Class BorderLayout

java.lang.Object
java.awt.BorderLayout
All Implemented Interfaces:
LayoutManager,LayoutManager2,Serializable
public classBorderLayoutextendsObjectimplementsLayoutManager2,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,BorderLayout interprets 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,BorderLayout supports the relative positioning constants,PAGE_START,PAGE_END,LINE_START, andLINE_END. In a container whoseComponentOrientation is set toComponentOrientation.LEFT_TO_RIGHT, these constants map toNORTH,SOUTH,WEST, andEAST, respectively.

For compatibility with previous releases,BorderLayout also includes the relative positioning constantsBEFORE_FIRST_LINE,AFTER_LAST_LINE,BEFORE_LINE_BEGINS andAFTER_LINE_ENDS. These are equivalent toPAGE_START,PAGE_END,LINE_START andLINE_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 theNORTH andPAGE_START constants in a container whose orientation isLEFT_TO_RIGHT, only thePAGE_START will be laid out.

NOTE: Currently,BorderLayout does not support vertical orientations. TheisVertical setting on the container'sComponentOrientation is not respected.

The components are laid out according to their preferred sizes and the constraints of the container's size. TheNORTH andSOUTH components may be stretched horizontally; theEAST andWEST components may be stretched vertically; theCENTER 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 theBorderLayout 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);   } }

Since:
1.0
See Also:

  • Field Details

  • Constructor Details

    • BorderLayout

      public BorderLayout()
      Constructs a new border layout with no gaps between components.

    • BorderLayout

      public BorderLayout(int hgap, int vgap)
      Constructs a border layout with the specified gaps between components. The horizontal gap is specified byhgap and the vertical gap is specified byvgap.
      Parameters:
      hgap - the horizontal gap.
      vgap - the vertical gap.

  • Method Details

    • getHgap

      public int getHgap()
      Returns the horizontal gap between components.
      Returns:
      the horizontal gap between components
      Since:
      1.1

    • setHgap

      public void setHgap(int hgap)
      Sets the horizontal gap between components.
      Parameters:
      hgap - the horizontal gap between components
      Since:
      1.1

    • getVgap

      public int getVgap()
      Returns the vertical gap between components.
      Returns:
      the vertical gap between components
      Since:
      1.1

    • setVgap

      public void setVgap(int vgap)
      Sets the vertical gap between components.
      Parameters:
      vgap - the vertical gap between components
      Since:
      1.1

    • 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 theContainer.add method with the same argument types.

      Specified by:
      addLayoutComponent in interface LayoutManager2
      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:

    • addLayoutComponent

      @Deprecatedpublic void addLayoutComponent(String name,Component comp)
      Deprecated.
      replaced byaddLayoutComponent(Component, Object).
      Description copied from interface: LayoutManager
      If the layout manager uses a per-component string, adds the componentcomp to the layout, associating it with the string specified byname.
      Specified by:
      addLayoutComponent in interface LayoutManager
      Parameters:
      name - the string to be associated with the component
      comp - the component to be added

    • removeLayoutComponent

      public void removeLayoutComponent(Component comp)
      Removes the specified component from this border layout. This method is called when a container calls itsremove orremoveAll methods. Most applications do not call this method directly.
      Specified by:
      removeLayoutComponent in interface LayoutManager
      Parameters:
      comp - the component to be removed.
      See Also:

    • 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, ornull if the location is empty
      Throws:
      IllegalArgumentException - if the constraint object is not one of the nine specified constants
      Since:
      1.5
      See Also:

    • 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_END take 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_START andLINE_END.
      Parameters:
      target - theContainer used to obtain the constraint location based on the targetContainer's component orientation.
      constraints - the desired absolute position, one ofCENTER,NORTH,SOUTH,EAST,WEST
      Returns:
      the component at the given location, ornull if the location is empty
      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:

    • 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:

    • minimumLayoutSize

      public Dimension minimumLayoutSize(Container target)
      Determines the minimum size of thetarget container using this layout manager.

      This method is called when a container calls itsgetMinimumSize method. Most applications do not call this method directly.

      Specified by:
      minimumLayoutSize in interface LayoutManager
      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:

    • preferredLayoutSize

      public Dimension preferredLayoutSize(Container target)
      Determines the preferred size of thetarget 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 itsgetPreferredSize method.

      Specified by:
      preferredLayoutSize in interface LayoutManager
      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:

    • maximumLayoutSize

      public Dimension maximumLayoutSize(Container target)
      Returns the maximum dimensions for this layout given the components in the specified target container.
      Specified by:
      maximumLayoutSize in interface LayoutManager2
      Parameters:
      target - the component which needs to be laid out
      Returns:
      the maximum size of the container
      See Also:

    • 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:
      getLayoutAlignmentX in interface LayoutManager2
      Parameters:
      parent - the target container
      Returns:
      the x-axis alignment preference

    • 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:
      getLayoutAlignmentY in interface LayoutManager2
      Parameters:
      parent - the target container
      Returns:
      the y-axis alignment preference

    • invalidateLayout

      public void invalidateLayout(Container target)
      Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
      Specified by:
      invalidateLayout in interface LayoutManager2
      Parameters:
      target - the target container

    • 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 thisBorderLayout object. TheNORTH andSOUTH components, if any, are placed at the top and bottom of the container, respectively. TheWEST andEAST components are then placed on the left and right, respectively. Finally, theCENTER 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 itsdoLayout method.

      Specified by:
      layoutContainer in interface LayoutManager
      Parameters:
      target - the container in which to do the layout.
      See Also:

    • toString

      public String toString()
      Returns a string representation of the state of this border layout.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this border layout.