public class GridBagLayout extends Object implements LayoutManager2, Serializable
GridBagLayout class is a flexible layout
 manager that aligns components vertically, horizontally or along their
 baseline without requiring that the components be of the same size.
 Each GridBagLayout object maintains a dynamic,
 rectangular grid of cells, with each component occupying
 one or more cells, called its display area.
 
 Each component managed by a GridBagLayout is associated with
 an instance of GridBagConstraints.  The constraints object
 specifies where a component's display area should be located on the grid
 and how the component should be positioned within its display area.  In
 addition to its constraints object, the GridBagLayout also
 considers each component's minimum and preferred sizes in order to
 determine a component's size.
 
 The overall orientation of the grid depends on the container's
 ComponentOrientation property.  For horizontal left-to-right
 orientations, grid coordinate (0,0) is in the upper left corner of the
 container with x increasing to the right and y increasing downward.  For
 horizontal right-to-left orientations, grid coordinate (0,0) is in the upper
 right corner of the container with x increasing to the left and y
 increasing downward.
 
 To use a grid bag layout effectively, you must customize one or more
 of the GridBagConstraints objects that are associated
 with its components. You customize a GridBagConstraints
 object by setting one or more of its instance variables:
 
GridBagConstraints.gridx,
 GridBagConstraints.gridy
 gridx = 0,
 gridy = 0.  For horizontal left-to-right layout,
 a component's leading corner is its upper left.  For horizontal
 right-to-left layout, a component's leading corner is its upper right.
 Use GridBagConstraints.RELATIVE (the default value)
 to specify that the component be placed immediately following
 (along the x axis for gridx or the y axis for
 gridy) the component that was added to the container
 just before this component was added.
 GridBagConstraints.gridwidth,
 GridBagConstraints.gridheight
 gridwidth)
 or column (for gridheight)
 in the component's display area.
 The default value is 1.
 Use GridBagConstraints.REMAINDER to specify
 that the component's display area will be from gridx
 to the last cell in the row (for gridwidth)
 or from gridy to the last cell in the column
 (for gridheight).
 Use GridBagConstraints.RELATIVE to specify
 that the component's display area will be from gridx
 to the next to the last cell in its row (for gridwidth
 or from gridy to the next to the last cell in its
 column (for gridheight).
 GridBagConstraints.fill
 GridBagConstraints.NONE (the default),
 GridBagConstraints.HORIZONTAL
 (make the component wide enough to fill its display area
 horizontally, but don't change its height),
 GridBagConstraints.VERTICAL
 (make the component tall enough to fill its display area
 vertically, but don't change its width), and
 GridBagConstraints.BOTH
 (make the component fill its display area entirely).
 GridBagConstraints.ipadx,
 GridBagConstraints.ipady
 ipadx pixels. Similarly, the height of
 the component will be at least the minimum height plus
 ipady pixels.
 GridBagConstraints.insets
 GridBagConstraints.anchor
 ComponentOrientation property while absolute values
 are not.  Baseline relative values are calculated relative to the
 baseline.  Valid values are:
 | Absolute Values | Orientation Relative Values | Baseline Relative Values | 
|---|---|---|
| 
 | 
 | 
 | 
GridBagConstraints.weightx,
 GridBagConstraints.weighty
 weightx) and column (weighty),
 all the components clump together in the center of their container.
 This is because when the weight is zero (the default),
 the GridBagLayout object puts any extra space
 between its grid of cells and the edges of the container.
 
 Each row may have a baseline; the baseline is determined by the
 components in that row that have a valid baseline and are aligned
 along the baseline (the component's anchor value is one of BASELINE, BASELINE_LEADING or BASELINE_TRAILING).
 If none of the components in the row has a valid baseline, the row
 does not have a baseline.
 
