Swing Hacks

172

|

Chapter 4, File Choosers

#32 Preview ZIP and JAR Files

HACK

Just like ZipEntryFileProxy, ZipFileProxy wraps a real file object and passes

most method invocations to the superclass. The special code here is in

parse( ), which loops through each entry in the ZIP file, breaks each path-

name into its constituent parts, and builds up a set of nested

HashTables.

Each directory entry is represented by a

HashMap of child filenames. A master

map holds the directory entries. This nested structure is what lets the

ZipEntryFileProxy find its place in the virtual tree of files.

Build a Custom Filesystem View

Now that you have a tree of virtual File objects, you can implement the real

FileSystemView. As shown in Example 4-3, ZipFileSystemView overrides each

of its parent class’s methods, redirecting them to ZIP-specific code if the file

is an instance of a

ZipEntryFileProxy.

String node_name = name;

if(brk != -1) {

node_name = full_name.substring(brk+1);

}

if(ze.isDirectory( )) {

HashMap children = new HashMap( );

hash.put(full_name,children);

}

Map parent_children = (Map)hash.get(parent);

parent_children.put(full_name,"");

}

}

}

Example 4-3. ZipFileSystemView class

public class ZipFileSystemView extends FileSystemView {

public ZipFileSystemView( ) throws IOException { }

public File createNewFolder(File file) { return null; }

public File createFileObject(File dir, String filename) {

if(dir instanceof ZipEntryFileProxy) ...