Chapter 19
java.awt Reference

GridBagLayout

Name

GridBagLayout

[Graphic: Figure from the text]

Description

The GridBagLayout LayoutManager provides the means to layout components in a flexible grid-based display model.

Class Definition

public class java.awt.GridBagLayout
    extends java.lang.Object
    implements java.awt.LayoutManager2, java.io.Serializable {
  
  // Protected Constants
  protected static final MAXGRIDSIZE;
  protected static final MINSIZE;
  protected static final PREFERREDSIZE;
  
  // Variables
  public double columnWeights[];
  public int columnWidths[];
  public int rowHeights[];
  public double rowWeights[];
  
  // Protected Variables
  protected Hashtable comptable;
  protected GridBagConstraints defaultConstraints;
  protected GridBagLayoutInfo layoutInfo;
  
  // Constructors
  public GridBagLayout();
  
  // Instance Methods
  public void addLayoutComponent (Component comp, Object constraints); 
  public void addLayoutComponent (String name, Component component);
  public GridBagConstraints getConstraints (Component component);
  public abstract float getLayoutAlignmentX(Container target); 
  public abstract float getLayoutAlignmentY(Container target); 
  public int[][] getLayoutDimensions();
  public Point getLayoutOrigin();
  public double[][] getLayoutWeights();
  public abstract void invalidateLayout(Container target); 
  public void layoutContainer (Container target);
  public Point location (int x, int y);
  public abstract Dimension maximumLayoutSize(Container target); 
  public Dimension minimumLayoutSize (Container target);
  public Dimension preferredLayoutSize (Container target);
  public void removeLayoutComponent (Component component);
  public void setConstraints (Component component, 
      GridBagConstraints constraints);
  public String toString();
  
  // Protected Instance Methods
  protected void AdjustForGravity (GridBagConstraints constraints, 
      Rectangle r);
  protected void ArrangeGrid (Container target);
  protected GridBagLayoutInfo GetLayoutInfo (Container target, 
      int sizeFlag);
  protected Dimension GetMinSize (Container target, 
      GridBagLayoutInfo info);
  protected GridBagConstraints lookupConstraints (Component comp); 
}

Protected Constants

MAXGRIDSIZE

protected static final MAXGRIDSIZE

Maximum number of rows and columns within container managed by GridBagLayout.

Variables

columnWeights

public double[] columnWeights

The weightx values of the components in the row with the most elements.

columnWidths

public int[] columnWidths

The width values of the components in the row with the most elements.

rowHeights

public int[] rowHeights

The height values of the components in the column with the most elements.

rowWeights

public double[] rowWeights

The weighty values of the components in the column with the most elements.

Protected Variables

defaultConstraints

protected GridBagConstraints defaultConstraints

Constraints to use for Components that have none.

layoutInfo

protected GridBagLayoutInfo layoutInfo

Internal information about the GridBagLayout.

Constructors

GridBagLayout

public GridBagLayout()

Description: Constructs a GridBagLayout object.

Instance Methods

addLayoutComponent

public void addLayoutComponent (Component comp, Object constraints)

Parameters

comp

The component being added.

constraints

An object describing the constraints on this component.

Implements

LayoutManager2.addLayoutComponent()

Description

Adds the component comp to container subject to the given constraints. This is a more generalized version of addLayoutComponent(String, Component). It corresponds to java.awt.Container's add(Component, Object).

public void addLayoutComponent (String name, Component component)

Parameters

name

Name of component to add.

component

Actual component being added.

Implements

LayoutManager.addLayoutComponent()

Description

Does nothing.

getConstraints

public GridBagConstraints getConstraints (Component component)

Parameters

component: Component whose constraints are desired

Returns

GridBagConstraints for component requested.

getLayoutAlignmentX

public abstract float getLayoutAlignmentX (Container target)

Parameters

target: The container to inspect.

Returns

The value .5 for all containers.

Description

This method returns the preferred alignment of the given container target. A return value of 0 is left aligned, .5 is centered, and 1 is right aligned.

getLayoutAlignmentY

public abstract float getLayoutAlignmentY (Container target)

Parameters

target: The container to inspect.

Returns

The value .5 for all containers.

Description

This method returns the preferred alignment of the given container target. A return value of 0 is top aligned, .5 is centered, and 1 is bottom aligned.

getLayoutDimensions

public int[][] getLayoutDimensions()

Returns: Returns two single dimension arrays as a multi-dimensional array. Index 0 is an array of widths (columnWidths instance variable), while index 1 is an array of heights (rowHeights instance variable).

getLayoutOrigin

public Point getLayoutOrigin()

Returns: Returns the origin of the components within the Container whose LayoutManager is GridBagLayout.

getLayoutWeights

public double[][] getLayoutWeights()

Returns: Returns two single dimension arrays as a multi-dimensional array. Index 0 is an array of columns weights (columnWeights instance variable), while index 1 is an array of row weights (rowWeights instance variable).

invalidateLayout

public abstract void invalidateLayout (Container target)

Parameters

target: The container to invalidate.

Description

Does nothing.

layoutContainer

public void layoutContainer (Container target)

Parameters

target: The container that needs to be redrawn.

Implements

LayoutManager.layoutContainer()

Description

Draws components contained within target.

location

public Point location (int x, int y)

Parameters

x

The x coordinate of the grid position to find.

y

The y coordinate of the grid position to find.

Returns

Returns the grid element under the location provided at position (x, y) in pixels. Note that the returned Point uses the GridBagLayout's grid for its coordinate space.

Description