Layout : Java Glossary

Components in the Layout

• Component. getMinimumSize() — smallest could be shrunk to.
• Component. getMaximumSize() — largest it makes sense to grow it to.
• Component. getPreferredSize() — ideal size.
• Component. getSize() — actual size it is now.

These methods often return 0,0 as the size. The reason is, they rely on the underlying GUI to compute the size, and if there in no peer object yet, there is no hook to ask the native GUI. See addNotify.

What Layout Managers Do

• layoutContainer( Container c )

• preferredLayoutSize( Container c )
• maximumLayoutSize( Container c )
• minimumLayoutSize( Container c )

Null Layouts

You should almost never use null layouts and setLocation. This is a last ditch emergency method when all layout managers have failed to give you decent positioning and it would be impossible to write a layout manager with enough common sense.

When you do use manual layout you must do several things:

• Container.setLayout ( null ) or JFrame.getContentPane().setLayout ( null ).
• setLocation of every element in the container.
• setSize of every element in the container.
• Make sure you also set the size of the container and freeze the size of the container by implementing getPreferredSize, getMinimumSize and getMaximumSize, or in JDK 1.5+, use setPreferredSize, setMinimumSize and setMaximumSize.

Nested Containers

Table of Possible Layout Managers

Possible Layout Managers
Layout	Purpose
AbsoluteLayout	Netbeans absolute position layout.
BorderLayout	Place components on a simple north, south, east, west, center grid. Sun’s Javadoc on the BorderLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on BorderLayout
BoxLayout	Place components in a single row or column. Designed to work with glue and strut objects of the Box class to control where extra space goes. Aligns based on the Component.getAlignmentX and Component.getAlignmentY properties of the Components in the Container. To control alignment use Component.setAlignment( 0.0F ) for left aligned, setAlignmentX( .5F ) for centered and setAlignmentX( 1.0F ) for right aligned. Only available in Swing. Sun’s Javadoc on the BoxLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on BoxLayout
CardLayout	Allows you to flip through several panels, where only one is visible at a time. Sun’s Javadoc on the CardLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on CardLayout
DesignGridLayout	Uses canonical grids as described in Patrizia Nanni’s Human-Computer Interaction: Principles of Interface Design. Beware, the html docmument is over 2 MB long and has a blank first page.
EasyLayout	Stripped down GridBagLayout. Has just weights, and grid numbers.
ExplicitLayout	Allows non-rectangular layouts. By Zooki Technology.
FillLayout	SWT. lays out equal-sized widgets in a single row or column.
FlowLayout	Simple flow left to right, top to bottom stream of components. This is a very rough and ready, quick and dirty layout for prototypes. If you want fine control and professional looks, try another. Sun’s Javadoc on the FlowLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on FlowLayout
FormLayout	Karsten Lentzsch’s free, open source LayoutManager. Karsten is the Leonardo da Vinci of layout designers. His layouts get every last picky detail correct, including working with larger-than-expected fonts. Even if you don’t use his layouts, read what he has to say about GUI design. Version 1.2 is coming soon which has layout variables for meta design constants. Last revised: 2008-04-04 For example, 85dlu for all label column widths, 100dlu for the minimum table height, etc. See scalable layouts for a discussion of the problem of scaling layouts.
GridBagLayout	Sun’s mother of all layout managers. It is complicated and powerful. To cover it requires a separate entry. Place components on a rough n x m grid. Some components may take up multiple cells. Fine tuning of whitespace around each component and alignment of each component within its grid cell. Requires a lot of tweaking to make it look right. The cells are not necessarily the same size. They adjust to fit the components, based on various hints you give.
GridLayout	Layout components in a regular n × m grid. All cells are the same width and height. Sun’s Javadoc on the GridLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on GridLayout
GridLayout SWT	SWT. lays out widgets in a grid FormLayout
GroupLayout	Part of Netbeans/Matisse. It is not bundled with the JDK. It backs up the visual layout abilities of Matisse.
HIGLayout	Similar to TableLayout, by Daniel Michelik
JTabbedPane	JTabbedPane is a JComponent, not a LayoutManager, but it behaves much like a CardLayout with tabs.
JSplitPane	JSplitPane is a JComponent, not a Layout, but it behaves much like one with two panels and a moveable boundary between them.
LabeledGridBagLayout	Like a GridBagLayout that automatically labels fields with their corresponding field names. Requires use of smart components that know their field labels. Part of the com.mindprod.business package.
Matisse	A new NetBeans scheme for building layouts interactively with a backing set of layout managers. It is still in alpha test.
MigLayout	Free. Intended to be a universal layout manager for all possible applications. This is RedGrittyBrick’s favourite layout manager. Has tools for writing resolution-independent code.
Packer	A front end to the GridBagLayout using a fluent interface to cut down the number of postitional parameters. Not to be confused with PackerLayout.
PackerLayout	A Java version of the Tcl/Tk layout manager. Some of the GridBag pad/expand abilities.
RainLayout	Orders components according to a Comparator.
RiverLayout	It mimics how text is positioned in a text editor, where the words words flow from left to right. They are normally separated with spaces, but if you want them aligned in columns you can use tab stops. You can insert line breaks where needed and even paragraph breaks to separate sections of text.
RowLayout	SWT. lays out widgets in a row or rows, with fill, wrap, and spacing options.
SpringLayout	Uses a model of structs and springs to control the sizes and positions of boxes. Only available in Swing. Sun’s Javadoc on the SpringLayout class : available: on the web at java.sun.com in the current JDK 1.6.0_07 or in the old JDK 1.5.0_16 or in the beta JDK 1.6.0_10 on your local J: drive. Sun’s tutorial on SpringLayout
StarLayout	Arranges objects in star shaped patterns. You place components by giving the angle and radius from the centre of the container.
TableLayout	A simplified GridBagLayout. You explicitly control the relative sizes of each row and column. By Daniel Barbalace and the ClearThought TableLayout Project.
ToolBarLayout	designed for use as LayoutManager for tool bar’s dock container. Its usage is very simple — all you need to provide is a Point object as constraint.
XYLayout	Borland absolute position layout.

NetBeans and JBuilder have GUI layout builders. Radical is a stand-alone GUI Builder.

Gotchas

• Some layouts such as GridBagLayout will let you put two elements in the same cell, then alternate which one appears with setVisible. Others, such as BorderLayout allow only one commponent per cell. You must pull off the effect with remove and add.
• GridBagLayout cells sometimes shrivel up to nothing unless you do something to make them hold their size, e.g. assigning weight, using a HORIZONTAL fill constraint or using an ipadx.

Learning More