The Java TM Tutorial

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Trail: Creating a GUI with JFC/Swing
Lesson: Converting to Swing

## General Conversion Tips

> This section gives you conversion tips for dealing with empty space, painting, and images.

### Empty Space

> If you use the Java Look & Feel, your Swing program might have less space between components than the previous version. If you want to add more space, you can do it using any combination of layout managers, empty borders, and invisible spacer components. See Putting Space Between Components for more information. You can also use the `setMargin` method for text components.

### Converting Painting Code

> AWT components perform painting in the `paint` and `update` methods. Swing components use the `paintComponent` method instead. To take advantage of automatic background painting, your implementation of `paintComponent` should call `super.paintComponent`, first thing. See Overview of Custom Painting for details.

> Note that Swing components automatically use double buffering to make their painting smooth. If the program that you're converting implements double buffering explicitly, this is a unique opportunity to delete some code! For example the AWT-based animation program `ImageSequence.java` paints to an off-screen image and then paints the image to the screen all at once. Its Swing counterpart, `ImageSequenceTimer.java`, simply puts its paint code in the custom component's `paintComponent` method, and double buffering is handled automatically. During the conversion process, we removed `offImage`, `offGraphics`, and all code that referred to them.

> If your painting code puts a title or edges around the component, consider replacing it with a border. For example, you can easily create a box around a group of components by adding the components to a `JPanel` and making the panel have a border. The AWT-based program `CoordinatesDemo` uses a class called `FramedArea` that exists solely to put a frame around the coordinate area. The Swing version of this program, `CoordinatesDemo`, uses a border instead and deletes the `FramedArea` class.

### Converting Images

> Although you can use `Image` objects in Swing programs, you might want to convert some or all of them into `Icon` objects. The main reason is Swing components that can display images -- labels, buttons, cell renderers in tables and trees and lists, tabbed panes, menus, and so on -- do so using `Icon` objects. Another reason is that `Icon` objects have accessibility support built in.

> You can convert an `Image` into an icon in one of two ways. The first way is to use `new ImageIcon(anImage)`. The second is to create an `ImageIcon` using the same data source that you used to create the `Image`. When you use the second way, the constructor automatically loads the image data, returning when the image is ready to use.

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