 If a component spans rows it is aligned either to the baseline of
 the start row (if the baseline-resize behavior is CONSTANT_ASCENT) or the end row (if the baseline-resize behavior
 is CONSTANT_DESCENT).  The row that the component is
 aligned to is called the prevailing row.
 
The following figure shows a baseline layout and includes a component that spans rows:
|   | 
CONSTANT_DESCENT and has
   an anchor of BASELINE.  As the baseline-resize behavior
   is CONSTANT_DESCENT the prevailing row for the panel is
   row 1.
 CENTER_OFFSET and an anchor of BASELINE.
 
 Components positioned using one of the baseline-relative values resize
 differently than when positioned using an absolute or orientation-relative
 value.  How components change is dictated by how the baseline of the
 prevailing row changes.  The baseline is anchored to the
 bottom of the display area if any components with the same prevailing row
 have a baseline-resize behavior of CONSTANT_DESCENT,
 otherwise the baseline is anchored to the top of the display area.
 The following rules dictate the resize behavior:
 
OTHER are only resized if
 the baseline at the resized size fits within the display area.  If
 the baseline is such that it does not fit within the display area
 the component is not resized.
 OTHER
 can only grow as tall as display height - baseline + baseline of component.
 The following figures show ten components (all buttons) managed by a grid bag layout. Figure 2 shows the layout for a horizontal, left-to-right container and Figure 3 shows the layout for a horizontal, right-to-left container.
|   |   | 
| Figure 2: Horizontal, Left-to-Right | Figure 3: Horizontal, Right-to-Left | 
 Each of the ten components has the fill field
 of its associated GridBagConstraints object
 set to GridBagConstraints.BOTH.
 In addition, the components have the following non-default constraints:
 
weightx = 1.0
 weightx = 1.0,
 gridwidth = GridBagConstraints.REMAINDER
 gridwidth = GridBagConstraints.REMAINDER
 gridwidth = GridBagConstraints.RELATIVE
 gridwidth = GridBagConstraints.REMAINDER
 gridheight = 2,
 weighty = 1.0
 gridwidth = GridBagConstraints.REMAINDER
 Here is the code that implements the example shown above:
 import java.awt.*;
 import java.util.*;
 import java.applet.Applet;
 public class GridBagEx1 extends Applet {
     protected void makebutton(String name,
                               GridBagLayout gridbag,
                               GridBagConstraints c) {
         Button button = new Button(name);
         gridbag.setConstraints(button, c);
         add(button);
     }
     public void init() {
         GridBagLayout gridbag = new GridBagLayout();
         GridBagConstraints c = new GridBagConstraints();
         setFont(new Font("SansSerif", Font.PLAIN, 14));
         setLayout(gridbag);
         c.fill = GridBagConstraints.BOTH;
         c.weightx = 1.0;
         makebutton("Button1", gridbag, c);
         makebutton("Button2", gridbag, c);
         makebutton("Button3", gridbag, c);
         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         makebutton("Button4", gridbag, c);
         c.weightx = 0.0;                //reset to the default
         makebutton("Button5", gridbag, c); //another row
         c.gridwidth = GridBagConstraints.RELATIVE; //next-to-last in row
         makebutton("Button6", gridbag, c);
         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         makebutton("Button7", gridbag, c);
         c.gridwidth = 1;                //reset to the default
         c.gridheight = 2;
         c.weighty = 1.0;
         makebutton("Button8", gridbag, c);
         c.weighty = 0.0;                //reset to the default
         c.gridwidth = GridBagConstraints.REMAINDER; //end row
         c.gridheight = 1;               //reset to the default
         makebutton("Button9", gridbag, c);
         makebutton("Button10", gridbag, c);
         setSize(300, 100);
     }
     public static void main(String args[]) {
         Frame f = new Frame("GridBag Layout Example");
         GridBagEx1 ex1 = new GridBagEx1();
         ex1.init();
         f.add("Center", ex1);
         f.pack();
         f.setSize(f.getPreferredSize());
         f.show();
     }
 }
 GridBagConstraints, 
GridBagLayoutInfo, 
ComponentOrientation, 
Serialized Form| Modifier and Type | Field and Description | 
|---|---|
| double[] | columnWeightsThis field holds the overrides to the column weights. | 
| int[] | columnWidthsThis field holds the overrides to the column minimum
 width. | 
| protected Hashtable<Component,GridBagConstraints> | comptableThis hashtable maintains the association between
 a component and its gridbag constraints. | 
| protected GridBagConstraints | defaultConstraintsThis field holds a gridbag constraints instance
 containing the default values, so if a component
 does not have gridbag constraints associated with
 it, then the component will be assigned a
 copy of the  defaultConstraints. | 
| protected GridBagLayoutInfo | layoutInfoThis field holds the layout information
 for the gridbag. | 
| protected static int | MAXGRIDSIZEThis field is no longer used to reserve arrays and kept for backward
 compatibility. | 
| protected static int | MINSIZEThe smallest grid that can be laid out by the grid bag layout. | 
| protected static int | PREFERREDSIZEThe preferred grid size that can be laid out by the grid bag layout. | 
| int[] | rowHeightsThis field holds the overrides to the row minimum
 heights. | 
| double[] | rowWeightsThis field holds the overrides to the row weights. | 
| Constructor and Description | 
|---|
| GridBagLayout()Creates a grid bag layout manager. | 
| Modifier and Type | Method and Description | 
|---|---|
| void | addLayoutComponent(Component comp,
                  Object constraints)Adds the specified component to the layout, using the specified
  constraintsobject. | 
| void | addLayoutComponent(String name,
                  Component comp)Has no effect, since this layout manager does not use a per-component string. | 
| protected void | adjustForGravity(GridBagConstraints constraints,
                Rectangle r)Adjusts the x, y, width, and height fields to the correct
 values depending on the constraint geometry and pads. | 
| protected void | AdjustForGravity(GridBagConstraints constraints,
                Rectangle r)This method is obsolete and supplied for backwards
 compatibility only; new code should call  adjustForGravityinstead. | 
| protected void | arrangeGrid(Container parent)Lays out the grid. | 
| protected void | ArrangeGrid(Container parent)This method is obsolete and supplied for backwards
 compatibility only; new code should call  arrangeGridinstead. | 
