- java.lang.Object
-
- javax.swing.SpringLayout
-
- All Implemented Interfaces:
LayoutManager,LayoutManager2
public class SpringLayout extends Object implements LayoutManager2
ASpringLayoutlays 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 usingSpringLayout.Each constraint, represented by a
Springobject, 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 aSpringLayout.Constraintsobject. By default,SpringLayoutcreates constraints that make their associated component have the minimum, preferred, and maximum sizes returned by the component'sComponent.getMinimumSize(),Component.getPreferredSize(), andComponent.getMaximumSize()methods. The x and y positions are initially not constrained, so that until you constrain them theComponentwill be positioned at 0,0 relative to theInsetsof the parentContainer.You can change a component's constraints in several ways. You can use one of the
putConstraintmethods to establish a spring linking the edges of two components within the same container. Or you can get the appropriateSpringLayout.Constraintsobject usinggetConstraintsand then modify one or more of its springs. Or you can get the spring for a particular edge of a component usinggetConstraint, and modify it. You can also associate your ownSpringLayout.Constraintsobject with a component by specifying the constraints object when you add the component to its container (usingContainer.add(Component, Object)).The
Springobject 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 theSpring.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 methodSpring.constant(int). TheSpringclass 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 theSpringLayoutwhen presented with constraints linking the edges of components from different containers (either internal or external) is undefined.SpringLayout vs. Other Layout Managers
Note: Unlike many layout managers,SpringLayoutdoesn'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 byFlowLayout, you'll need to create a special-purpose subclass of theSpringclass.SpringLayoutalso provides a way to solve many of the difficult layout problems that cannot be solved by nesting combinations ofBoxes. That said,SpringLayouthonors theLayoutManager2contract 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
SpringLayoutis 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.beanspackage. Please seeXMLEncoder.- Since:
- 1.4
- See Also:
Spring,SpringLayout.Constraints
-
-
Nested Class Summary
Nested Classes Modifier and Type Class Description static classSpringLayout.ConstraintsAConstraintsobject holds the constraints that govern the way a component's size and position change in a container controlled by aSpringLayout.
-
Field Summary
Fields Modifier and Type Field Description static StringBASELINESpecifies the baseline of a component.static StringEASTSpecifies the right edge of a component's bounding rectangle.static StringHEIGHTSpecifies the height of a component's bounding rectangle.static StringHORIZONTAL_CENTERSpecifies the horizontal center of a component's bounding rectangle.static StringNORTHSpecifies the top edge of a component's bounding rectangle.static StringSOUTHSpecifies the bottom edge of a component's bounding rectangle.static StringVERTICAL_CENTERSpecifies the vertical center of a component's bounding rectangle.static StringWESTSpecifies the left edge of a component's bounding rectangle.static StringWIDTHSpecifies the width of a component's bounding rectangle.
-
Constructor Summary
Constructors Constructor Description SpringLayout()Constructs a newSpringLayout.
-
Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidaddLayoutComponent(Component component, Object constraints)Ifconstraintsis an instance ofSpringLayout.Constraints, associates the constraints with the specified component.voidaddLayoutComponent(String name, Component c)Has no effect, since this layout manager does not use a per-component string.SpringgetConstraint(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.ConstraintsgetConstraints(Component c)Returns the constraints for the specified component.floatgetLayoutAlignmentX(Container p)Returns 0.5f (centered).floatgetLayoutAlignmentY(Container p)Returns 0.5f (centered).voidputConstraint(String e1, Component c1, int pad, String e2, Component c2)Links edgee1of componentc1to edgee2of componentc2, with a fixed distance between the edges.voidputConstraint(String e1, Component c1, Spring s, String e2, Component c2)Links edgee1of componentc1to edgee2of componentc2.voidremoveLayoutComponent(Component c)Removes the constraints associated with the specified component.-
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
-
Methods declared in interface java.awt.LayoutManager
layoutContainer, minimumLayoutSize, preferredLayoutSize
-
Methods declared in interface java.awt.LayoutManager2
invalidateLayout, maximumLayoutSize
-
-
-
-
Field Detail
-
NORTH
public static final String NORTH
Specifies the top edge of a component's bounding rectangle.- See Also:
- Constant Field Values
-
SOUTH
public static final String SOUTH
Specifies the bottom edge of a component's bounding rectangle.- See Also:
