Recipe 23.5. Filtering Files That Display in the Browser Window

Problem

You want to filter the type of files that display in the browse dialog box so the user only sees the types of files you want to allow her to upload.

Solution

Pass an array of FileFilter objects to the browse( ) method.

Discussion

By default the browse( ) method displays a dialog box that displays all files on the user's filesystem. However, you also have the option of filtering the types of files that are displayed. For example, you may want to display only image files or only text files. You can accomplish this by passing an array of flash.net.FileFilter objects to the browse( ) method.

The FileFilter constructor requires at least two parameters:

• The first parameter determines what displays in the "Files of type" drop-down menu in the browse dialog box.

• The second parameter determines which file extensions are filtered.

File extensions must be semicolon-delimited, each prepended with an asterisk and a dot. The following constructs a FileFilter object that filters for files with file extensions of .png, .gif, and .jpg:

var fileFilter:FileFilter = new FileFilter("Images", "*.png;*.gif;*.jpg");

Additionally, you may opt to specify a third parameter of Macintosh file types. As with file extensions, file types are semicolon delimited. When the Macintosh file types parameter is omitted, the file extensions are used as a filter for both Windows and Macintosh files. When the Macintosh file types parameter is specified, the file extensions are used as a filter for Windows files, while they are ignored for Macintosh files in preference of the Macintosh file types. Macintosh operating systems now support file extensions as a way of determining the file type, yet they also continue to support type codes assigned to the files.

You can specify which filter (or filters) to use by passing them as elements of an array to the browse( ) method, as follows:

fileReference.browse([fileFilter]);

In the preceding example, only one filter is passed to the browse( ) method. Each filter that's passed to the browse( ) method adds a new option to the "Files of type" drop-down menu in the browse dialog box. For example, the following code allows four options in the Files of type menuImages, Documents, Archives, and All.

var fileFilter1:FileFilter = new FileFilter("Images", "*.png;*.gif;*.jpg"); var fileFilter2:FileFilter = new FileFilter("Documents", "*.txt;*.doc;*.pdf;*.rtf"); var fileFilter3:FileFilter = new FileFilter("Archives", "*.zip;*.tar;*.hqx"); var fileFilter4:FileFilter = new FileFilter("All", "*.*"); _fileReference.browse([fileFilter1, fileFilter2, fileFilter3, fileFilter4]);

When you pass an array of FileFilter objects to the browse( ) method, there is a possibility that the browse( ) method can throw an argument error of type ArgumentError. Argument errors occur if any of the FileFilter objects have incorrectly formatted values.

The file filter parameter also works with the browse( ) method of FileReferenceList.

See Also

Recipe 23.4