LayoutManager
, LayoutManager2
public class SpringLayout extends Object implements LayoutManager2
SpringLayout
lays out the children of its associated container
according to a set of constraints.
See How to Use SpringLayout
in The Java Tutorial for examples of using
SpringLayout
.
Each constraint,
represented by a Spring
object,
controls the vertical or horizontal distance
between two component edges.
The edges can belong to
any child of the container,
or to the container itself.
For example,
the allowable width of a component
can be expressed using a constraint
that controls the distance between the west (left) and east (right)
edges of the component.
The allowable y coordinates for a component
can be expressed by constraining the distance between
the north (top) edge of the component
and the north edge of its container.
Every child of a SpringLayout
-controlled container,
as well as the container itself,
has exactly one set of constraints
associated with it.
These constraints are represented by
a SpringLayout.Constraints
object.
By default,
SpringLayout
creates constraints
that make their associated component
have the minimum, preferred, and maximum sizes
returned by the component's
Component.getMinimumSize()
,
Component.getPreferredSize()
, and
Component.getMaximumSize()
methods. The x and y positions are initially not
constrained, so that until you constrain them the Component
will be positioned at 0,0 relative to the Insets
of the
parent Container
.
You can change
a component's constraints in several ways.
You can
use one of the
putConstraint
methods
to establish a spring
linking the edges of two components within the same container.
Or you can get the appropriate SpringLayout.Constraints
object using
getConstraints
and then modify one or more of its springs.
Or you can get the spring for a particular edge of a component
using getConstraint
,
and modify it.
You can also associate
your own SpringLayout.Constraints
object
with a component by specifying the constraints object
when you add the component to its container
(using
Container.add(Component, Object)
).
The Spring
object representing each constraint
has a minimum, preferred, maximum, and current value.
The current value of the spring
is somewhere between the minimum and maximum values,
according to the formula given in the
Spring.sum(javax.swing.Spring, javax.swing.Spring)
method description.
When the minimum, preferred, and maximum values are the same,
the current value is always equal to them;
this inflexible spring is called a strut.
You can create struts using the factory method
Spring.constant(int)
.
The Spring
class also provides factory methods
for creating other kinds of springs,
including springs that depend on other springs.
In a SpringLayout
, the position of each edge is dependent on
the position of just one other edge. If a constraint is subsequently added
to create a new binding for an edge, the previous binding is discarded
and the edge remains dependent on a single edge.
Springs should only be attached
between edges of the container and its immediate children; the behavior
of the SpringLayout
when presented with constraints linking
the edges of components from different containers (either internal or
external) is undefined.
Note: Unlike many layout managers,SpringLayout
doesn't automatically set the location of the components it manages. If you hand-code a GUI that usesSpringLayout
, remember to initialize component locations by constraining the west/east and north/south locations.Depending on the constraints you use, you may also need to set the size of the container explicitly.
Despite the simplicity of SpringLayout
,
it can emulate the behavior of most other layout managers.
For some features,
such as the line breaking provided by FlowLayout
,
you'll need to
create a special-purpose subclass of the Spring
class.
SpringLayout
also provides a way to solve
many of the difficult layout
problems that cannot be solved by nesting combinations
of Box
es. That said, SpringLayout
honors the
LayoutManager2
contract correctly and so can be nested with
other layout managers -- a technique that can be preferable to
creating the constraints implied by the other layout managers.
The asymptotic complexity of the layout operation of a SpringLayout
is linear in the number of constraints (and/or components).
Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing. As of 1.4, support for long term storage
of all JavaBeans™
has been added to the java.beans
package.
Please see XMLEncoder
.
Spring
,
SpringLayout.Constraints
Modifier and Type | Class | Description |
---|---|---|
static class |
SpringLayout.Constraints |
A
Constraints object holds the
constraints that govern the way a component's size and position
change in a container controlled by a SpringLayout . |
Modifier and Type | Field | Description |
---|---|---|
static String |
BASELINE |
Specifies the baseline of a component.
|
static String |
EAST |
Specifies the right edge of a component's bounding rectangle.
|
static String |
HEIGHT |
Specifies the height of a component's bounding rectangle.
|
static String |
HORIZONTAL_CENTER |
Specifies the horizontal center of a component's bounding rectangle.
|
static String |
NORTH |
Specifies the top edge of a component's bounding rectangle.
|
static String |
SOUTH |
Specifies the bottom edge of a component's bounding rectangle.
|
static String |
VERTICAL_CENTER |
Specifies the vertical center of a component's bounding rectangle.
|
static String |
WEST |
Specifies the left edge of a component's bounding rectangle.
|
static String |
WIDTH |
Specifies the width of a component's bounding rectangle.
|
Constructor | Description |
---|---|
SpringLayout() |
Constructs a new
SpringLayout . |
Modifier and Type | Method | Description |
---|---|---|
void |
addLayoutComponent(Component component,
Object constraints) |
If
constraints is an instance of
SpringLayout.Constraints ,
associates the constraints with the specified component. |
void |
addLayoutComponent(String name,
Component c) |
Has no effect,
since this layout manager does not
use a per-component string.
|
Spring |
getConstraint(String edgeName,
Component c) |
Returns the spring controlling the distance between
the specified edge of
the component and the top or left edge of its parent.
|
SpringLayout.Constraints |
getConstraints(Component c) |
Returns the constraints for the specified component.
|
float |
getLayoutAlignmentX(Container p) |
Returns 0.5f (centered).
|
float |
getLayoutAlignmentY(Container p) |
Returns 0.5f (centered).
