Android update app across app restarts using DownloadManager (avoid downloading multiple times)

Iam trying to update my app by downloading the apk using download manager. I have registered broadcast receiver to listen to DownloadManager.ACTION_DOWNLOAD_COMPLETE in MainActivity and open the apk in onReceive method. Following is the code:

public class MainActivity extends CordovaActivity {
private long downloadReference;
private DownloadManager downloadManager;
private IntentFilter intentFilter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);

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

    registerReceiver(downloadReceiver, intentFilter);

}

public void updateApp(String url) {
    //start downloading the file using the download manager
    downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
    Uri Download_Uri = Uri.parse(url);
    DownloadManager.Request request = new DownloadManager.Request(Download_Uri);
    request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
    request.setAllowedOverRoaming(false);
    request.setDestinationInExternalFilesDir(MainActivity.this, Environment.DIRECTORY_DOWNLOADS, "myapk.apk");
    downloadReference = downloadManager.enqueue(request);
}


@Override
public void onDestroy() {
    //unregister your receivers
    this.unregisterReceiver(downloadReceiver);
    super.onDestroy();
}

private BroadcastReceiver downloadReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {

        //check if the broadcast message is for our Enqueued download
        long referenceId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
        if (downloadReference == referenceId) {

            //start the installation of the latest version
                    Intent installIntent = new Intent(Intent.ACTION_VIEW);
                installIntent.setDataAndType(downloadManager.getUriForDownloadedFile(downloadReference),
                        "application/vnd.android.package-archive");
                installIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                context.startActivity(installIntent);

        }

    }

};

}

updateApp(url) is called on click of a button in UI. Now after clicking the button, the download starts. Lets say the app is closed (receiver is unregistered) after initiating the download, I have problem with two scenarios when the app is started again.

1. The previous download completes after my app is restarted -
   downloadReference is lost and when my receiver receives the broadcast, the referenceId wont be same as downloadReference, so installIntent is never started. So I have to click on Update button again and initiate the download. Is there a way to avoid this problem?

2. The previous download completes before my app is restarted - There is no way of knowing that my previous download is complete in the newly started activity. Again I have to click the button and reinitiate the download. Is there a way to enable sticky broadcast for download manager?