- java.lang.Object
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- java.awt.BorderLayout
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- All Implemented Interfaces:
LayoutManager,LayoutManager2,Serializable
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, andCENTER. 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,BorderLayoutinterprets the absence of a string specification the same as the constantCENTER:Panel p2 = new Panel(); p2.setLayout(new BorderLayout()); p2.add(new TextArea()); // Same as p.add(new TextArea(), BorderLayout.CENTER);In addition,
BorderLayoutsupports the relative positioning constants,PAGE_START,PAGE_END,LINE_START, andLINE_END. In a container whoseComponentOrientationis set toComponentOrientation.LEFT_TO_RIGHT, these constants map toNORTH,SOUTH,WEST, andEAST, respectively.For compatibility with previous releases,
BorderLayoutalso includes the relative positioning constantsBEFORE_FIRST_LINE,AFTER_LAST_LINE,BEFORE_LINE_BEGINSandAFTER_LINE_ENDS. These are equivalent toPAGE_START,PAGE_END,LINE_STARTandLINE_ENDrespectively. 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
NORTHandPAGE_STARTconstants in a container whose orientation isLEFT_TO_RIGHT, only thePAGE_STARTwill be laid out.NOTE: Currently,
BorderLayoutdoes not support vertical orientations. TheisVerticalsetting on the container'sComponentOrientationis not respected.The components are laid out according to their preferred sizes and the constraints of the container's size. The
NORTHandSOUTHcomponents may be stretched horizontally; theEASTandWESTcomponents may be stretched vertically; theCENTERcomponent 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
BorderLayoutlayout 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); } }- Since:
- 1.0
- See Also:
Container.add(String, Component),ComponentOrientation, Serialized Form
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Field Summary
Fields Modifier and Type Field Description static StringAFTER_LAST_LINESynonym for PAGE_END.static StringAFTER_LINE_ENDSSynonym for LINE_END.static StringBEFORE_FIRST_LINESynonym for PAGE_START.static StringBEFORE_LINE_BEGINSSynonym for LINE_START.static StringCENTERThe center layout constraint (middle of container).static StringEASTThe east layout constraint (right side of container).static StringLINE_ENDThe component goes at the end of the line direction for the layout.static StringLINE_STARTThe component goes at the beginning of the line direction for the layout.static StringNORTHThe north layout constraint (top of container).static StringPAGE_ENDThe component comes after the last line of the layout's content.static StringPAGE_STARTThe component comes before the first line of the layout's content.static StringSOUTHThe south layout constraint (bottom of container).static StringWESTThe west layout constraint (left side of container).
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Constructor Summary
Constructors Constructor Description 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.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description voidaddLayoutComponent(Component comp, Object constraints)Adds the specified component to the layout, using the specified constraint object.voidaddLayoutComponent(String name, Component comp)Deprecated.replaced byaddLayoutComponent(Component, Object).ObjectgetConstraints(Component comp)Gets the constraints for the specified componentintgetHgap()Returns the horizontal gap between components.floatgetLayoutAlignmentX(Container parent)Returns the alignment along the x axis.floatgetLayoutAlignmentY(Container parent)Returns the alignment along the y axis.ComponentgetLayoutComponent(Container target, Object constraints)Returns the component that corresponds to the given constraint location based on the targetContainer's component orientation.ComponentgetLayoutComponent(Object constraints)Gets the component that was added using the given constraintintgetVgap()Returns the vertical gap between components.voidinvalidateLayout(Container target)Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.voidlayoutContainer(Container target)Lays out the container argument using this border layout.DimensionmaximumLayoutSize(Container target)Returns the maximum dimensions for this layout given the components in the specified target container.DimensionminimumLayoutSize(Container target)Determines the minimum size of thetargetcontainer using this layout manager.DimensionpreferredLayoutSize(Container target)Determines the preferred size of thetargetcontainer using this layout manager, based on the components in the container.voidremoveLayoutComponent(Component comp)Removes the specified component from this border layout.voidsetHgap(int hgap)Sets the horizontal gap between components.voidsetVgap(int vgap)Sets the vertical gap between components.StringtoString()Returns a string representation of the state of this border layout.
