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JavaTM 2 Platform Std. Ed. v1.3 |
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java.lang.Object | +--java.awt.GridBagLayout
The GridBagLayout class is a flexible layout
manager that aligns components vertically and horizontally,
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 grid bag layout is associated
with an instance of
GridBagConstraints
that specifies how the component is laid out within its display area.
How a GridBagLayout object places a set of components
depends on the GridBagConstraints object associated
with each component, and on the minimum size
and the preferred size of the components' containers.
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.
Use GridBagConstraints.RELATIVE (the default value)
to specify that the component be just placed
just to the right of (for gridx)
or just below (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 be the last one in its row (for gridwidth)
or column (for gridheight).
Use GridBagConstraints.RELATIVE to specify
that the component be the next to last one
in its row (for gridwidth)
or 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 * 2) pixels (since the padding
applies to both sides of the component). Similarly, the height of
the component will be at least the minimum height plus
(ipady * 2) pixels.
GridBagConstraints.insets
GridBagConstraints.anchor
GridBagConstraints.CENTER (the default),
GridBagConstraints.NORTH,
GridBagConstraints.NORTHEAST,
GridBagConstraints.EAST,
GridBagConstraints.SOUTHEAST,
GridBagConstraints.SOUTH,
GridBagConstraints.SOUTHWEST,
GridBagConstraints.WEST, and
GridBagConstraints.NORTHWEST.
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.
The following figure shows ten components (all buttons) managed by a grid bag layout:
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("Helvetica", 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, Serialized Form| Field Summary | |
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 |
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 java.awt.GridBagLayoutInfo |
layoutInfo
This field holds tha layout information for the gridbag. |
protected static int |
MAXGRIDSIZE
The maximum number of grid positions (both horizontally and vertically) that can be laid out by the grid bag layout. |
protected static int |
MINSIZE
The smallest grid that can be laid out by the grid bag layout. |
protected static int |
PREFERREDSIZE
|
int[] |
rowHeights
This field holds the overrides to the row minimum heights. |
double[] |
rowWeights
This field holds the overrides to the row weights. |
| Constructor Summary | |
GridBagLayout()
Creates a grid bag layout manager. |
|
| Method Summary | |
void |
addLayoutComponent(Component comp,
Object constraints)
Adds the specified component to the layout, using the specified constraint object. |
void |
addLayoutComponent(String name,
Component comp)
Adds the specified component with the specified name to the layout. |
protected void |
AdjustForGravity(GridBagConstraints constraints,
Rectangle r)
|
protected void |
ArrangeGrid(Container parent)
|
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 java.awt.GridBagLayoutInfo |
GetLayoutInfo(Container parent,
int sizeflag)
Print the layout constraints. |
Point |
getLayoutOrigin()
Determines the origin of the layout grid. |
double[][] |
getLayoutWeights()
Determines the weights of the layout grid's columns and rows. |
protected Dimension |
GetMinSize(Container parent,
java.awt.GridBagLayoutInfo info)
|
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 target container
using this grid bag layout. |
Dimension |
preferredLayoutSize(Container parent)
Determines the preferred size of the target
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. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Field Detail |
protected static final int MAXGRIDSIZE
protected static final int MINSIZE
protected static final int PREFERREDSIZE
protected Hashtable comptable
GridBagConstraintsprotected GridBagConstraints defaultConstraints
defaultConstraints.getConstraints(Component),
setConstraints(Component, GridBagConstraints),
lookupConstraints(Component)protected java.awt.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
getLayoutDimensions()public int[] rowHeights
getLayoutDimensions()public double[] columnWeights
public double[] rowWeights
| Constructor Detail |
public GridBagLayout()
| Method Detail |
public void setConstraints(Component comp,
GridBagConstraints constraints)
comp - the component to be modified.constraints - the constraints to be applied.public GridBagConstraints getConstraints(Component comp)
GridBagConstraints object is returned.comp - the component to be queried.protected GridBagConstraints lookupConstraints(Component comp)
GridBagConstraints object used by the layout mechanism.comp - the component to be queriedpublic Point getLayoutOrigin()
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, and as the number of columns if x lies
to the right of the layout. 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.
x - the x coordinate of a point.y - the y coordinate of a point.
public void addLayoutComponent(String name,
Component comp)
addLayoutComponent in interface LayoutManagername - the name of the component.comp - the component to be added.
public void addLayoutComponent(Component comp,
Object constraints)
addLayoutComponent in interface LayoutManager2comp - the component to be added.constraints - an object that determines how
the component is added to the layout.public 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)
target
container using this grid bag layout.
Most applications do not call this method directly.
preferredLayoutSize in interface LayoutManagertarget - the container in which to do the layout.Container.getPreferredSize()public Dimension minimumLayoutSize(Container parent)
target container
using this grid bag layout.
Most applications do not call this method directly.
minimumLayoutSize in interface LayoutManagertarget - the container in which to do the layout.Container.doLayout()public Dimension maximumLayoutSize(Container target)
maximumLayoutSize in interface LayoutManager2target - the component which needs to be laid outContainer,
minimumLayoutSize(Container),
preferredLayoutSize(Container)public float getLayoutAlignmentX(Container parent)
getLayoutAlignmentX in interface LayoutManager2public float getLayoutAlignmentY(Container parent)
getLayoutAlignmentY in interface LayoutManager2public 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 layout.Container,
Container.doLayout()public String toString()
toString in class Object
protected java.awt.GridBagLayoutInfo GetLayoutInfo(Container parent,
int sizeflag)
protected void AdjustForGravity(GridBagConstraints constraints,
Rectangle r)
protected Dimension GetMinSize(Container parent,
java.awt.GridBagLayoutInfo info)
protected void ArrangeGrid(Container parent)
|
JavaTM 2 Platform Std. Ed. v1.3 |
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| SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | |||||||||
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