| java.lang.Object java.awt.GridBagLayout
GridBagLayout | public class GridBagLayout implements LayoutManager2,java.io.Serializable(Code) | | The 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
- Specifies the cell containing the leading corner of the component's
display area, where the cell at the origin of the grid has address
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
- Specifies the number of cells in a row (for
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
- Used when the component's display area
is larger than the component's requested size
to determine whether (and how) to resize the component.
Possible values are
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
- Specifies the component's internal padding within the layout,
how much to add to the minimum size of the component.
The width of the component will be at least its minimum width
plus
ipadx pixels. Similarly, the height of
the component will be at least the minimum height plus
ipady pixels.
-
GridBagConstraints.insets
- Specifies the component's external padding, the minimum
amount of space between the component and the edges of its display area.
-
GridBagConstraints.anchor
- Specifies where the component should be positioned in its display area.
There are three kinds of possible values: absolute, orientation-relative,
and baseline-relative
Orientation relative values are interpreted relative to the container's
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.NORTH
GridBagConstraints.SOUTH
GridBagConstraints.WEST
GridBagConstraints.EAST
GridBagConstraints.NORTHWEST
GridBagConstraints.NORTHEAST
GridBagConstraints.SOUTHWEST
GridBagConstraints.SOUTHEAST
GridBagConstraints.CENTER (the default)
|
GridBagConstraints.PAGE_START
GridBagConstraints.PAGE_END
GridBagConstraints.LINE_START
GridBagConstraints.LINE_END
GridBagConstraints.FIRST_LINE_START
GridBagConstraints.FIRST_LINE_END
GridBagConstraints.LAST_LINE_START
GridBagConstraints.LAST_LINE_END
|
GridBagConstraints.BASELINE
GridBagConstraints.BASELINE_LEADING
GridBagConstraints.BASELINE_TRAILING
GridBagConstraints.ABOVE_BASELINE
GridBagConstraints.ABOVE_BASELINE_LEADING
GridBagConstraints.ABOVE_BASELINE_TRAILING
GridBagConstraints.BELOW_BASELINE
GridBagConstraints.BELOW_BASELINE_LEADING
GridBagConstraints.BELOW_BASELINE_TRAILING
|
-
GridBagConstraints.weightx ,
GridBagConstraints.weighty
- Used to determine how to distribute space, which is
important for specifying resizing behavior.
Unless you specify a weight for at least one component
in a row (
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:
This layout consists of three components:
- A panel that starts in row 0 and ends in row 1. The panel
has a baseline-resize behavior of
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.
- Two buttons, each with a baseline-resize behavior of
CENTER_OFFSET and an anchor of BASELINE .
Because the second button and the panel share the same prevailing row,
they are both aligned along their 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:
- Resizable components positioned above the baseline can only
grow as tall as the baseline. For example, if the baseline is at 100
and anchored at the top, a resizable component positioned above the
baseline can never grow more than 100 units.
- Similarly, resizable components positioned below the baseline can
only grow as high as the difference between the display height and the
baseline.
- Resizable components positioned on the baseline with a
baseline-resize behavior of
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.
- Components positioned on the baseline that do not have a
baseline-resize behavior of
OTHER
can only grow as tall as
display height - baseline + baseline of component .
If you position a component along the baseline, but the
component does not have a valid baseline, it will be vertically centered
in its space. Similarly if you have positioned a component relative
to the baseline and none of the components in the row have a valid
baseline the component is vertically centered.
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:
- Button1, Button2, Button3:
weightx = 1.0
- Button4:
weightx = 1.0 ,
gridwidth = GridBagConstraints.REMAINDER
- Button5:
gridwidth = GridBagConstraints.REMAINDER
- Button6:
gridwidth = GridBagConstraints.RELATIVE
- Button7:
gridwidth = GridBagConstraints.REMAINDER
- Button8:
gridheight = 2 ,
weighty = 1.0
- Button9, Button 10:
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();
}
}
version: 1.85, 05/05/07 author: Doug Stein author: Bill Spitzak (orignial NeWS & OLIT implementation) See Also: java.awt.GridBagConstraints See Also: java.awt.GridBagLayoutInfo See Also: java.awt.ComponentOrientation since: JDK1.0 |
Field Summary | |
final static int | EMPIRICMULTIPLIER | final protected static int | MAXGRIDSIZE This field is no longer used to reserve arrays and keeped for backward
compatibility. | final protected static int | MINSIZE The smallest grid that can be laid out by the grid bag layout. | final protected static int | PREFERREDSIZE The preferred grid size that can be laid out by the grid bag layout. | public double | columnWeights This field holds the overrides to the column weights. | public 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. | transient boolean | rightToLeft | public int | rowHeights This field holds the overrides to the row minimum
heights. | public double | rowWeights This field holds the overrides to the row weights. | final static long | serialVersionUID |
Constructor Summary | |
public | GridBagLayout() Creates a grid bag layout manager. |
Method Summary | |
protected void | AdjustForGravity(GridBagConstraints constraints, Rectangle r) This method is obsolete and supplied for backwards
compatability only; new code should call
GridBagLayout.adjustForGravity(java.awt.GridBagConstraints,java.awt.Rectangle)adjustForGravity instead. | protected void | ArrangeGrid(Container parent) This method is obsolete and supplied for backwards
compatability only; new code should call
GridBagLayout.arrangeGrid(Container) arrangeGrid instead. | protected GridBagLayoutInfo | GetLayoutInfo(Container parent, int sizeflag) This method is obsolete and supplied for backwards
compatability only; new code should call
GridBagLayout.getLayoutInfo(java.awt.Container,int) getLayoutInfo instead. | protected Dimension | GetMinSize(Container parent, GridBagLayoutInfo info) This method is obsolete and supplied for backwards
compatability only; new code should call
GridBagLayout.getMinSize(java.awt.Container,GridBagLayoutInfo) getMinSize instead. | public void | addLayoutComponent(String name, Component comp) Has no effect, since this layout manager does not use a per-component string. | public void | addLayoutComponent(Component comp, Object constraints) Adds the specified component to the layout, using the specified
constraints object. | 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. | public GridBagConstraints | getConstraints(Component comp) Gets the constraints for the specified component. | public float | getLayoutAlignmentX(Container parent) Returns the alignment along the x axis. | public float | getLayoutAlignmentY(Container parent) Returns the alignment along the y axis. | public 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. | public Point | getLayoutOrigin() Determines the origin of the layout area, in the graphics coordinate
space of the target container. | public 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 . | public void | invalidateLayout(Container target) Invalidates the layout, indicating that if the layout manager
has cached information it should be discarded. | public void | layoutContainer(Container parent) Lays out the specified container using this grid bag layout. | public 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. | public Dimension | maximumLayoutSize(Container target) Returns the maximum dimensions for this layout given the components
in the specified target container. | public Dimension | minimumLayoutSize(Container parent) Determines the minimum size of the parent container
using this grid bag layout. | public Dimension | preferredLayoutSize(Container parent) Determines the preferred size of the parent
container using this grid bag layout. | public void | removeLayoutComponent(Component comp) Removes the specified component from this layout. | public void | setConstraints(Component comp, GridBagConstraints constraints) Sets the constraints for the specified component in this layout. | public String | toString() Returns a string representation of this grid bag layout's values. |
EMPIRICMULTIPLIER | final static int EMPIRICMULTIPLIER(Code) | | |
MAXGRIDSIZE | final protected static int MAXGRIDSIZE(Code) | | This field is no longer used to reserve arrays and keeped for backward
compatibility. Previously, this was
the maximum number of grid positions (both horizontal and
vertical) that could be laid out by the grid bag layout.
Current implementation doesn't impose any limits
on the size of a grid.
|
MINSIZE | final protected static int MINSIZE(Code) | | The smallest grid that can be laid out by the grid bag layout.
|
PREFERREDSIZE | final protected static int PREFERREDSIZE(Code) | | The preferred grid size that can be laid out by the grid bag layout.
|
columnWeights | public double columnWeights(Code) | | This field holds the overrides to the column weights.
If this field is non-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.
|
columnWidths | public int columnWidths(Code) | | This field holds the overrides to the column minimum
width. If this field is non-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.
See Also: GridBagLayout.getLayoutDimensions() |
layoutInfo | protected GridBagLayoutInfo layoutInfo(Code) | | This field holds the layout information
for the gridbag. The information in this field
is based on the most recent validation of the
gridbag.
If layoutInfo is null
this indicates that there are no components in
the gridbag or if there are components, they have
not yet been validated.
See Also: GridBagLayout.getLayoutInfo(Container,int) |
rightToLeft | transient boolean rightToLeft(Code) | | |
rowHeights | public int rowHeights(Code) | | This field holds the overrides to the row minimum
heights. If this field is non-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, rowa are added to the gridbag to match
the number of elements in rowHeights .
See Also: GridBagLayout.getLayoutDimensions() |
rowWeights | public double rowWeights(Code) | | This field holds the overrides to the row weights.
If this field is non-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.
|
serialVersionUID | final static long serialVersionUID(Code) | | |
GridBagLayout | public GridBagLayout()(Code) | | Creates a grid bag layout manager.
|
ArrangeGrid | protected void ArrangeGrid(Container parent)(Code) | | This method is obsolete and supplied for backwards
compatability only; new code should call
GridBagLayout.arrangeGrid(Container) arrangeGrid instead.
This method is the same as arrangeGrid ;
refer to arrangeGrid for details on the
parameter.
|
addLayoutComponent | public void addLayoutComponent(String name, Component comp)(Code) | | Has no effect, since this layout manager does not use a per-component string.
|
addLayoutComponent | public void addLayoutComponent(Component comp, Object constraints)(Code) | | Adds the specified component to the layout, using the specified
constraints object. Note that constraints
are mutable and are, therefore, cloned when cached.
Parameters: comp - the component to be added Parameters: constraints - an object that determines howthe component is added to the layout exception: IllegalArgumentException - if constraints is not a GridBagConstraint |
adjustForGravity | protected void adjustForGravity(GridBagConstraints constraints, Rectangle r)(Code) | | Adjusts the x, y, width, and height fields to the correct
values depending on the constraint geometry and pads.