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Field Detail
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NORTH
public static final String NORTH
The north layout constraint (top of container).- See Also:
- Constant Field Values
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SOUTH
public static final String SOUTH
The south layout constraint (bottom of container).- See Also:
- Constant Field Values
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EAST
public static final String EAST
The east layout constraint (right side of container).- See Also:
- Constant Field Values
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WEST
public static final String WEST
The west layout constraint (left side of container).- See Also:
- Constant Field Values
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CENTER
public static final String CENTER
The center layout constraint (middle of container).- See Also:
- Constant Field Values
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BEFORE_FIRST_LINE
public static final String BEFORE_FIRST_LINE
Synonym for PAGE_START. Exists for compatibility with previous versions. PAGE_START is preferred.- Since:
- 1.2
- See Also:
PAGE_START, Constant Field Values
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AFTER_LAST_LINE
public static final String AFTER_LAST_LINE
Synonym for PAGE_END. Exists for compatibility with previous versions. PAGE_END is preferred.- Since:
- 1.2
- See Also:
PAGE_END, Constant Field Values
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BEFORE_LINE_BEGINS
public static final String BEFORE_LINE_BEGINS
Synonym for LINE_START. Exists for compatibility with previous versions. LINE_START is preferred.- Since:
- 1.2
- See Also:
LINE_START, Constant Field Values
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AFTER_LINE_ENDS
public static final String AFTER_LINE_ENDS
Synonym for LINE_END. Exists for compatibility with previous versions. LINE_END is preferred.- Since:
- 1.2
- See Also:
LINE_END, Constant Field Values
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PAGE_START
public 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.- Since:
- 1.4
- See Also:
Component.getComponentOrientation(), Constant Field Values
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PAGE_END
public 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.- Since:
- 1.4
- See Also:
Component.getComponentOrientation(), Constant Field Values
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LINE_START
public 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.- Since:
- 1.4
- See Also:
Component.getComponentOrientation(), Constant Field Values
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LINE_END
public 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.- Since:
- 1.4
- See Also:
Component.getComponentOrientation(), Constant Field Values
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Constructor Detail
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BorderLayout
public BorderLayout()
Constructs a new border layout with no gaps between components.
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BorderLayout
public BorderLayout(int hgap, int vgap)Constructs a border layout with the specified gaps between components. The horizontal gap is specified byhgapand the vertical gap is specified byvgap.- Parameters:
hgap- the horizontal gap.vgap- the vertical gap.
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Method Detail
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getHgap
public int getHgap()
Returns the horizontal gap between components.- Returns:
- the horizontal gap between components
- Since:
- 1.1
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setHgap
public void setHgap(int hgap)
Sets the horizontal gap between components.- Parameters:
hgap- the horizontal gap between components- Since:
- 1.1
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getVgap
public int getVgap()
Returns the vertical gap between components.- Returns:
- the vertical gap between components
- Since:
- 1.1
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setVgap
public void setVgap(int vgap)
Sets the vertical gap between components.- Parameters:
vgap- the vertical gap between components- Since:
- 1.1
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addLayoutComponent
public 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, orCENTER.Most applications do not call this method directly. This method is called when a component is added to a container using the
Container.addmethod with the same argument types.- Specified by:
addLayoutComponentin interfaceLayoutManager2- 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:
- 1.1
- See Also:
Container.add(java.awt.Component, java.lang.Object)
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addLayoutComponent
@Deprecated public void addLayoutComponent(String name, Component comp)
Deprecated.replaced byaddLayoutComponent(Component, Object).Description copied from interface:LayoutManagerIf the layout manager uses a per-component string, adds the componentcompto the layout, associating it with the string specified byname.- Specified by:
addLayoutComponentin interfaceLayoutManager- Parameters:
name- the string to be associated with the componentcomp- the component to be added
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removeLayoutComponent
