How to recursively scan directories in Android

Question

How can I recursively scan directories in Android and display file name(s)? I'm trying to scan, but it's slow (force close or wait). I'm using the FileWalker class given in a separate answer to this question.

Answer 1

You should almost always access the file system only from a non-UI thread. Otherwise you risk blocking the UI thread for long periods and getting an ANR. Run the FileWalker in an AsyncTask's doInBackground().

This is a slightly optimized version of FileWalker:

public class Filewalker {

    public void walk(File root) {

        File[] list = root.listFiles();

        for (File f : list) {
            if (f.isDirectory()) {
                Log.d("", "Dir: " + f.getAbsoluteFile());
                walk(f);
            }
            else {
                Log.d("", "File: " + f.getAbsoluteFile());
            }
        }
    }   
}

You can invoke it from a background thread like this:

Filewalker fw = new Filewalker();
fw.walk(context.getFilesDir());

Answer 2

System.out.println calls are really slow (well it's not really the function itself, but the underlying PrintStream which takes a lot of time to write text in the console).

Replace them by something else and it should be fine. For example, you can create and return an array with the file names.