Creating Windows - Beginning Java 2 SDK - page 697

With the constraints for the buttons as before, the
window will look like:
Both the Push and the Press button occupy the same space in the container, but, because fill is set to
NONE , they are not expanded to fill the space in either direction. The ipadx and ipady constraints
specify by how much the buttons are to be expanded from their preferred size - by thirty pixels on the
left and right, and ten pixels on the top and bottom. The overall arrangement remains the same.
You need to experiment with using GridBagLayout and GridBagConstraints to get a good feel
for how the layout manager works because you are likely to find yourself using it quite often.
Using a SpringLayout Manager
You can set the layout manager for the content pane of a JFrame object, aWindow , to be a
SpringLayout manager like this:
SpringLayout layout = new SpringLayout(); // Create a layout manager
Container content = aWindow.getContentPane(); // Get the content pane
content.setLayout(layout);
The layout manager defined by the SpringLayout class determines the position and size of each
component in the container according to a set of constraints that are defined by Spring objects. Every
component within a container using a SpringLayout manager has an object associated with it of type
SpringLayout.constraints that can define constraints on the position of each of the four edges of
the component. Before you can access the SpringLayout.constraints object for an object, you
must first add the object to the container. For example:
JButton button = new JButton("Press Me");
content.add(button);
Now we can call the getConstraint() method for the SpringLayout object to obtain the object
encapsulating the constraints:
SpringLayout.Constraints buttonConstr = layout.getConstraints(button);
To constrain the location and size of the button object, we will call methods of the buttonConstr
object to set individual constraints.