LayoutManager
, LayoutManager2
, Serializable
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 FormModifier and Type | Field | Description |
---|---|---|
double[] |
columnWeights |
This field holds the overrides to the column weights.
|
int[] |
columnWidths |
This field holds the overrides to the column minimum
width.
|
protected Hashtable<Component,GridBagConstraints> |
comptable |
This hashtable maintains the association between
a component and its gridbag constraints.
|
protected GridBagConstraints |
defaultConstraints |
This 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 |
layoutInfo |
This field holds the layout information
for the gridbag.
|
protected static int |
MAXGRIDSIZE |
This field is no longer used to reserve arrays and kept for backward
compatibility.
|
protected static int |
MINSIZE |
The smallest grid that can be laid out by the grid bag layout.
|
protected static int |
PREFERREDSIZE |
The preferred grid size that can be laid out by the grid bag layout.
|
int[] |
rowHeights |
This field holds the overrides to the row minimum
heights.
|
double[] |
rowWeights |
This field holds the overrides to the row weights.
|
Constructor | Description |
---|---|
GridBagLayout() |
Creates a grid bag layout manager.
|
Modifier and Type | Method | Description |
---|---|---|
void |
addLayoutComponent(Component comp,
Object constraints) |
Adds the specified component to the layout, using the specified
constraints object. |
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) |
Adjusts the x, y, width, and height fields to the correct
values depending on the constraint geometry and pads.
|
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
arrangeGrid instead. |
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
GridBagLayoutInfo for 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
getLayoutInfo instead. |
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
getMinSize instead. |
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
parent container
using this grid bag layout. |
Dimension |
preferredLayoutSize(Container parent) |
Determines the preferred size of the
parent
container 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
.GridBagConstraints
protected 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.ComponentOrientation
public 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 pointComponentOrientation
public void addLayoutComponent(String name, Component comp)
addLayoutComponent
in interface LayoutManager
name
- 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 LayoutManager2
comp
- the component to be addedconstraints
- an object that determines how
the component is added to the layoutIllegalArgumentException
- if constraints
is not a GridBagConstraint
public void removeLayoutComponent(Component comp)
Most applications do not call this method directly.
removeLayoutComponent
in interface LayoutManager
comp
- 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 LayoutManager
parent
- 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 LayoutManager
parent
- the container in which to do the layoutparent
containerContainer.doLayout()
public Dimension maximumLayoutSize(Container target)
maximumLayoutSize
in interface LayoutManager2
target
- the container which needs to be laid outContainer
,
minimumLayoutSize(Container)
,
preferredLayoutSize(Container)
public float getLayoutAlignmentX(Container parent)
getLayoutAlignmentX
in interface LayoutManager2
parent
- the target container0.5f
to indicate centeredpublic float getLayoutAlignmentY(Container parent)
getLayoutAlignmentY
in interface LayoutManager2
parent
- the target container0.5f
to indicate centeredpublic void invalidateLayout(Container target)
invalidateLayout
in interface LayoutManager2
target
- the target containerpublic void layoutContainer(Container parent)
GridBagLayout
object.
Most applications do not call this method directly.
layoutContainer
in interface LayoutManager
parent
- 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
MINSIZE
GridBagLayoutInfo
for the set of childrenprotected GridBagLayoutInfo GetLayoutInfo(Container parent, int sizeflag)
getLayoutInfo
instead.
Fills in an instance of GridBagLayoutInfo
for the
current set of managed children. This method is the same
as getLayoutInfo
; refer to getLayoutInfo
description for details.parent
- the layout containersizeflag
- either PREFERREDSIZE
or MINSIZE
GridBagLayoutInfo
for the set of childrenprotected void adjustForGravity(GridBagConstraints constraints, Rectangle r)
GridBagLayout
.constraints
- the constraints to be appliedr
- the Rectangle
to be adjustedprotected void AdjustForGravity(GridBagConstraints constraints, Rectangle r)
This method is obsolete and supplied for backwards
compatibility only; new code should call adjustForGravity
instead.
This method is the same as adjustForGravity
constraints
- the constraints to be appliedr
- the Rectangle
to be adjustedprotected 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
parent
- the layout containerinfo
- the layout info for this parentDimension
object containing the
minimum sizeprotected void arrangeGrid(Container parent)
GridBagLayout
.parent
- the layout containerprotected void ArrangeGrid(Container parent)
arrangeGrid
instead.
This method is the same as arrangeGrid
parent
- the layout container 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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