public class BorderLayout extends Object implements LayoutManager2, Serializable
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 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 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 Formpublic static final String NORTH
The north layout constraint (top of container).
public static final String SOUTH
The south layout constraint (bottom of container).
public static final String EAST
The east layout constraint (right side of container).
public static final String WEST
The west layout constraint (left side of container).
public static final String CENTER
The center layout constraint (middle of container).
public static final String BEFORE_FIRST_LINE
Synonym for PAGE_START. Exists for compatibility with previous versions. PAGE_START is preferred.
PAGE_START, Constant Field Valuespublic static final String AFTER_LAST_LINE
Synonym for PAGE_END. Exists for compatibility with previous versions. PAGE_END is preferred.
PAGE_END, Constant Field Valuespublic static final String BEFORE_LINE_BEGINS
Synonym for LINE_START. Exists for compatibility with previous versions. LINE_START is preferred.
LINE_START, Constant Field Valuespublic static final String AFTER_LINE_ENDS
Synonym for LINE_END. Exists for compatibility with previous versions. LINE_END is preferred.
LINE_END, Constant Field Valuespublic static final String PAGE_START
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.
Component.getComponentOrientation(), Constant Field Valuespublic static final String PAGE_END
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.
Component.getComponentOrientation(), Constant Field Valuespublic static final String LINE_START
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.
Component.getComponentOrientation(), Constant Field Valuespublic static final String LINE_END
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.
Component.getComponentOrientation(), Constant Field Valuespublic BorderLayout()
Constructs a new border layout with no gaps between components.
public BorderLayout(int hgap,
int vgap) 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.public int getHgap()
Returns the horizontal gap between components.
public void setHgap(int hgap)
Sets the horizontal gap between components.
hgap - the horizontal gap between componentspublic int getVgap()
Returns the vertical gap between components.
public void setVgap(int vgap)
Sets the vertical gap between components.
vgap - the vertical gap between componentspublic void addLayoutComponent(Component comp,
Object constraints) 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.
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) Deprecated. replaced by addLayoutComponent(Component, Object).
Description copied from interface: LayoutManager
If the layout manager uses a per-component string, adds the component comp to the layout, associating it with the string specified by name.
addLayoutComponent in interface LayoutManager
name - the string to be associated with the componentcomp - the component to be addedpublic void removeLayoutComponent(Component comp)
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.
removeLayoutComponent in interface LayoutManager
comp - the component to be removed.Container.remove(java.awt.Component), Container.removeAll()
public Component getLayoutComponent(Object constraints)
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 constantsaddLayoutComponent(java.awt.Component, java.lang.Object)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. 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.
constraints - the desired absolute position, one of CENTER, NORTH, SOUTH, EAST, WEST
target - the Container used to obtain the constraint location based on the target Container's component orientation.null if the location is emptyIllegalArgumentException - if the constraint object is not one of the five specified constantsNullPointerException - if the target parameter is nulladdLayoutComponent(java.awt.Component, java.lang.Object)public Object getConstraints(Component comp)
Gets the constraints for the specified component
comp - the component to be queriedaddLayoutComponent(java.awt.Component, java.lang.Object)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.
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)
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.
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)
Returns the maximum dimensions for this layout given the components in the specified target container.
maximumLayoutSize in interface LayoutManager2
target - the component which needs to be laid outContainer, minimumLayoutSize(java.awt.Container), preferredLayoutSize(java.awt.Container)
public float getLayoutAlignmentX(Container parent)
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.
getLayoutAlignmentX in interface LayoutManager2
public float getLayoutAlignmentY(Container parent)
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.
getLayoutAlignmentY in interface LayoutManager2
public void invalidateLayout(Container target)
Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
invalidateLayout in interface LayoutManager2
public void layoutContainer(Container target)
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.
layoutContainer in interface LayoutManager
target - the container in which to do the layout.Container, Container.doLayout()
public String toString()
Returns a string representation of the state of this border layout.
© 1993–2017, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.