CODEWITHSUNDEEP
javaandroidfile
Binoy Babu
Binoy Babu

Reputation: 17119

A better way to convert `File[]` to `List<String>`

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);
}

Upvotes: 0

Views: 6466

Answers (3)

Brendan Long
Brendan Long

Reputation: 54242

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);

Upvotes: 1

ngesh
ngesh

Reputation: 13501

You are getting runtime Exception bacause

private List item = null;

is never initialised..

so first initialise then add..

What ever you are doing seems just right.. except that initialization..

Upvotes: 1

Rohan Prabhu
Rohan Prabhu

Reputation: 7302

Initialize your list (hence the Exception). But apart from that, looks pretty much alright to me. I mean, it is atleast what I would do. The only thing I would recommend here is that you don't re-instantiate the variables File sd and FileFilter filterdirectoriesOnly within the function, because I assume you would be calling it again and again as the user clicks on a directory and then loads results for a new directory. So the two objects I mentioned are the same but being re-initialised every time you make a call. You could just move it outside.

Upvotes: 0

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