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); } }
Field Summary | |
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static String |
AFTER_LAST_LINE
Synonym for PAGE_END. |
static String |
AFTER_LINE_ENDS
Synonym for LINE_END. |
static String |
BEFORE_FIRST_LINE
Synonym for PAGE_START. |
static String |
BEFORE_LINE_BEGINS
Synonym for LINE_START. |
static String |
CENTER
The center layout constraint (middle of container). |
static String |
EAST
The east layout constraint (right side of container). |
static String |
LINE_END
The component goes at the end of the line direction for the layout. |
static String |
LINE_START
The component goes at the beginning of the line direction for the layout. |
static String |
NORTH
The north layout constraint (top of container). |
static String |
PAGE_END
The component comes after the last line of the layout's content. |
static String |
PAGE_START
The component comes before the first line of the layout's content. |
static String |
SOUTH
The south layout constraint (bottom of container). |
static String |
WEST
The west layout constraint (left side of container). |
Constructor Summary | |
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BorderLayout
() Constructs a new border layout with no gaps between components. |
|
BorderLayout
(int hgap, int vgap) Constructs a border layout with the specified gaps between components. |
Method Summary | |
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void |
addLayoutComponent
(
Component
comp,
Object
constraints) Adds the specified component to the layout, using the specified constraint object. |
void |
addLayoutComponent
(
String
name,
Component
comp) Deprecated. replaced by addLayoutComponent(Component, Object). |
Object |
getConstraints
(
Component
comp) Gets the constraints for the specified component |
int |
getHgap
() Returns the horizontal gap between components. |
float |
getLayoutAlignmentX
(
Container
parent) Returns the alignment along the x axis. |
float |
getLayoutAlignmentY
(
Container
parent) Returns the alignment along the y axis. |
Component |
getLayoutComponent
(
Container
target,
Object
Returns |
Component |
getLayoutComponent
(
Object
constraints) Gets the component that was added using the given constraint |
int |
getVgap
() Returns the vertical gap between components. |
void |
invalidateLayout
(
Container
target) Invalidates the layout, indicating that if the layout manager has cached information it should be discarded. |
void |
layoutContainer
(
Container
target) Lays out the container argument using this border layout. |
Dimension |
maximumLayoutSize
(
Container
target) Returns the maximum dimensions for this layout given the components in the specified target container. |
Dimension |
minimumLayoutSize
(
Container
target) Determines the minimum size of the target container using this layout manager. |
Dimension |
preferredLayoutSize
(
Container
target) Determines the preferred size of the target container using this layout manager, based on the components in the container. |
void |
removeLayoutComponent
(
Component
comp) Removes the specified component from this border layout. |
void |
setHgap
(int hgap) Sets the horizontal gap between components. |
void |
setVgap
(int vgap) Sets the vertical gap between components. |
String |
toString
() Returns a string representation of the state of this border layout. |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , wait , wait , wait |
Field Detail |
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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
public static final String AFTER_LAST_LINE
public static final String BEFORE_LINE_BEGINS
public static final String AFTER_LINE_ENDS
public static final String PAGE_START
public static final String PAGE_END
public static final String LINE_START
public static final String LINE_END
Constructor Detail |
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public BorderLayout()
public BorderLayout(int hgap, int vgap)
Method Detail |
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public int getHgap()
public void setHgap(int hgap)
public int getVgap()
public void setVgap(int vgap)
public void addLayoutComponent(Component comp, Object constraints)
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.
@Deprecated public void addLayoutComponent(String name, Component comp)
public void removeLayoutComponent(Component comp)
public Component getLayoutComponent(Object constraints)
public Component getLayoutComponent(Container target, Object constraints)
public Object getConstraints(Component comp)
public Dimension minimumLayoutSize(Container target)
This method is called when a container calls its getMinimumSize method. Most applications do not call this method directly.
public Dimension preferredLayoutSize(Container target)
Most applications do not call this method directly. This method is called when a container calls its getPreferredSize method.
public Dimension maximumLayoutSize(Container target)
public float getLayoutAlignmentX(Container parent)
public float getLayoutAlignmentY(Container parent)
public void invalidateLayout(Container target)
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.
public String toString()