GridBagLayout

Name

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.

MINSIZE

protected static final MINSIZE

Used for internal sizing purposes.

PREFERREDSIZE

protected static final PREFERREDSIZE

Used for internal sizing purposes.

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

comptable

protected Hashtable comptable

Internal table to manage components.

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
• Locates the grid position in the Container under the given location.

maximumLayoutSize

public abstract Dimension maximumLayoutSize (Container target)

• Parameters
• • target
  • The container to inspect.
• Returns
• A Dimension whose horizontal and vertical components are Integer.MAX_VALUE.
• Description
• For GridBagLayout, a maximal Dimension is always returned.

minimumLayoutSize

public Dimension minimumLayoutSize (Container target)

• Parameters
• • target
  • The container whose size needs to be calculated.
• Returns
• Minimum Dimension of container target.
• Implements
• LayoutManager.minimumLayoutSize()
• Description
• Calculates minimum size of target container.

preferredLayoutSize

public Dimension preferredLayoutSize (Container target)

• Parameters
• • target
  • The container whose size needs to be calculated.
• Returns
• Preferred Dimension of container target
• Implements
• LayoutManager.preferredLayoutSize()
• Description
• Calculates preferred size of target container.

removeLayoutComponent

public void removeLayoutComponent (Component component)

• Parameters
• • component
  • Component to stop tracking.
• Implements
• LayoutManager.removeLayoutComponent()
• Description
• Does nothing.

setConstraints

public void setConstraints (Component component, GridBagConstraints constraints)

• Parameters
• • component
  • Component to set constraints for
  • constraints
  • Constraints for component
• Description
• Changes the GridBagConstraints on component to those provided.

toString

public String toString()

• Returns
• A string representation of the GridBagLayout object.
• Overrides
• Object.toString()

Protected Instance Methods

AdjustForGravity

protected void AdjustForGravity (GridBagConstraints constraints, Rectangle r)

• Parameters
• • constraints
  • Constraints to use for adjustment of Rectangle.
  • r
  • Rectangular area that needs to be adjusted.
• Description
• Helper routine for laying out a cell of the grid. The routine adjusts the values for r based upon the constraints.

ArrangeGrid

protected void ArrangeGrid (Container target)

• Parameters
• • target
  • Container to layout.
• Description
• Helper routine that does the actual arrangement of components in target.

GetLayoutInfo

protected GridBagLayoutInfo GetLayoutInfo (Container target, int sizeFlag)

• Parameters
• • target
  • Container to get information about.
  • sizeFlag
  • One of the constants MINSIZE or PREFERREDSIZE.
• Returns
• Returns an internal class used to help size the container.

GetMinSize

protected Dimension GetMinSize (Container target, GridBagLayoutInfo info)

• Parameters
• • target
  • Container to calculate size.
  • info
  • Specifics about the container's constraints.
• Returns
• Minimum Dimension of container target based on info.
• Description
• Helper routine for calculating size of container.

lookupConstraints

protected GridBagConstraints lookupConstraints (Component comp)

• Parameters
• • comp
  • Component in question.
• Returns
• A reference to the GridBagConstraints object for this component.
• Description
• Helper routine for calculating size of container.

See Also

Component, Container, Dimension, GridBagConstraints, Hashtable, LayoutManager, LayoutManager2, Object, Point, Rectangle, String