This method should only be used internally by
GridBagLayout .
Parameters: constraints - the constraints to be applied Parameters: r - the Rectangle to be adjusted since: 1.4 |
arrangeGrid | protected void arrangeGrid(Container parent)(Code) | | Lays out the grid.
This method should only be used internally by
GridBagLayout .
Parameters: parent - the layout container since: 1.4 |
getConstraints | public GridBagConstraints getConstraints(Component comp)(Code) | | Gets the constraints for the specified component. A copy of
the actual GridBagConstraints object is returned.
Parameters: comp - the component to be queried the constraint for the specified component in thisgrid bag layout; a copy of the actual constraintobject is returned |
getLayoutAlignmentX | public float getLayoutAlignmentX(Container parent)(Code) | | 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.
the value 0.5f to indicate centered |
getLayoutAlignmentY | public float getLayoutAlignmentY(Container parent)(Code) | | 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.
the value 0.5f to indicate centered |
getLayoutDimensions | public int[][] getLayoutDimensions()(Code) | | Determines column widths and row heights for the layout grid.
Most applications do not call this method directly.
an array of two arrays, containing the widthsof the layout columns andthe heights of the layout rows since: JDK1.1 |
getLayoutInfo | protected GridBagLayoutInfo getLayoutInfo(Container parent, int sizeflag)(Code) | | Fills in an instance of GridBagLayoutInfo for the
current set of managed children. This requires three passes through the
set of children:
- Figure out the dimensions of the layout grid.
- Determine which cells the components occupy.
- Distribute the weights and min sizes amoung the rows/columns.
This also caches the minsizes for all the children when they are
first encountered (so subsequent loops don't need to ask again).
This method should only be used internally by
GridBagLayout .
Parameters: parent - the layout container Parameters: sizeflag - either PREFERREDSIZE orMINSIZE the GridBagLayoutInfo for the set of children since: 1.4 |
getLayoutOrigin | public Point getLayoutOrigin()(Code) | | Determines the origin of the layout area, in the graphics coordinate
space of the target container. This value represents the pixel
coordinates of the top-left corner of the layout area regardless of
the 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.
the graphics origin of the cell in the top-leftcorner of the layout grid See Also: java.awt.ComponentOrientation since: JDK1.1 |
getLayoutWeights | public double[][] getLayoutWeights()(Code) | | Determines the weights of the layout grid's columns and rows.
Weights are used to calculate how much a given column or row
stretches beyond its preferred size, if the layout has extra
room to fill.
Most applications do not call this method directly.
an array of two arrays, representing thehorizontal weights of the layout columnsand the vertical weights of the layout rows since: JDK1.1 |
getMinSize | protected Dimension getMinSize(Container parent, GridBagLayoutInfo info)(Code) | | Figures out the minimum size of the
master based on the information from getLayoutInfo .
This method should only be used internally by
GridBagLayout .
Parameters: parent - the layout container Parameters: info - the layout info for this parent a Dimension object containing theminimum size since: 1.4 |
invalidateLayout | public void invalidateLayout(Container target)(Code) | | Invalidates the layout, indicating that if the layout manager
has cached information it should be discarded.
|
layoutContainer | public void layoutContainer(Container parent)(Code) | | Lays out the specified container using this grid bag layout.
This method reshapes components in the specified container in
order to satisfy the contraints of this GridBagLayout
object.
Most applications do not call this method directly.
Parameters: parent - the container in which to do the layout See Also: java.awt.Container See Also: java.awt.Container.doLayout |
location | public Point location(int x, int y)(Code) | | Determines which cell in the layout grid contains the point
specified by (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.
Parameters: x - the x coordinate of a point Parameters: y - the y coordinate of a point an ordered pair of indexes that indicate which cellin the layout grid contains the point(x, y). See Also: java.awt.ComponentOrientation since: JDK1.1 |
lookupConstraints | protected GridBagConstraints lookupConstraints(Component comp)(Code) | | Retrieves the constraints for the specified component.
The return value is not a copy, but is the actual
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 .
Parameters: comp - the component to be queried the contraints for the specified component |
minimumLayoutSize | public Dimension minimumLayoutSize(Container parent)(Code) | | Determines the minimum size of the parent container
using this grid bag layout.
Most applications do not call this method directly.
Parameters: parent - the container in which to do the layout See Also: java.awt.Container.doLayout the minimum size of the parent container |
preferredLayoutSize | public Dimension preferredLayoutSize(Container parent)(Code) | | Determines the preferred size of the parent
container using this grid bag layout.
Most applications do not call this method directly.
Parameters: parent - the container in which to do the layout See Also: java.awt.Container.getPreferredSize the preferred size of the parent container |
setConstraints | public void setConstraints(Component comp, GridBagConstraints constraints)(Code) | | Sets the constraints for the specified component in this layout.
Parameters: comp - the component to be modified Parameters: constraints - the constraints to be applied |
toString | public String toString()(Code) | | Returns a string representation of this grid bag layout's values.
a string representation of this grid bag layout. |
|
|