the layout,
associating it
with the string specified by name
.
name | the string to be associated with the component |
---|---|
comp | the component to be added |
Adds the specified component to the layout, using the specified
constraint object. For border layouts, the constraint must be
one of the following constants: NORTH
,
SOUTH
, EAST
,
WEST
, or CENTER
.
Most applications do not call this method directly. This method
is called when a component is added to a container using the
Container.add
method with the same argument types.
comp | the component to be added. |
---|---|
constraints | an object that specifies how and where the component is added to the layout. |
IllegalArgumentException | if the constraint object is not a string, or if it not one of the five specified constants. |
---|
Gets the constraints for the specified component
comp | the component to be queried |
---|
Returns the horizontal gap between components.
Returns the alignment along the x axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.
Returns the alignment along the y axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.
Gets the component that was added using the given constraint
constraints | the desired constraint, one of CENTER ,
NORTH , SOUTH ,
WEST , EAST ,
PAGE_START , PAGE_END ,
LINE_START , LINE_END |
---|
null
if
the location is emptyIllegalArgumentException | if the constraint object is not one of the nine specified constants |
---|
Returns the component that corresponds to the given constraint location
based on the target Container
's component orientation.
Components added with the relative constraints PAGE_START
,
PAGE_END
, LINE_START
, and LINE_END
take precedence over components added with the explicit constraints
NORTH
, SOUTH
, WEST
, and EAST
.
The Container
's component orientation is used to determine the location of components
added with LINE_START
and LINE_END
.
target | the Container used to obtain
the constraint location based on the target
Container 's component orientation. |
---|---|
constraints | the desired absolute position, one of CENTER ,
NORTH , SOUTH ,
EAST , WEST |
null
if
the location is emptyIllegalArgumentException | if the constraint object is not one of the five specified constants |
---|---|
NullPointerException | if the target parameter is null |
Returns the vertical gap between components.
Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
Lays out the container argument using this border layout.
This method actually reshapes the components in the specified
container in order to satisfy the constraints of this
BorderLayout
object. The NORTH
and SOUTH
components, if any, are placed at
the top and bottom of the container, respectively. The
WEST
and EAST
components are
then placed on the left and right, respectively. Finally,
the CENTER
object is placed in any remaining
space in the middle.
Most applications do not call this method directly. This method
is called when a container calls its doLayout
method.
target | the container in which to do the layout. |
---|
Returns the maximum dimensions for this layout given the components in the specified target container.
target | the component which needs to be laid out |
---|
Determines the minimum size of the target
container
using this layout manager.
This method is called when a container calls its
getMinimumSize
method. Most applications do not call
this method directly.
target | the container in which to do the layout. |
---|
Determines the preferred size of the target
container using this layout manager, based on the components
in the container.
Most applications do not call this method directly. This method
is called when a container calls its getPreferredSize
method.
target | the container in which to do the layout. |
---|
Removes the specified component from this border layout. This
method is called when a container calls its remove
or
removeAll
methods. Most applications do not call this
method directly.
comp | the component to be removed. |
---|
Sets the horizontal gap between components.
hgap | the horizontal gap between components |
---|
Sets the vertical gap between components.
vgap | the vertical gap between components |
---|
Returns a string representation of the state of this border layout.