Swing I - Absolute Java - page 967

Note that if we had used the FlowLayout manager, as in the preceding code, then the
add method would have only one argument. With a FlowLayout manager, the items
are displayed in the order they are added, so that the labels above would be displayed
all on one line as follows:

First label Second label Third label
The full program is in the files FlowLayoutJFrame.java and FlowLayoutDemo.java
on the accompanying website. You will see a number of examples of GUIs that use the
FlowLayout manager class later in this chapter.

extra code
on website

Grid Layout Managers
A GridLayout manager arranges components in a two-dimensional grid with some
number of rows and columns. With a GridLayout manager, each entry is the same
size. For example, the following says to use a GridLayout manager with aContainer ,
which can be a JFrame or other container:

GridLayout

aContainer.setLayout( new GridLayout(2, 3));
The two numbers given as arguments to the constructor GridLayout specify the
number of rows and columns. This would produce the following sort of layout:

The lines will not be visible unless you do something special to make them so. They are
just included here to show you the region boundaries.
When using a GridLayout manager, each component is stretched so that it
completely fills its grid position.
Although you specify a number of rows and columns, the rules for the number of
rows and columns is more complicated than what we have said so far. If the values for
the number of rows and the number of columns are both nonzero, then the number of
columns will be ignored. For example, if the specification is new GridLayout(2, 3) ,
then some sample sizes are as follows: If you add six items, the grid will be as shown. If
you add seven or eight items, a fourth column is automatically added, and so forth. If you
add fewer than six components, there will be two rows and a reduced number of columns.
There is another way to specify that the number of columns is to be ignored. You
can do this by setting the number of columns to zero, which will allow any number of
columns. So a specification of (2, 0) is equivalent to (2, 3) , and in fact is equivalent to
(2, n) for any nonnegative value of n . Similarly, you can specify that the number of rows is
to be ignored by setting the number of rows to zero, which will allow any number of rows.
When using the GridLayout class, the method add has only one argument. The items
are placed in the grid from left to right, first filling the top row, then the second row, and
so forth. You are not allowed to skip any grid position (although you will later see that you
can add something that does not show and so gives the illusion of skipping a grid position).
A sample use of the GridLayout class is given in Display 17.9 .