java::awt::BorderLayout Class Reference

Inheritance diagram for java::awt::BorderLayout:

Inheritance graph
java::lang::Objectjava::lang::Interfacejava::awt::LayoutManager2java::awt::LayoutManager
[legend]
Collaboration diagram for java::awt::BorderLayout:

Collaboration graph
java::lang::Objectjava::lang::Interfacejava::lang::Stringjava::lang::ObjectRefjava::awt::LayoutManager2java::awt::LayoutManagerjava::lang::Comparable
[legend]

List of all members.


Detailed Description

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:

BorderLayout-1.gif

The code for this applet is as follows:


<blockquote>
 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);
   }
 }
 
</blockquote>

Version:
1.53, 01/23/03
Author:
Arthur van Hoff
See also:
java.awt.Container::add(String, Component)

java.awt.ComponentOrientation

Since:
JDK1.0

Public Member Functions

 BorderLayout (jint hgap=0, jint vgap=0)
 Constructs a new border layout with no gaps between components.
virtual jint getHgap () const
 Returns the horizontal gap between components.
virtual void setHgap (jint hgap)
 Sets the horizontal gap between components.
virtual jint getVgap () const
 Returns the vertical gap between components.
virtual void setVgap (jint vgap)
 Sets the vertical gap between components.
virtual void addLayoutComponent (const Ref< Component > &comp, const ObjectRef &constraints)
 Adds the specified component to the layout, using the specified constraint object.
virtual void addLayoutComponent (const String &name, const Ref< Component > &comp)
 If the layout manager uses a per-component string, adds the component comp to the layout, associating it with the string specified by name.
virtual void removeLayoutComponent (const Ref< Component > &comp)
 Removes the specified component from this border layout.
virtual Dimension minimumLayoutSize (const Container &target) const
 Determines the minimum size of the target container using this layout manager.
virtual Dimension preferredLayoutSize (const Container &target) const
 Determines the preferred size of the target container using this layout manager, based on the components in the container.
virtual Dimension maximumLayoutSize (const Container &target) const
 Returns the maximum dimensions for this layout given the components in the specified target container.
virtual jfloat getLayoutAlignmentX (const Container &target)
 Returns the alignment along the x axis.
virtual jfloat getLayoutAlignmentY (const Container &target)
 Returns the alignment along the y axis.
virtual void invalidateLayout (const Container &target)
 Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
virtual void layoutContainer (const Container &target)
 Lays out the container argument using this border layout.
virtual String toString () const
 Returns a string representation of the state of this border layout.

Static Public Attributes

static const String NORTH
 The north layout constraint (top of container).
static const String SOUTH
 The south layout constraint (bottom of container).
static const String EAST
 The east layout constraint (right side of container).
static const String WEST
 The west layout constraint (left side of container).
static const String CENTER
 The center layout constraint (middle of container).
static const String BEFORE_FIRST_LINE
 Synonym for PAGE_START.
static const String AFTER_LAST_LINE
 Synonym for PAGE_END.
static const String BEFORE_LINE_BEGINS
 Synonym for LINE_START.
static const String AFTER_LINE_ENDS
 Synonym for LINE_END.
static const String PAGE_START
 The component comes before the first line of the layout's content.
static const String PAGE_END
 The component comes after the last line of the layout's content.
static const String LINE_START
 The component goes at the beginning of the line direction for the layout.
static const String LINE_END
 The component goes at the end of the line direction for the layout.

Protected Attributes

ObjectRef impl
 REGISTER_MEMBERS

Constructor & Destructor Documentation

java::awt::BorderLayout::BorderLayout ( jint  hgap = 0,
jint  vgap = 0 
)

Constructs a new border layout with no gaps between components.


Member Function Documentation

virtual jint java::awt::BorderLayout::getHgap (  )  const [virtual]

Returns the horizontal gap between components.

Since:
JDK1.1

virtual void java::awt::BorderLayout::setHgap ( jint  hgap  )  [virtual]

Sets the horizontal gap between components.

Parameters:
hgap the horizontal gap between components
Since:
JDK1.1

virtual jint java::awt::BorderLayout::getVgap (  )  const [virtual]

Returns the vertical gap between components.

Since:
JDK1.1

virtual void java::awt::BorderLayout::setVgap ( jint  vgap  )  [virtual]

Sets the vertical gap between components.

Parameters:
vgap the vertical gap between components
Since:
JDK1.1

virtual void java::awt::BorderLayout::addLayoutComponent ( const Ref< Component > &  comp,
const ObjectRef constraints 
) [virtual]

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.

Parameters:
comp the component to be added.
constraints an object that specifies how and where the component is added to the layout.
See also:
java.awt.Container::add(java.awt.Component, java.lang.Object)
Exceptions:
IllegalArgumentException if the constraint object is not a string, or if it not one of the five specified constants.
Since:
JDK1.1

Implements java::awt::LayoutManager2.

virtual void java::awt::BorderLayout::addLayoutComponent ( const String name,
const Ref< Component > &  comp 
) [virtual]

If the layout manager uses a per-component string, adds the component comp to the layout, associating it with the string specified by name.

