java.lang.Object java.awt.BorderLayout
public class 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); } }
Container.add(String, Component)
, ComponentOrientation
, Serialized Form
BorderLayout()
BorderLayout(int hgap, int vgap)
public static final String NORTH
public static final String SOUTH
public static final String EAST
public static final String WEST
public static final String CENTER
public static final String BEFORE_FIRST_LINE
PAGE_START
, Constant Field Values
public static final String AFTER_LAST_LINE
PAGE_END
, Constant Field Values
public static final String BEFORE_LINE_BEGINS
LINE_START
, Constant Field Values
public static final String AFTER_LINE_ENDS
LINE_END
, Constant Field Values
public static final String PAGE_START
Component.getComponentOrientation()
, Constant Field Values
public static final String PAGE_END
Component.getComponentOrientation()
, Constant Field Values
public static final String LINE_START
Component.getComponentOrientation()
, Constant Field Values
public static final String LINE_END
Component.getComponentOrientation()
, Constant Field Values
public BorderLayout()
public BorderLayout(int hgap, int vgap)
hgap
and the vertical gap is specified by vgap
.
hgap
- the horizontal gap.
vgap
- the vertical gap.
public int getHgap()
public void setHgap(int hgap)
hgap
- the horizontal gap between components
public int getVgap()
public void setVgap(int vgap)
vgap
- the vertical gap between components
public void addLayoutComponent(Component comp, Object constraints)
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.
addLayoutComponent
in interface LayoutManager2
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.
Container.add(java.awt.Component, java.lang.Object)
@Deprecated public void addLayoutComponent(String name, Component comp)
addLayoutComponent(Component, Object)
.
LayoutManager
comp
to the layout, associating it with the string specified by name
.
addLayoutComponent
in interface LayoutManager
name
- the string to be associated with the component
comp
- the component to be added
public void removeLayoutComponent(Component comp)
remove
or removeAll
methods. Most applications do not call this method directly.
removeLayoutComponent
in interface LayoutManager
comp
- the component to be removed.
Container.remove(java.awt.Component)
, Container.removeAll()
public Component getLayoutComponent(Object constraints)
constraints
- the desired constraint, one of CENTER
, NORTH
, SOUTH
, WEST
, EAST
, PAGE_START
, PAGE_END
, LINE_START
, LINE_END
IllegalArgumentException
- if the constraint object is not one of the nine specified constants
addLayoutComponent(java.awt.Component, java.lang.Object)
public Component getLayoutComponent(Container target, Object constraints)
constraints
- the desired absolute position, one of CENTER
, one of NORTH
, SOUTH
, EAST
, WEST
target
- the Container
using this BorderLayout
IllegalArgumentException
- if the constraint object is not one of the five specified constants
NullPointerException
- if the target parameter is null
addLayoutComponent(java.awt.Component, java.lang.Object)
public Object getConstraints(Component comp)
comp
- the component to be queried
addLayoutComponent(java.awt.Component, java.lang.Object)
public Dimension minimumLayoutSize(Container target)
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.
minimumLayoutSize
in interface LayoutManager
target
- the container in which to do the layout.
Container
, preferredLayoutSize(java.awt.Container)
, Container.getMinimumSize()
public Dimension preferredLayoutSize(Container target)
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.
preferredLayoutSize
in interface LayoutManager
target
- the container in which to do the layout.
Container
, minimumLayoutSize(java.awt.Container)
, Container.getPreferredSize()
public Dimension maximumLayoutSize(Container target)
maximumLayoutSize
in interface LayoutManager2
target
- the component which needs to be laid out
Container
, minimumLayoutSize(java.awt.Container)
, preferredLayoutSize(java.awt.Container)
public float getLayoutAlignmentX(Container parent)
getLayoutAlignmentX
in interface LayoutManager2
public float getLayoutAlignmentY(Container parent)
getLayoutAlignmentY
in interface LayoutManager2
public void invalidateLayout(Container target)
invalidateLayout
in interface LayoutManager2
public void layoutContainer(Container target)
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.
layoutContainer
in interface LayoutManager
target
- the container in which to do the layout.
Container
, Container.doLayout()
public String toString()
toString
in class Object
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