Understanding Layout Managers - Java SE 6

will honor these requests if at all possible, while maintaining the integrity of the layout

policy. You may override these methods for controls that you subclass. Default values are

provided otherwise.

Java has several predefined LayoutManager classes, several of which are described

next. You can use the layout manager that best fits your application.

FlowLayout

FlowLayout is the default layout manager. This is the layout manager that the preceding

examples have used. FlowLayout implements a simple layout style, which is similar to

how words flow in a text editor. The direction of the layout is governed by the container 's

component orientation property, which, by default, is left to right, top to bottom. Therefore,

by default, components are laid out line-by-line beginning at the upper-left corner. In all

cases, when a line is filled, layout advances to the next line. A small space is left between

each component, above and below, as well as left and right. Here are the constructors for

FlowLayout:

FlowLayout( )

FlowLayout(int how)

FlowLayout(int how, int horz, int vert)

The first form creates the default layout, which centers components and leaves five pixels of

space between each component. The second form lets you specify how each line is aligned.

Valid values for how are as follows:

FlowLayout.LEFT

FlowLayout.CENTER

FlowLayout.RIGHT

FlowLayout.LEADING

FlowLayout.TRAILING

These values specify left, center, right, leading edge, and trailing edge alignment, respectively.

The third constructor allows you to specify the horizontal and vertical space left between

components in horz and vert, respectively.

Here is a version of the CheckboxDemo applet shown earlier in this chapter, modified

so that it uses left-aligned flow layout:

// Use left-aligned flow layout.

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

</applet>

public class FlowLayoutDemo extends Applet

implements ItemListener {

String msg = "";

Checkbox winXP, winVista, solaris, mac;

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