Parameters:
name the string to be associated with the component
comp the component to be added

Implements java::awt::LayoutManager.

virtual void java::awt::BorderLayout::removeLayoutComponent ( const Ref< Component > &  comp  )  [virtual]

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.

Parameters:
comp the component to be removed.
See also:
java.awt.Container::remove(java.awt.Component)

java.awt.Container::removeAll()

Implements java::awt::LayoutManager.

virtual Dimension java::awt::BorderLayout::minimumLayoutSize ( const Container target  )  const [virtual]

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.

Parameters:
target the container in which to do the layout.
Returns:
the minimum dimensions needed to lay out the subcomponents of the specified container.
See also:
java.awt.Container

java.awt.BorderLayout::preferredLayoutSize

java.awt.Container::getMinimumSize()

Implements java::awt::LayoutManager.

virtual Dimension java::awt::BorderLayout::preferredLayoutSize ( const Container target  )  const [virtual]

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.

Parameters:
target the container in which to do the layout.
Returns:
the preferred dimensions to lay out the subcomponents of the specified container.
See also:
java.awt.Container

java.awt.BorderLayout::minimumLayoutSize

java.awt.Container::getPreferredSize()

Implements java::awt::LayoutManager.

virtual Dimension java::awt::BorderLayout::maximumLayoutSize ( const Container target  )  const [virtual]

Returns the maximum dimensions for this layout given the components in the specified target container.

Parameters:
target the component which needs to be laid out
See also:
Container

minimumLayoutSize

preferredLayoutSize

Implements java::awt::LayoutManager2.

virtual jfloat java::awt::BorderLayout::getLayoutAlignmentX ( const Container target  )  [virtual]

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.

Implements java::awt::LayoutManager2.

virtual jfloat java::awt::BorderLayout::getLayoutAlignmentY ( const Container target  )  [virtual]

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.

Implements java::awt::LayoutManager2.

virtual void java::awt::BorderLayout::invalidateLayout ( const Container target  )  [virtual]

Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.

Implements java::awt::LayoutManager2.

virtual void java::awt::BorderLayout::layoutContainer ( const Container target  )  [virtual]

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.

Parameters:
target the container in which to do the layout.
See also:
java.awt.Container

java.awt.Container::doLayout()

Implements java::awt::LayoutManager.

virtual String java::awt::BorderLayout::toString (  )  const [virtual]

Returns a string representation of the state of this border layout.

Returns:
a string representation of this border layout.

Reimplemented from java::lang::Object.


Member Data Documentation

const String java::awt::BorderLayout::NORTH [static]

The north layout constraint (top of container).

const String java::awt::BorderLayout::SOUTH [static]

The south layout constraint (bottom of container).

const String java::awt::BorderLayout::EAST [static]

The east layout constraint (right side of container).

const String java::awt::BorderLayout::WEST [static]

The west layout constraint (left side of container).

const String java::awt::BorderLayout::CENTER [static]

The center layout constraint (middle of container).

const String java::awt::BorderLayout::BEFORE_FIRST_LINE [static]

Synonym for PAGE_START.

Exists for compatibility with previous versions. PAGE_START is preferred.

See also:
PAGE_START
Since:
1.2

const String java::awt::BorderLayout::AFTER_LAST_LINE [static]

Synonym for PAGE_END.

Exists for compatibility with previous versions. PAGE_END is preferred.

See also:
PAGE_END
Since:
1.2

const String java::awt::BorderLayout::BEFORE_LINE_BEGINS [static]

Synonym for LINE_START.

Exists for compatibility with previous versions. LINE_START is preferred.

See also:
LINE_START
Since:
1.2

const String java::awt::BorderLayout::AFTER_LINE_ENDS [static]

Synonym for LINE_END.

Exists for compatibility with previous versions. LINE_END is preferred.

See also:
LINE_END
Since:
1.2

const String java::awt::BorderLayout::PAGE_START [static]

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.

See also:
java.awt.Component::getComponentOrientation
Since:
1.4

const String java::awt::BorderLayout::PAGE_END [static]

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.

See also:
java.awt.Component::getComponentOrientation
Since:
1.4

const String java::awt::BorderLayout::LINE_START [static]

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.

See also:
java.awt.Component::getComponentOrientation
Since:
1.4

const String java::awt::BorderLayout::LINE_END [static]

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.

See also:
java.awt.Component::getComponentOrientation
Since:
1.4

ObjectRef java::awt::BorderLayout::impl [protected]

java::awt::BorderLayout::REGISTER_MEMBERS [protected]

Reimplemented from java::awt::LayoutManager2.


The documentation for this class was generated from the following file:
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