Creating Windows - Beginning Java 2 SDK - page 700

Container
Origin

Set by
and

setX()
setY()

Position xy

NORTH

XSpring

Component
wSpring

SOUTH

Set by

setWidth()
setHeight()

and

Container

Setting Constraints on a Component

To set the width and height of the component, you call the setWidth() and setHeight() methods
for its SpringLayout.Constraints object:

Spring wSpring = Spring.constant(30,50,70); // Spring we'll use for width
Spring hSpring = Spring.constant(15); // Strut we'll use for height
buttonConstr.setWidth(wSpring); // Set component width constraint
buttonConstr.setHeight(hSpring); // Set component height constraint

The width constraint is applied between the WEST and EAST edges and the height constraint applies
between the component's NORTH and SOUTH edges. Since we have specified a strut for the height, there
is no leeway on this constraint; its value is fixed at 15.

If you want to explicitly set an edge constraint for a component, you call the setConstraint()
method for the component's SpringLayout.Constraints object:

layout.getConstraints(newButton)
.setConstraint(StringLayout.EAST, Spring.sum(xSpring, wSpring));

This statement ties the EAST edge of the newButton component to the WEST edge of the container by
a Spring object that is the sum of xSpring and wSpring .

You can also set constraints between pairs of vertical or horizontal edges where one edge can belong to a
different component from the other. For instance, we could add another button to the container like this:

JButton newButton = new JButton("Push");
content.add(newButton);

We can now constrain its WEST and NORTH edges by tying the edges to the EAST and SOUTH edges of
button. We use the putConstraint() method for the SpringLayout object to do this: