BorderLayout JDK 1.6)

Description

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.

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:

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);
   }
 }

See also: Container.add(String, Component) ComponentOrientation

Methods

Hide/Show inherited methods

public void addLayoutComponent (Component comp, Object constraints) [Specified in LayoutManager2]

Adds the specified component to the layout, using the specified constraint object.

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.
Throws:
- IllegalArgumentException - if the constraint object is not a string, or if it not one of the five specified constants.
Since: JDK1.1
See Also: Container.add(java.awt.Component, java.lang.Object),

@Deprecated

public void ~~addLayoutComponent~~ (String name, Component comp)

public Object getConstraints (Component comp)

Gets the constraints for the specified component

public int getHgap ()

Returns the horizontal gap between components.

public float getLayoutAlignmentX (Container parent) [Specified in LayoutManager2]

Returns the alignment along the x axis.

public float getLayoutAlignmentY (Container parent) [Specified in LayoutManager2]

Returns the alignment along the y axis.

public Component getLayoutComponent (Container target, Object constraints)

Returns the component that corresponds to the given constraint location based on the target Container's component orientation.

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.
Returns: the component at the given location, or null if the location is empty
Parameters:
- constraints - the desired absolute position, one of CENTER, NORTH, SOUTH, EAST, WEST
- target - the {@code Container} used to obtain the constraint location based on the target {@code Container}'s component orientation.
Throws:
- IllegalArgumentException - if the constraint object is not one of the five specified constants
- NullPointerException - if the target parameter is null
Since: 1.5
See Also: BorderLayout.addLayoutComponent(java.awt.Component, java.lang.Object),

public Component getLayoutComponent (Object constraints)

Gets the component that was added using the given constraint

Gets the component that was added using the given constraint
Returns: the component at the given location, or null if the location is empty
Parameters:
- constraints - the desired constraint, one of CENTER, NORTH, SOUTH, WEST, EAST, PAGE_START, PAGE_END, LINE_START, LINE_END
Throws:
- IllegalArgumentException - if the constraint object is not one of the nine specified constants
Since: 1.5
See Also: BorderLayout.addLayoutComponent(java.awt.Component, java.lang.Object),

public int getVgap ()

Returns the vertical gap between components.

public void invalidateLayout (Container target) [Specified in LayoutManager2]

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

public void layoutContainer (Container target)

Lays out the container argument using this border layout.

public Dimension maximumLayoutSize (Container target) [Specified in LayoutManager2]

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

public Dimension minimumLayoutSize (Container target)

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.
Returns: the minimum dimensions needed to lay out the subcomponents of the specified container.
Parameters:
- target - the container in which to do the layout.
See Also: Container, BorderLayout.preferredLayoutSize(java.awt.Container), Container.getMinimumSize(),

public Dimension preferredLayoutSize (Container target)

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.
Returns: the preferred dimensions to lay out the subcomponents of the specified container.
Parameters:
- target - the container in which to do the layout.
See Also: Container, BorderLayout.minimumLayoutSize(java.awt.Container), Container.getPreferredSize(),

public void removeLayoutComponent (Component comp)

Removes the specified component from this border 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.
Parameters:
- comp - the component to be removed.
See Also: Container.remove(java.awt.Component), Container.removeAll(),

public void setHgap (int hgap)

Sets the horizontal gap between components.

public void setVgap (int vgap)

Sets the vertical gap between components.

public String toString ()

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

Fields

Hide/Show inherited fields

publicfinalstatic String AFTER_LAST_LINE = "Last"

Synonym for PAGE_END.

publicfinalstatic String AFTER_LINE_ENDS = "After"

Synonym for LINE_END.

publicfinalstatic String BEFORE_FIRST_LINE = "First"

Synonym for PAGE_START.

publicfinalstatic String BEFORE_LINE_BEGINS = "Before"

Synonym for LINE_START.

pack-private Component center

Constant to specify components location to be the center portion of the border layout.

publicfinalstatic String CENTER = "Center"

The center layout constraint (middle of container).

pack-private Component east

Constant to specify components location to be the east portion of the border layout.

publicfinalstatic String EAST = "East"

The east layout constraint (right side of container).

pack-private Component firstItem

A relative positioning constant, that can be used instead of north, south, east, west or center.

pack-private Component firstLine

A relative positioning constant, that can be used instead of north, south, east, west or center.

A relative positioning constant, that can be used instead of
north, south, east, west or center.
mixing the two types of 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 BEFORE_FIRST_LINE constants in a container whose
orientation is LEFT_TO_RIGHT, only the
BEFORE_FIRST_LINE will be layed out.
This will be the same for lastLine, firstItem, lastItem.
Serial:

pack-private int hgap

Constructs a border layout with the horizontal gaps between components.

Constructs a border layout with the horizontal gaps
between components.
The horizontal gap is specified by hgap.
Serial:
See Also: BorderLayout.getHgap(), BorderLayout.setHgap(int),

pack-private Component lastItem

A relative positioning constant, that can be used instead of north, south, east, west or center.

pack-private Component lastLine

A relative positioning constant, that can be used instead of north, south, east, west or center.

publicfinalstatic String LINE_END = "After"

The component goes at the end of the line direction for the layout.

publicfinalstatic String LINE_START = "Before"

The component goes at the beginning of the line direction for the layout.

pack-private Component north

Constant to specify components location to be the north portion of the border layout.

publicfinalstatic String NORTH = "North"

The north layout constraint (top of container).

publicfinalstatic String PAGE_END = "Last"

The component comes after the last line of the layout's content.

publicfinalstatic String PAGE_START = "First"

The component comes before the first line of the layout's content.

pack-private Component south

Constant to specify components location to be the south portion of the border layout.

publicfinalstatic String SOUTH = "South"

The south layout constraint (bottom of container).

pack-private int vgap

Constructs a border layout with the vertical gaps between components.

Constructs a border layout with the vertical gaps
between components.
The vertical gap is specified by vgap.
Serial:
See Also: BorderLayout.getVgap(), BorderLayout.setVgap(int),

pack-private Component west

Constant to specify components location to be the west portion of the border layout.

publicfinalstatic String WEST = "West"

The west layout constraint (left side of container).