new Thread(new Runnable() {
    @Override
    public void run() {
        for (int i = 0; i < mClipboard.size(); i++) {
            final int index = i;
            // Copy, or cut, each file or directory into the destination directory
            final File newFile = copy(getFile(i), dest, false);
            scanImage(newFile, context);
            context.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    // Update the adapter and increment the progress dialog
                    if (newFile != null) adapter.add(newFile);
                    // Increment the progress dialog
                    dialog.setProgress(index);
                }
            });
        }

        context.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                // Remove paste option from action bar
                context.invalidateOptionsMenu();
                // Clear the clipboard
                clear();
                // Close the dialog
                dialog.dismiss();
            }
        });
    }
}).start();

public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
private ProgressDialog mProgressDialog;

@Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
    case DIALOG_DOWNLOAD_PROGRESS:
        mProgressDialog = new ProgressDialog(this);
        mProgressDialog.setMessage("Loading..");
        mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        mProgressDialog.setCancelable(false);
        mProgressDialog.show();
        return mProgressDialog;
    default:
    return null;
    }
}

private class DownloadZipFileTask extends AsyncTask<String, String, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(DIALOG_DOWNLOAD_PROGRESS);
    }

    @Override
    protected String doInBackground(String... urls) {
        //Your background task code here.
        publishProgress("" + progress);
    }

    protected void onProgressUpdate(String... progress) {
    mProgressDialog.setProgress(Integer.parseInt(progress[0]));
    }

    @Override
    protected void onPostExecute(String result) {
        dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
    }
}