- Constant Field Values
-
EAST
public static final String EAST
Specifies the right edge of a component's bounding rectangle.- See Also:
- Constant Field Values
-
WEST
public static final String WEST
Specifies the left edge of a component's bounding rectangle.- See Also:
- Constant Field Values
-
HORIZONTAL_CENTER
public static final String HORIZONTAL_CENTER
Specifies the horizontal center of a component's bounding rectangle.- Since:
- 1.6
- See Also:
- Constant Field Values
-
VERTICAL_CENTER
public static final String VERTICAL_CENTER
Specifies the vertical center of a component's bounding rectangle.- Since:
- 1.6
- See Also:
- Constant Field Values
-
BASELINE
public static final String BASELINE
Specifies the baseline of a component.- Since:
- 1.6
- See Also:
- Constant Field Values
-
WIDTH
public static final String WIDTH
Specifies the width of a component's bounding rectangle.- Since:
- 1.6
- See Also:
- Constant Field Values
-
HEIGHT
public static final String HEIGHT
Specifies the height of a component's bounding rectangle.- Since:
- 1.6
- See Also:
- Constant Field Values
-
-
Method Detail
-
addLayoutComponent
public void addLayoutComponent(String name, Component c)
Has no effect, since this layout manager does not use a per-component string.- Specified by:
addLayoutComponentin interfaceLayoutManager- Parameters:
name- the string to be associated with the componentc- the component to be added
-
removeLayoutComponent
public void removeLayoutComponent(Component c)
Removes the constraints associated with the specified component.- Specified by:
removeLayoutComponentin interfaceLayoutManager- Parameters:
c- the component being removed from the container
-
addLayoutComponent
public void addLayoutComponent(Component component, Object constraints)
Ifconstraintsis an instance ofSpringLayout.Constraints, associates the constraints with the specified component.- Specified by:
addLayoutComponentin interfaceLayoutManager2- Parameters:
component- the component being addedconstraints- the component's constraints- See Also:
SpringLayout.Constraints
-
getLayoutAlignmentX
public float getLayoutAlignmentX(Container p)
Returns 0.5f (centered).- Specified by:
getLayoutAlignmentXin interfaceLayoutManager2- Parameters:
p- the target container- Returns:
- the x-axis alignment preference
-
getLayoutAlignmentY
public float getLayoutAlignmentY(Container p)
Returns 0.5f (centered).- Specified by:
getLayoutAlignmentYin interfaceLayoutManager2- Parameters:
p- the target container- Returns:
- the y-axis alignment preference
-
putConstraint
public void putConstraint(String e1, Component c1, int pad, String e2, Component c2)
Links edgee1of componentc1to edgee2of componentc2, with a fixed distance between the edges. This constraint will cause the assignmentvalue(e1, c1) = value(e2, c2) + padto take place during all subsequent layout operations.- Parameters:
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 anchor- See Also:
putConstraint(String, Component, Spring, String, Component)
-
putConstraint
public void putConstraint(String e1, Component c1, Spring s, String e2, Component c2)
Links edgee1of componentc1to edgee2of componentc2. As edge(e2, c2)changes value, edge(e1, c1)will be calculated by taking the (spring) sum of(e2, c2)ands. Each edge must have one of the following values:SpringLayout.NORTH,SpringLayout.SOUTH,SpringLayout.EAST,SpringLayout.WEST,SpringLayout.VERTICAL_CENTER,SpringLayout.HORIZONTAL_CENTERorSpringLayout.BASELINE.- Parameters:
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 anchor- See Also:
putConstraint(String, Component, int, String, Component),NORTH,SOUTH,EAST,WEST,VERTICAL_CENTER,HORIZONTAL_CENTER,BASELINE
-
getConstraints
public SpringLayout.Constraints getConstraints(Component c)
Returns the constraints for the specified component. Note that, unlike theGridBagLayoutgetConstraintsmethod, 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.- Parameters:
c- the component whose constraints will be returned- Returns:
- the constraints for the specified component
-
getConstraint
public 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. This method, instead of returning the current binding for the edge, returns a proxy that tracks the characteristics of the edge even if the edge is subsequently rebound. Proxies are intended to be used in builder environments where it is useful to allow the user to define the constraints for a layout in any order. Proxies do, however, provide the means to create cyclic dependencies amongst the constraints of a layout. Such cycles are detected internally bySpringLayoutso that the layout operation always terminates.- Parameters:
edgeName- must be one ofSpringLayout.NORTH,SpringLayout.SOUTH,SpringLayout.EAST,SpringLayout.WEST,SpringLayout.VERTICAL_CENTER,SpringLayout.HORIZONTAL_CENTERorSpringLayout.BASELINEc- the component whose edge spring is desired- Returns:
- a proxy for the spring controlling the distance between the specified edge and the top or left edge of its parent
- See Also:
NORTH,SOUTH,EAST,WEST,VERTICAL_CENTER,HORIZONTAL_CENTER,BASELINE
-
-