Swing Hacks

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Chapter 4, File Choosers

#32 Preview ZIP and JAR Files

HACK

Note the isTraversable( ) method, which returns true if the file ends with

.zip or is an instance of

ZipEntryFileProxy. Without this, the JFileChooser

would never let the user navigate inside of ZIP files.

Put It All Together

The class in Example 4-4 creates a JFileChooser with a ZipFileSystemView.

The only custom code beyond the view itself is a check to see if the selected

file is a

ZipEntryFileProxy. If so, the program will cast the file to a

ZipEntryFileProxy and call getInputStream( ). If not, it will just create a

FileInputStream

as normal.

As you can see, this method of extending the

JFileChooser to support an

alternative filesystem is quite hackish. Sadly, it’s the only way to do such a

thing without writing a completely custom file chooser. This is probably

why so many IDE authors have just chucked the entire

JFileChooser and

FileSystemView API in favor of a custom dialog. However, if you wish to

remain within the standard API, you can certainly do it, as this hack proves.

As a future enhancement, you might make this class more generic, handling

the nasty details of file wrapping while delegating the actual alternative file-

system to a subclass. This would create an API more like

TreeModel, from

which other developers can create their own implementations easily.

Example 4-4. A sample program

public class ZipTest {

public static void ...