javax.swing
Class SpringLayout.Constraints

java.lang.Object
  javax.swing.SpringLayout.Constraints

Enclosing class:

SpringLayout

public static class SpringLayout.Constraints
extends Object

A Constraints object holds the constraints that govern the way a component's size and position change in a container controlled by a SpringLayout. A Constraints object is like a Rectangle, in that it has x, y, width, and height properties. In the Constraints object, however, these properties have Spring values instead of integers. In addition, a Constraints object can be manipulated as four edges -- north, south, east, and west -- using the constraint property.

The following formulas are always true for a Constraints object (here WEST and x are synonyms, as are and NORTH and y): object:

 EAST = WEST + WIDTH
 SOUTH = NORTH + HEIGHT
 HORIZONTAL_CENTER = WEST + WIDTH/2
 VERTICAL_CENTER = NORTH + HEIGHT/2
 ABSOLUTE_BASELINE = NORTH + RELATIVE_BASELINE*
 
 west = x
 north = y
 east = x + width
 south = y + height 

Note

For example, if you have specified the WIDTH and WEST (X) location the EAST is calculated as WEST + WIDTH. If you instead specified the WIDTH and EAST locations the WEST (X) location is then calculated as EAST - WIDTH. Because a Constraints object's properties -- representing its edges, size, and location -- can all be set independently and yet are interrelated, the object can become over-constrained. For example, if both the x and width properties are set and then the east edge is set, the object is over-constrained horizontally. When this happens, one of the values (in this case, the x property) automatically changes so that the formulas still hold.

[RELATIVE_BASELINE is a private constraint that is set automatically when the SpringLayout.Constraints(Component) constuctor is called or when a constraints object is registered with a SpringLayout object.] The following table shows which value changes when a Constraints object is over-constrained horizontally.

Note : In this document, operators represent methods in the Spring class. For example, "a + b" is equal to Spring.sum(a, b), and "a - b" is equal to Spring.sum(a, Spring.minus(b)). See the Spring API documentation for further details of spring arithmetic.

Value Being Set (method used)	Result When Over-Constrained Horizontally (x, width, and the east edge are all non-null)
x or the west edge (setX or setConstraint)	width value is automatically set to east - x.
width (setWidth)	east edge's value is automatically set to x + width.
east edge (setConstraint)	x value is automatically set to east - width.

Because a Constraints object's properties -- representing its edges, size, and location -- can all be set independently and yet are interrelated, a Constraints object can become over-constrained. For example, if the WEST, WIDTH and EAST edges are all set, steps must be taken to ensure that the first of the formulas above holds. To do this, the Constraints object throws away the least recently set constraint so as to make the formulas hold. The rules for the vertical properties are similar:

Value Being Set (method used)	Result When Over-Constrained Vertically (y, height, and the south edge are all non-null)
y or the north edge (setY or setConstraint)	height value is automatically set to south - y.
height (setHeight)	south edge's value is automatically set to y + height.
south edge (setConstraint)	y value is automatically set to south - height.

Constructor Summary
SpringLayout.Constraints ()           Creates an empty Constraints object.
SpringLayout.Constraints ( Component  c)           Creates a Constraints object with suitable x, y, width and height springs for component, c.
SpringLayout.Constraints ( Spring  x, Spring  y)           Creates a Constraints object with the specified values for its x and y properties.
SpringLayout.Constraints ( Spring  x, Spring  y, Spring  width, Spring  height)           Creates a Constraints object with the specified values for its x, y, width, and height properties.

 

Method Summary
Spring	getConstraint ( String           Returns the value of the specified edge, which may be a derived value, or even null. edge.
Spring	getHeight ()           Returns the value of the height property.
Spring	getWidth ()           Returns the value of the width property.
Spring	getX ()           Returns the value of the x property.
Spring	getY ()           Returns the value of the y property.
void	setConstraint ( String  edgeName, Spring  s)           Sets the spring controlling the specified edge.
void	setHeight ( Spring  height)           Sets the height property, which controls the height of a component.
void	setWidth ( Spring  width)           Sets the width property, which controls the width of a component.
void	setX ( Spring  x)           Sets the x property, which controls the x value of a component's location.
void	setY ( Spring  y)           Sets the y property, which controls the y value of a component's location.

 

Methods inherited from class java.lang. Object
clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait

 

Constructor Detail

SpringLayout.Constraints

public SpringLayout.Constraints()

Creates an empty Constraints object.

SpringLayout.Constraints

public SpringLayout.Constraints(Spring x,
                                Spring y)

Creates a Constraints object with the specified values for its x and y properties. The height and width springs have null values.

Parameters:

x - the spring controlling the component's x value

y - the spring controlling the component's y value

SpringLayout.Constraints

public SpringLayout.Constraints(Spring x,
                                Spring y,
                                Spring width,
                                Spring height)

Creates a Constraints object with the specified values for its x, y, width, and height properties. Note: If the SpringLayout class encounters null values in the Constraints object of a given component, it replaces them with suitable defaults.

