Frames, panels and layouts - An Introduction to Graphical User Interfaces with Java Swing - page 20

Figure 2.6 Output of LayoutDriver . Standard flow layout; flow layout with bigger spac-
ing; grid layout

row number is adjusted depending on the number of embedded components. In
program LayoutFrame we generate a 2 × 4 grid for five components. The layout

manager then generates a 2 3 grid, where only one cell is empty. Sometimes

one embeds dummy components into a grid layout. These are Swing components,
usually labels, with no function other than to fill certain cells. They can be used to
produce an 'empty' cell between two other cells. Chapter 6 contains an example.
The dimensions of the embedded components are basically ignored by the grid
layout; the components completely fill the cells. See also Figure 2.5c.

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Below we list the constructor and some methods for grid layouts. The number
of rows r and columns c and also the width of the gaps can be passed between the
columns ( hdist ) and rows ( vdist ):

GridLayout( int r, int c);
setHgap( int hdist);
setVgap( int vdist);
The following listings LayoutFrame and LayoutDriver show examples for the
layouts. The first defines a frame for which the layout can be selected by passing
a LayoutManager in the constructor.
Program LayoutDriver generates three LayoutFrame s and makes them visible.
The first one is given a standard flow layout. The second one receives a flow
layout with specified distances between rows/columns and left alignment. The
third frame is given a 2

4 grid layout. The locations in the showIt instructions
are set in such a way that the three frames appear side by side. Figure 2.6 shows
the result.

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File: its/Layouts/LayoutFrame.java

1. package its.Layouts;
2.
3. import java.awt.LayoutManager;
4. import its.SimpleFrameWithPanels.ColorPanel;
5. import java.awt.Color;
6. import its.SimpleFrame.*;
7.