public void removeLayoutComponent(Component comp)
Removes the specified component from this border layout. This method is called when a container calls itsremoveorremoveAllmethods. Most applications do not call this method directly.- Specified by:
removeLayoutComponentin interfaceLayoutManager- Parameters:
comp- the component to be removed.- See Also:
Container.remove(java.awt.Component),Container.removeAll()
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getLayoutComponent
public Component getLayoutComponent(Object constraints)
Gets the component that was added using the given constraint- Parameters:
constraints- the desired constraint, one ofCENTER,NORTH,SOUTH,WEST,EAST,PAGE_START,PAGE_END,LINE_START,LINE_END- Returns:
- the component at the given location, or
nullif the location is empty - Throws:
IllegalArgumentException- if the constraint object is not one of the nine specified constants- Since:
- 1.5
- See Also:
addLayoutComponent(java.awt.Component, java.lang.Object)
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getLayoutComponent
public Component getLayoutComponent(Container target, Object constraints)
Returns the component that corresponds to the given constraint location based on the targetContainer's component orientation. Components added with the relative constraintsPAGE_START,PAGE_END,LINE_START, andLINE_ENDtake precedence over components added with the explicit constraintsNORTH,SOUTH,WEST, andEAST. TheContainer's component orientation is used to determine the location of components added withLINE_STARTandLINE_END.- Parameters:
constraints- the desired absolute position, one ofCENTER,NORTH,SOUTH,EAST,WESTtarget- theContainerused to obtain the constraint location based on the targetContainer's component orientation.- Returns:
- the component at the given location, or
nullif the location is empty - Throws:
IllegalArgumentException- if the constraint object is not one of the five specified constantsNullPointerException- if the target parameter is null- Since:
- 1.5
- See Also:
addLayoutComponent(java.awt.Component, java.lang.Object)
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getConstraints
public Object getConstraints(Component comp)
Gets the constraints for the specified component- Parameters:
comp- the component to be queried- Returns:
- the constraint for the specified component, or null if component is null or is not present in this layout
- Since:
- 1.5
- See Also:
addLayoutComponent(java.awt.Component, java.lang.Object)
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minimumLayoutSize
public Dimension minimumLayoutSize(Container target)
Determines the minimum size of thetargetcontainer using this layout manager.This method is called when a container calls its
getMinimumSizemethod. Most applications do not call this method directly.- Specified by:
minimumLayoutSizein interfaceLayoutManager- 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:
Container,preferredLayoutSize(java.awt.Container),Container.getMinimumSize()
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preferredLayoutSize
public Dimension preferredLayoutSize(Container target)
Determines the preferred size of thetargetcontainer 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
getPreferredSizemethod.- Specified by:
preferredLayoutSizein interfaceLayoutManager- 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:
Container,minimumLayoutSize(java.awt.Container),Container.getPreferredSize()
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maximumLayoutSize
public Dimension maximumLayoutSize(Container target)
Returns the maximum dimensions for this layout given the components in the specified target container.- Specified by:
maximumLayoutSizein interfaceLayoutManager2- Parameters:
target- the component which needs to be laid out- Returns:
- the maximum size of the container
- See Also:
Container,minimumLayoutSize(java.awt.Container),preferredLayoutSize(java.awt.Container)
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getLayoutAlignmentX
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.- Specified by:
getLayoutAlignmentXin interfaceLayoutManager2- Parameters:
parent- the target container- Returns:
- the x-axis alignment preference
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getLayoutAlignmentY
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.- Specified by:
getLayoutAlignmentYin interfaceLayoutManager2- Parameters:
parent- the target container- Returns:
- the y-axis alignment preference
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invalidateLayout
public void invalidateLayout(Container target)
Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.- Specified by:
invalidateLayoutin interfaceLayoutManager2- Parameters:
target- the target container
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layoutContainer
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
BorderLayoutobject. TheNORTHandSOUTHcomponents, if any, are placed at the top and bottom of the container, respectively. TheWESTandEASTcomponents are then placed on the left and right, respectively. Finally, theCENTERobject 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
doLayoutmethod.- Specified by:
layoutContainerin interfaceLayoutManager- Parameters:
target- the container in which to do the layout.- See Also:
Container,Container.doLayout()
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