Question

I’m trying to list all folders in sdcard via ListAdapter. But I’m getting runtime exceptions @ item.add(file.getName() + "/");. Is there a better way to convert File[] to List<String>?

private List <String>        item    = null;

String extState = Environment.getExternalStorageState();
if (!extState.equals(Environment.MEDIA_MOUNTED)) {
    ....
} else {
    File sd = Environment.getExternalStorageDirectory();
    FileFilter filterDirectoriesOnly = new FileFilter() {
        public boolean accept(File file) {
            return file.isDirectory();
        }
    };
    File[] sdDirectories = sd.listFiles(filterDirectoriesOnly);
    for (int i = 0; i < sdDirectories.length; i++) {
        File file = sdDirectories[i];
        item.add(file.getName() + "/");
    }
    ArrayAdapter <String> fileList = new ArrayAdapter <String>(this, R.layout.row, item);
    setListAdapter(fileList);
}

Answer 1

You can make it a little shorter by using an enhanced for loop:

File[] sdDirectories = sd.listFiles(filterDirectoriesOnly);
for (File file : sdDirectories)
{
    item.add(file.getName() + "/");
}

There’s a method to get file names directly, but they won’t have your trailing /, and you have to be able to filter by file name:

String[] fileNames = sd.list(fileNameFilter);
List<String> fileNamesList = Arrays.asList(fileNames);