| GridBagConstraints | getConstraints(Component comp)Gets the constraints for the specified component. | 
| float | getLayoutAlignmentX(Container parent)Returns the alignment along the x axis. | 
| float | getLayoutAlignmentY(Container parent)Returns the alignment along the y axis. | 
| int[][] | getLayoutDimensions()Determines column widths and row heights for the layout grid. | 
| protected GridBagLayoutInfo | getLayoutInfo(Container parent,
             int sizeflag)Fills in an instance of  GridBagLayoutInfofor the
 current set of managed children. | 
| protected GridBagLayoutInfo | GetLayoutInfo(Container parent,
             int sizeflag)This method is obsolete and supplied for backwards
 compatibility only; new code should call  getLayoutInfoinstead. | 
| Point | getLayoutOrigin()Determines the origin of the layout area, in the graphics coordinate
 space of the target container. | 
| double[][] | getLayoutWeights()Determines the weights of the layout grid's columns and rows. | 
| protected Dimension | getMinSize(Container parent,
          GridBagLayoutInfo info)Figures out the minimum size of the
 master based on the information from  getLayoutInfo. | 
| protected Dimension | GetMinSize(Container parent,
          GridBagLayoutInfo info)This method is obsolete and supplied for backwards
 compatibility only; new code should call  getMinSizeinstead. | 
| void | invalidateLayout(Container target)Invalidates the layout, indicating that if the layout manager
 has cached information it should be discarded. | 
| void | layoutContainer(Container parent)Lays out the specified container using this grid bag layout. | 
| Point | location(int x,
        int y)Determines which cell in the layout grid contains the point
 specified by  (x, y). | 
| protected GridBagConstraints | lookupConstraints(Component comp)Retrieves the constraints for the specified component. | 
| Dimension | maximumLayoutSize(Container target)Returns the maximum dimensions for this layout given the components
 in the specified target container. | 
| Dimension | minimumLayoutSize(Container parent)Determines the minimum size of the  parentcontainer
 using this grid bag layout. | 
| Dimension | preferredLayoutSize(Container parent)Determines the preferred size of the  parentcontainer using this grid bag layout. | 
| void | removeLayoutComponent(Component comp)Removes the specified component from this layout. | 
| void | setConstraints(Component comp,
              GridBagConstraints constraints)Sets the constraints for the specified component in this layout. | 
| String | toString()Returns a string representation of this grid bag layout's values. | 
protected static final int MAXGRIDSIZE
protected static final int MINSIZE
protected static final int PREFERREDSIZE
protected Hashtable<Component,GridBagConstraints> comptable
comptable are the components and the
 values are the instances of GridBagConstraints.GridBagConstraintsprotected GridBagConstraints defaultConstraints
defaultConstraints.protected GridBagLayoutInfo layoutInfo
layoutInfo is null
 this indicates that there are no components in
 the gridbag or if there are components, they have
 not yet been validated.getLayoutInfo(Container, int)public int[] columnWidths
null the values are
 applied to the gridbag after all of the minimum columns
 widths have been calculated.
 If columnWidths has more elements than the number of
 columns, columns are added to the gridbag to match
 the number of elements in columnWidth.getLayoutDimensions()public int[] rowHeights
null the values are
 applied to the gridbag after all of the minimum row
 heights have been calculated.
 If rowHeights has more elements than the number of
 rows, rows are added to the gridbag to match
 the number of elements in rowHeights.getLayoutDimensions()public double[] columnWeights
null the values are
 applied to the gridbag after all of the columns
 weights have been calculated.
 If columnWeights[i] > weight for column i, then
 column i is assigned the weight in columnWeights[i].
 If columnWeights has more elements than the number
 of columns, the excess elements are ignored - they do
 not cause more columns to be created.public double[] rowWeights
null the values are
 applied to the gridbag after all of the rows
 weights have been calculated.
 If rowWeights[i] > weight for row i, then
 row i is assigned the weight in rowWeights[i].
 If rowWeights has more elements than the number
 of rows, the excess elements are ignored - they do
 not cause more rows to be created.public void setConstraints(Component comp, GridBagConstraints constraints)
comp - the component to be modifiedconstraints - the constraints to be appliedpublic GridBagConstraints getConstraints(Component comp)
GridBagConstraints object is returned.comp - the component to be queriedprotected GridBagConstraints lookupConstraints(Component comp)
GridBagConstraints object used by the layout mechanism.
 
