Module java.desktop
Package 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): 

               EAST = WEST + WIDTH
              SOUTH = NORTH + HEIGHT
  HORIZONTAL_CENTER = WEST + WIDTH/2
    VERTICAL_CENTER = NORTH + HEIGHT/2
  ABSOLUTE_BASELINE = NORTH + RELATIVE_BASELINE*

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.

[RELATIVE_BASELINE is a private constraint that is set automatically when the SpringLayout.Constraints(Component) constructor is called or when a constraints object is registered with a SpringLayout object.]

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.

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.

Since:
1.4

  • Constructor Summary

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

    Modifier and Type
    Method
    Description
    Spring
    getConstraint(String edgeName)
    Returns the value of the specified edge, which may be a derived value, or even null.
    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 declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Constraints

      public Constraints()
      Creates an empty Constraints object.

    • Constraints

      public 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

    • Constraints

      public 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

    • Constraints

      public 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

  • Method Details