|
void |
invalidateLayout(Container p) |
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.
|
Dimension |
maximumLayoutSize(Container parent) |
Calculates the maximum size dimensions for the specified container,
given the components it contains.
|
Dimension |
minimumLayoutSize(Container parent) |
Calculates the minimum size dimensions for the specified
container, given the components it contains.
|
Dimension |
preferredLayoutSize(Container parent) |
Calculates the preferred size dimensions for the specified
container, given the components it contains.
|
void |
putConstraint(String e1,
Component c1,
int pad,
String e2,
Component c2) |
Links edge
e1 of component c1 to
edge e2 of component c2 ,
with a fixed distance between the edges. |
void |
putConstraint(String e1,
Component c1,
Spring s,
String e2,
Component c2) |
Links edge
e1 of component c1 to
edge e2 of component c2 . |
void |
removeLayoutComponent(Component c) |
Removes the constraints associated with the specified component.
|
public static final String NORTH
public static final String SOUTH
public static final String EAST
public static final String WEST
public static final String HORIZONTAL_CENTER
public static final String VERTICAL_CENTER
public static final String BASELINE
public static final String WIDTH
public static final String HEIGHT
public void addLayoutComponent(String name, Component c)
addLayoutComponent
in interface LayoutManager
name
- the string to be associated with the componentc
- the component to be addedpublic void removeLayoutComponent(Component c)
removeLayoutComponent
in interface LayoutManager
c
- the component being removed from the containerpublic Dimension minimumLayoutSize(Container parent)
LayoutManager
minimumLayoutSize
in interface LayoutManager
parent
- the component to be laid outLayoutManager.preferredLayoutSize(java.awt.Container)
public Dimension preferredLayoutSize(Container parent)
LayoutManager
preferredLayoutSize
in interface LayoutManager
parent
- the container to be laid outLayoutManager.minimumLayoutSize(java.awt.Container)
public Dimension maximumLayoutSize(Container parent)
LayoutManager2
maximumLayoutSize
in interface LayoutManager2
parent
- the target containerComponent.getMaximumSize()
,
LayoutManager
public void addLayoutComponent(Component component, Object constraints)
constraints
is an instance of
SpringLayout.Constraints
,
associates the constraints with the specified component.addLayoutComponent
in interface LayoutManager2
component
- the component being addedconstraints
- the component's constraintsSpringLayout.Constraints
public float getLayoutAlignmentX(Container p)
getLayoutAlignmentX
in interface LayoutManager2
p
- the target containerpublic float getLayoutAlignmentY(Container p)
getLayoutAlignmentY
in interface LayoutManager2
p
- the target containerpublic void invalidateLayout(Container p)
LayoutManager2
invalidateLayout
in interface LayoutManager2
p
- the target containerpublic void putConstraint(String e1, Component c1, int pad, String e2, Component c2)
e1
of component c1
to
edge e2
of component c2
,
with a fixed distance between the edges. This
constraint will cause the assignment
value(e1, c1) = value(e2, c2) + padto take place during all subsequent layout operations.
e1
- the edge of the dependentc1
- the component of the dependentpad
- the fixed distance between dependent and anchore2
- the edge of the anchorc2
- the component of the anchorputConstraint(String, Component, Spring, String, Component)
public void putConstraint(String e1, Component c1, Spring s, String e2, Component c2)
e1
of component c1
to
edge e2
of component c2
. As edge
(e2, c2)
changes value, edge (e1, c1)
will
be calculated by taking the (spring) sum of (e2, c2)
and s
.
Each edge must have one of the following values:
SpringLayout.NORTH
,
SpringLayout.SOUTH
,
SpringLayout.EAST
,
SpringLayout.WEST
,
SpringLayout.VERTICAL_CENTER
,
SpringLayout.HORIZONTAL_CENTER
or
SpringLayout.BASELINE
.e1
- the edge of the dependentc1
- the component of the dependents
- the spring linking dependent and anchore2
- the edge of the anchorc2
- the component of the anchorputConstraint(String, Component, int, String, Component)
,
NORTH
,
SOUTH
,
EAST
,
WEST
,
VERTICAL_CENTER
,
HORIZONTAL_CENTER
,
BASELINE
public SpringLayout.Constraints getConstraints(Component c)
GridBagLayout
getConstraints
method,
this method does not clone constraints.
If no constraints
have been associated with this component,
this method
returns a default constraints object positioned at
0,0 relative to the parent's Insets and its width/height
constrained to the minimum, maximum, and preferred sizes of the
component. The size characteristics
are not frozen at the time this method is called;
instead this method returns a constraints object
whose characteristics track the characteristics
of the component as they change.c
- the component whose constraints will be returnedpublic Spring getConstraint(String edgeName, Component c)
SpringLayout
so that
the layout operation always terminates.edgeName
- must be one of
SpringLayout.NORTH
,
SpringLayout.SOUTH
,
SpringLayout.EAST
,
SpringLayout.WEST
,
SpringLayout.VERTICAL_CENTER
,
SpringLayout.HORIZONTAL_CENTER
or
SpringLayout.BASELINE
c
- the component whose edge spring is desiredNORTH
,
SOUTH
,
EAST
,
WEST
,
VERTICAL_CENTER
,
HORIZONTAL_CENTER
,
BASELINE
public void layoutContainer(Container parent)
LayoutManager
layoutContainer
in interface LayoutManager
parent
- the container to be laid out 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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DRAFT 9-internal+0-adhoc.mlchung.jdk9-jdeps