How to sort file or folder by filename or date at ascending or descending in Android?

Question

The following sample code is from Internet, I hope to sort the List<String> files by filename at ascending or descending. I hope to the List<String> files by date of file at ascending or descending, how can I do ? Thanks!

The same quetsion with List<String> directories.

  List<String> files = Arrays.asList(f.list(new FilenameFilter() {
        @Override
        public boolean accept(File dir, String name) {
            File f=new File(dir, name);               

            return f.isFile()&&(f.isHidden()==false);
        }
    }));
    Collections.sort(files);




List<String> directories = Arrays.asList(f.list(new FilenameFilter() {
    @Override
    public boolean accept(File dir, String name) {
        File f=new File(dir, name);
        return f.isDirectory()&& (f.isHidden()==false);
    }
}));
Collections.sort(directories);

Answer 1

Just provide your File array and it sort simple.

Arrays.sort(files, new Comparator<File>() {
    public int compare(File f1, File f2) {
        return Long.compare(f1.lastModified(), f2.lastModified());
    }
});

Demo:

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        File path = Environment.getExternalStoragePublicDirectory("/DCIM/Camera");
        File[] filesList = path.listFiles();
        for (int i = 0; i < filesList.length; i++) {
            Date lastModDate = new Date(filesList[i].lastModified());
            Log.i("Pre sorted", "File last modified @ : " + lastModDate.toString());
        }

        Arrays.sort(filesList, new Comparator<File>() {
            public int compare(File f1, File f2) {
                return Long.compare(f1.lastModified(), f2.lastModified());
            }
        });
        Log.i("sorted", "----------------------------------------");
        for (int i = 0; i < filesList.length; i++) {
            Date lastModDate = new Date(filesList[i].lastModified());
            Log.i("Pro sorted", "File last modified @ : " + lastModDate.toString());
        }
    }

Answer 2

You can use like below for sorting based on file name and change that value for date and other comparision. Or simply use ApacheCommons, it will give direct APIs

File[] directoryList = currentFolder.listFiles(); 
if (directoryList != null) {
   List<File> directoryListing = new ArrayList<File>();
   directoryListing.addAll(Arrays.asList(directoryList));
   Collections.sort(directoryListing, new SortFileName());
   Collections.sort(directoryListing, new SortFolder());
}


//sorts based on the files name
public class SortFileName implements Comparator<File> {
    @Override
    public int compare(File f1, File f2) {
          return f1.getName().compareTo(f2.getName());
    }
}

//sorts based on a file or folder. folders will be listed first
public class SortFolder implements Comparator<File> {
    @Override
    public int compare(File f1, File f2) {
         if (f1.isDirectory() == f2.isDirectory())
            return 0;
         else if (f1.isDirectory() && !f2.isDirectory())
            return -1;
         else
            return 1;
          }
}

Answer 3

Might be late to answer bt this method sort files by desc order by modified date

File[] listFile = dir.listFiles();
Arrays.sort(listFile, new Comparator<File>() {
            @Override
            public int compare(File o1, File o2) {
                return Long.compare(o2.lastModified(), o1.lastModified());
            }
        });