Android Download Manager

MainActivity.java

String[] PERMISSIONS = {Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE};
    private int RC_PERMISSIONS = 1;
    private long downloadID;
    private BroadcastReceiver onDownloadComplete = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            //Fetching the download id received with the broadcast
            long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            //Checking if the received broadcast is for our enqueued download by matching download id
            if (downloadID == id) {
                Toast.makeText(MainActivity.this, "Download Completed", Toast.LENGTH_SHORT).show();
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        registerReceiver(onDownloadComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));

    }


    public void onDownload(View view) {
        if (Permissions.hasPermissions(this, PERMISSIONS)) {
            beginDownload();
        } else {
            ActivityCompat.requestPermissions(this, PERMISSIONS, RC_PERMISSIONS);
        }
    }


    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        boolean valid = true;
        if (requestCode == RC_PERMISSIONS && grantResults.length > 0) {
            for (int result : grantResults) {
                if (result == PackageManager.PERMISSION_GRANTED)
                    valid = true;
                else {
                    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
                    valid = false;
                }
            }

            if (valid) {
                beginDownload();
            }
        }
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterReceiver(onDownloadComplete);
    }

    private void beginDownload() {
        File file = new File(getExternalFilesDir(null), "Dummy");
        DownloadManager.Request request = new DownloadManager.Request(Uri.parse("http://speedtest.ftp.otenet.gr/files/test10Mb.db"))
                // Title of the Download Notification
                .setTitle("Dummy File")
                // Description of the Download Notification
                .setDescription("Downloading")
                .setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE | DownloadManager.Request.NETWORK_WIFI)
                // Visibility of the download Notification
                .setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE | DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)
                // Uri of the destination file
                .setDestinationUri(Uri.fromFile(file))
                // Set if download is allowed on roaming network
                .setAllowedOverRoaming(true);

        DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
        if (downloadManager != null) {
            downloadID = downloadManager.enqueue(request);// enqueue puts the download request in the queue.
        }
    }

Permissions.java

public class Permissions {
    public static boolean hasPermissions(Context context, String... permissions) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
            for (String permission : permissions) {
                if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
        }
        return true;
    }
}