java.lang.Objectjavax.swing.SpringLayout
public class SpringLayout
A 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 uses SpringLayout, 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 Boxes. 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 TM has been added to the java.beans package. Please see XMLEncoder .
Nested Class Summary | |
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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. |
Field Summary | |
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static String |
EAST
Specifies the right edge of a component's bounding rectangle. |
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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. |
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static String |
WEST
Specifies the left edge of a component's bounding rectangle. |
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Constructor Summary | |
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SpringLayout
() Constructs a new SpringLayout. |
Method Summary | |
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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. |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Field Detail |
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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
Constructor Detail |
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public SpringLayout()
Method Detail |
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public void addLayoutComponent(String name, Component c)
public void removeLayoutComponent(Component c)
public Dimension minimumLayoutSize(Container parent)
public Dimension preferredLayoutSize(Container parent)
public Dimension maximumLayoutSize(Container parent)
public void addLayoutComponent(Component component, Object constraints)
public float getLayoutAlignmentX(Container p)
public float getLayoutAlignmentY(Container p)
public void invalidateLayout(Container p)
public void putConstraint(String e1, Component c1, int pad, String e2, Component c2)
value(e1, c1) = value(e2, c2) + padto take place during all subsequent layout operations.
public void putConstraint(String e1, Component c1, Spring s, String e2, Component c2)
public SpringLayout.Constraints getConstraints(Component c)
public Spring getConstraint(String edgeName, Component c)
public void layoutContainer(Container parent)