Using Layout Managers

Laying Out Components within a Container

Using Layout Managers

Every container, by default, has a layout manager -- an object that implements the LayoutManager interface. If a container's default layout manager doesn't suit your needs, you can easily replace it with another one. The AWT supplies layout managers that range from the very simple (FlowLayout and GridLayout) to the special purpose (BorderLayout and CardLayout) to the very flexible (GridBagLayout and BoxLayout).
This section gives you an overview of the layout managers the AWT provides, gives you some general rules for using layout managers, and then tells you how to use each of the AWT layout managers. In these pages are applets illustrating layout management.
General Rules for Using Layout Managers

This section answers some common questions about layout managers:

How do you choose a layout manager?
How do you create a layout manager, associate it with a container, and tell it to start working?
How does the layout manager know what components it manages?

How to Use BorderLayout

BorderLayout is the default layout manager for all Window objects, such as JFrames and JOptionPanes. It uses five areas to hold components: north, south, east, west, and center. All extra space is placed in the center area. Here's an applet that puts one button in each area.

Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:

Note: Because the preceding applet runs using Java Plug-in 1.1.1, it is a Swing 1.0.3 version of the applet. To run the Swing 1.1 Beta 3 version of the applet, you can use the JDK Applet Viewer to view Border.html, specifying swing.jar in the Applet Viewer's class path. For more information about running applets, refer to About Our Examples.

How to Use CardLayout

Use the CardLayout class when you have an area that can contain different components at different times. A CardLayout is often controlled by a JComboBox, with the state of the JComboBox determining which JPanel (group of components) the CardLayout displays. Here's an applet that uses a JComboBox and CardLayout in this way.

Your browser can't run 1.0 Java applets, so here are pictures of the window the program brings up:

Note: Because the preceding applet runs using Java Plug-in 1.1.1, it is a Swing 1.0.3 version of the applet. To run the Swing 1.1 Beta 3 version of the applet, you can use the JDK Applet Viewer to view Card.html, specifying swing.jar in the Applet Viewer's class path. For more information about running applets, refer to About Our Examples.

How to Use FlowLayout

FlowLayout is the default layout manager for event JPanel. It simply lays out components from left to right, starting new rows if necessary. Both panels in the CardLayout applet above use FlowLayout. Here's another example of an applet that uses a FlowLayout.

Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:

Note: Because the preceding applet runs using Java Plug-in 1.1.1, it is a Swing 1.0.3 version of the applet. To run the Swing 1.1 Beta 3 version of the applet, you can use the JDK Applet Viewer to view Flow.html, specifying swing.jar in the Applet Viewer's class path. For more information about running applets, refer to About Our Examples.

How to Use GridLayout

GridLayout simply makes a bunch of components equal in size and displays them in the requested number of rows and columns. Here's an applet that uses a GridLayout to control the display of five buttons.

Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:

Note: Because the preceding applet runs using Java Plug-in 1.1.1, it is a Swing 1.0.3 version of the applet. To run the Swing 1.1 Beta 3 version of the applet, you can use the JDK Applet Viewer to view Grid.html, specifying swing.jar in the Applet Viewer's class path. For more information about running applets, refer to About Our Examples.

How to Use GridBagLayout

GridBagLayout is the most sophisticated, flexible layout manager the AWT provides. It aligns components by placing them within a grid of cells, allowing some components to span more than one cell. The rows in the grid aren't necessarily all the same height; similarly, grid columns can have different widths. Here's an applet that uses a GridBagLayout to manage ten buttons in a panel.

Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:

Note: Because the preceding applet runs using Java Plug-in 1.1.1, it is a Swing 1.0.3 version of the applet. To run the Swing 1.1 Beta 3 version of the applet, you can use the JDK Applet Viewer to view GridBag.html, specifying swing.jar in the Applet Viewer's class path. For more information about running applets, refer to About Our Examples.

How to Use BoxLayout

Note: The box layout page is currently in the lesson about using the Swing components. Eventually, it will be moved here.]

Laying Out Components within a Container