GRAPHICAL USER INTERFACE (GUI) AND OBJECT-ORIENTED DESIGN (OOD) - Java Programming: From Problem Analysis to Program Design - page 339

TABLE 6-2 Some Methods of the class Container

Method / Description

public void add(Object obj)
//Method to add an object to the pane.

public void setLayout(Object obj)
//Method to set the layout of the pane.

The class Container is contained in the package java.awt . To use this class in your
program, you need to include one of the following statements:

import java.awt.*;

or:

6

import java.awt.Container;
As noted earlier, the method setLayout is used to set the layout of the content pane,
pane . To set the layout of the container to a grid, you use the class GridLayout .
Consider the following statement:

pane.setLayout( new GridLayout(5, 2));
This statement creates an object belonging to the class GridLayout and assigns that
object as the layout of the content pane, pane , by invoking the setLayout method.
Moreover, this statement sets the layout of the content pane, pane , to five rows and two
columns. This allows you to add 10 components arranged in five rows and two columns.
Note that the GridLayout manager arranges GUI components in a matrix formation
with the number of rows and columns defined by the constructor and that the compo-
nents are placed left to right, starting with the first row. For example, in the statement
pane.setLayout( new GridLayout(5, 2)); , the expression new GridLayout(5, 2) ,
invokes the constructor of the class GridLayout and sets the number of rows to 5 and
the number of columns to 2. Also, in this chapter, we only discuss the GridLayout
manager; additional layout managers are discussed in Chapter 12. Layout managers allow
you to manage GUI components in a content pane.
If you do not specify a layout, Java uses a default layout. If you specify a layout, you must set
the layout before adding any components. Once the layout is set, you can use the method
add to add the components to the pane; this process is described in the next section.

JLabel
Now you will learn how to create labels and add them to the pane. We assume the
following statements:

Container pane = getContentPane();
pane.setLayout( new GridLayout(4, 1));