 If comp is not in the GridBagLayout,
 a set of default GridBagConstraints are returned.
 A comp value of null is invalid
 and returns null.
comp - the component to be queriedpublic Point getLayoutOrigin()
ComponentOrientation value of the container.  This
 is distinct from the grid origin given by the cell coordinates (0,0).
 Most applications do not call this method directly.ComponentOrientationpublic int[][] getLayoutDimensions()
Most applications do not call this method directly.
public double[][] getLayoutWeights()
Most applications do not call this method directly.
public Point location(int x, int y)
(x, y). Each cell is identified
 by its column index (ranging from 0 to the number of columns
 minus 1) and its row index (ranging from 0 to the number of
 rows minus 1).
 
 If the (x, y) point lies
 outside the grid, the following rules are used.
 The column index is returned as zero if x lies to the
 left of the layout for a left-to-right container or to the right of
 the layout for a right-to-left container.  The column index is returned
 as the number of columns if x lies
 to the right of the layout in a left-to-right container or to the left
 in a right-to-left container.
 The row index is returned as zero if y lies above the
 layout, and as the number of rows if y lies
 below the layout.  The orientation of a container is determined by its
 ComponentOrientation property.
x - the x coordinate of a pointy - the y coordinate of a pointComponentOrientationpublic void addLayoutComponent(String name, Component comp)
addLayoutComponent in interface LayoutManagername - the string to be associated with the componentcomp - the component to be addedpublic void addLayoutComponent(Component comp, Object constraints)
constraints object.  Note that constraints
 are mutable and are, therefore, cloned when cached.addLayoutComponent in interface LayoutManager2comp - the component to be addedconstraints - an object that determines how
                          the component is added to the layoutIllegalArgumentException - if constraints
            is not a GridBagConstraintpublic void removeLayoutComponent(Component comp)
Most applications do not call this method directly.
removeLayoutComponent in interface LayoutManagercomp - the component to be removed.Container.remove(java.awt.Component), 
Container.removeAll()public Dimension preferredLayoutSize(Container parent)
parent
 container using this grid bag layout.
 Most applications do not call this method directly.
preferredLayoutSize in interface LayoutManagerparent - the container in which to do the layoutparent
  containerContainer.getPreferredSize()public Dimension minimumLayoutSize(Container parent)
parent container
 using this grid bag layout.
 Most applications do not call this method directly.
minimumLayoutSize in interface LayoutManagerparent - the container in which to do the layoutparent containerContainer.doLayout()public Dimension maximumLayoutSize(Container target)
maximumLayoutSize in interface LayoutManager2target - the container which needs to be laid outContainer, 
minimumLayoutSize(Container), 
preferredLayoutSize(Container)public float getLayoutAlignmentX(Container parent)
getLayoutAlignmentX in interface LayoutManager20.5f to indicate centeredpublic float getLayoutAlignmentY(Container parent)
getLayoutAlignmentY in interface LayoutManager20.5f to indicate centeredpublic void invalidateLayout(Container target)
invalidateLayout in interface LayoutManager2public void layoutContainer(Container parent)
GridBagLayout
 object.
 Most applications do not call this method directly.
layoutContainer in interface LayoutManagerparent - the container in which to do the layoutContainer, 
Container.doLayout()public String toString()
protected GridBagLayoutInfo getLayoutInfo(Container parent, int sizeflag)
GridBagLayoutInfo for the
 current set of managed children. This requires three passes through the
 set of children:
 
 This method should only be used internally by
 GridBagLayout.
parent - the layout containersizeflag - either PREFERREDSIZE or
   MINSIZEGridBagLayoutInfo for the set of childrenprotected GridBagLayoutInfo GetLayoutInfo(Container parent, int sizeflag)
getLayoutInfo instead.
 This method is the same as getLayoutInfo;
 refer to getLayoutInfo for details on parameters
 and return value.protected void adjustForGravity(GridBagConstraints constraints, Rectangle r)
GridBagLayout.constraints - the constraints to be appliedr - the Rectangle to be adjustedprotected void AdjustForGravity(GridBagConstraints constraints, Rectangle r)
adjustForGravity instead.
 This method is the same as adjustForGravity;
 refer to adjustForGravity for details
 on parameters.protected Dimension getMinSize(Container parent, GridBagLayoutInfo info)
getLayoutInfo.
 This method should only be used internally by
 GridBagLayout.parent - the layout containerinfo - the layout info for this parentDimension object containing the
   minimum sizeprotected Dimension GetMinSize(Container parent, GridBagLayoutInfo info)
getMinSize instead.
 This method is the same as getMinSize;
 refer to getMinSize for details on parameters
 and return value.protected void arrangeGrid(Container parent)
GridBagLayout.parent - the layout containerprotected void ArrangeGrid(Container parent)
arrangeGrid instead.
 This method is the same as arrangeGrid;
 refer to arrangeGrid for details on the
 parameter. Submit a bug or feature 
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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