GUI Components: Part 2 - Java: How to Program Early Objects - page 943

the components into rows and columns. The initial row and column numbers should be
0, so that the GridBagLayout layout manager can use the row and column numbers to
properly place the components in the grid. Figure 22.18 demonstrates drawing the lines
for the rows and columns over a GUI.

Column

0 1 2

0
1
2
3

Row

Fig. 22.18 | Designing a GUI that will use GridBagLayout .

GridBagConstraints
A GridBagConstraints object describes how a component is placed in a GridBagLayout .
Several GridBagConstraints fields are summarized in Fig. 22.19.

Field Description

Specifies the relative position ( NORTH , NORTHEAST , EAST , SOUTHEAST , SOUTH ,
SOUTHWEST , WEST , NORTHWEST , CENTER ) of the component in an area that it
does not fill.

anchor

Resizes the component in the specified direction ( NONE , HORIZONTAL , VER-
TICAL , BOTH ) when the display area is larger than the component.

fill

The column in which the component will be placed. gridx

The row in which the component will be placed.

gridy

The number of columns the component occupies.

gridwidth

The number of rows the component occupies.

gridheight

The amount of extra space to allocate horizontally. The grid slot can
become wider when extra space is available.

weightx

The amount of extra space to allocate vertically. The grid slot can become
taller when extra space is available.

weighty

Fig. 22.19 | GridBagConstraints fields.

GridBagConstraints Field anchor
GridBagConstraints field anchor specifies the relative position of the component in an
area that it does not fill. The variable anchor is assigned one of the following GridBagCon-
straints constants: NORTH , NORTHEAST , EAST , SOUTHEAST , SOUTH , SOUTHWEST , WEST ,
NORTHWEST or CENTER . The default value is CENTER .