Open File Dialog in Android

For my app-in-progress, I needed to allow the user to select a file from their Android system that my app can use. I was surprised to learn there is no real built-in file chooser dialog. From my experience with .NET and the Win32 API, that's a function that you can count on being there. I did not think it would be difficult to write one myself, but I'm always looking for quicker ways to get there.

Eventually, I found a blog post by Android-er, who shows a very simple version of the mechanics behind a file open dialog. After getting my version of his code up and running, I wanted to make a few modifications to meet my needs. These modifications are:

• Alphabetize the list of files
• Exclude hidden files, hidden directories, and directories without read access
• Only show files with compatible file extensions

Fortunately, this was very easy to do using standard Java API's. Instead of calling:

File[] files = f.listFiles();

I create a FileFilter to filter out the results:

File[] files = f.listFiles(new FileFilter() {

@Override

public boolean accept(File pathname)

{

//If a file or directory is hidden, or unreadable, don't show it in the list.

if(pathname.isHidden())

return false;

if(!pathname.canRead())

return false;

//Show all directories in the list.

if(pathname.isDirectory())

return true;

//Check if there is a supported file type that we can read.

String fileName = pathname.getName();

String fileExtension;

int mid= fileName.lastIndexOf(".");

fileExtension = fileName.substring(mid+1,fileName.length());

for(String s : supportedFileExtensions) {

if(s.contentEquals(fileExtension)) {

return true;

}

}

return false;

}

});

The last change was to sort the files and directories alphabetically. I do the sorting operations after the list is constructed, but before the ArrayAdapter is initialized.

//Sort the files alphabetically.

Collections.sort(fileStringList);

Collections.sort(pathStringList);

fileListAdapter = new ArrayAdapter(this.getContext(), R.layout.open_file_entry, R.id.fileName, fileStringList);

ListView lv = (ListView) this.findViewById(R.id.pcap_files_list);

if(lv != null)

{

lv.setAdapter(fileListAdapter);

}

So far, this code is working as intended. I don't know if this is the most-optimal to do this, but that will be analyzed before I release this app to the market. For now, I'm still building out the basic infrastructure.