Parameters:

x - the spring value for the x property

y - the spring value for the y property

width - the spring value for the width property

height - the spring value for the height property

SpringLayout.Constraints

public SpringLayout.Constraints(Component c)

Creates a Constraints object with suitable x, y, width and height springs for component, c. The x and y springs are constant springs initialised with the component's location at the time this method is called. The width and height springs are special springs, created by the Spring.width() and Spring.height() methods, which track the size characteristics of the component when they change.

Parameters:

c - the component whose characteristics will be reflected by this Constraints object

Throws:

NullPointerException - if c is null.

Since:

1.5

setX

public void setX(Spring x)

Sets the x property, which controls the x value of a component's location.

Parameters:

x - the spring controlling the x value of a component's location

See Also:

getX() , SpringLayout.Constraints

getX

public Spring getX()

Returns the value of the x property.

Returns:

the spring controlling the x value of a component's location

See Also:

setX(javax.swing.Spring) , SpringLayout.Constraints

setY

public void setY(Spring y)

Sets the y property, which controls the y value of a component's location.

Parameters:

y - the spring controlling the y value of a component's location

See Also:

getY() , SpringLayout.Constraints

getY

public Spring getY()

Returns the value of the y property.

Returns:

the spring controlling the y value of a component's location

See Also:

setY(javax.swing.Spring) , SpringLayout.Constraints

setWidth

public void setWidth(Spring width)

Sets the width property, which controls the width of a component.

Parameters:

width - the spring controlling the width of this Constraints object

See Also:

getWidth() , SpringLayout.Constraints

getWidth

public Spring getWidth()

Returns the value of the width property.

Returns:

the spring controlling the width of a component

See Also:

setWidth(javax.swing.Spring) , SpringLayout.Constraints

setHeight

public void setHeight(Spring height)

Sets the height property, which controls the height of a component.

Parameters:

height - the spring controlling the height of this Constraints object

See Also:

getHeight() , SpringLayout.Constraints

getHeight

public Spring getHeight()

Returns the value of the height property.

Returns:

the spring controlling the height of a component

See Also:

setHeight(javax.swing.Spring) , SpringLayout.Constraints

setConstraint

public void setConstraint(String edgeName,
                          Spring s)

Sets the spring controlling the specified edge. The edge must have one of the following values: SpringLayout.NORTH, SpringLayout.SOUTH, SpringLayout.EAST, SpringLayout.WEST, SpringLayout.HORIZONTAL_CENTER, SpringLayout.VERTICAL_CENTER, SpringLayout.BASELINE, SpringLayout.WIDTH or SpringLayout.HEIGHT. For any other String value passed as the edge, no action is taken. For a null edge, a NullPointerException is thrown. The edge must have one of the following values: SpringLayout.NORTH, SpringLayout.SOUTH, SpringLayout.EAST, SpringLayout.WEST.

Parameters:

edgeName - the edge to be set

s - the spring controlling the specified edge

Throws:

NullPointerException - if edgeName is null

See Also:

getConstraint(java.lang.String) , SpringLayout.NORTH , SpringLayout.SOUTH , SpringLayout.EAST , SpringLayout.WEST , SpringLayout.HORIZONTAL_CENTER , SpringLayout.VERTICAL_CENTER , SpringLayout.BASELINE , SpringLayout.WIDTH , SpringLayout.HEIGHT , SpringLayout.Constraints

getConstraint

public Spring getConstraint(String edgeName)

Returns the value of the specified edge, which may be a derived value, or even null. The edge must have one of the following values: SpringLayout.NORTH, SpringLayout.SOUTH, SpringLayout.EAST, SpringLayout.WEST, SpringLayout.HORIZONTAL_CENTER, SpringLayout.VERTICAL_CENTER, SpringLayout.BASELINE, SpringLayout.WIDTH or SpringLayout.HEIGHT. For any other String value passed as the edge, null will be returned. Throws NullPointerException for a null edge. Returns the value of the specified edge. The edge must have one of the following values: SpringLayout.NORTH, SpringLayout.SOUTH, SpringLayout.EAST, SpringLayout.WEST.

Parameters:

edgeName - the edge whose value is to be returned

Returns:

the spring controlling the specified edge, may be null edge

Throws:

NullPointerException - if edgeName is null

See Also:

setConstraint(java.lang.String, javax.swing.Spring) , SpringLayout.NORTH , SpringLayout.SOUTH , SpringLayout.EAST , SpringLayout.WEST , SpringLayout.HORIZONTAL_CENTER , SpringLayout.VERTICAL_CENTER , SpringLayout.BASELINE , SpringLayout.WIDTH , SpringLayout.HEIGHT , SpringLayout.Constraints