//        releaseVersionCode 5

String url="https://github.com/jehy/rutracker-free/releases/download/" + version+"/app-release.apk";

        new Updater().execute(this);

        class Updater extends AsyncTask<MainActivity, Void, Void> {

    private Exception exception;

    protected Void doInBackground(MainActivity... activity) {
        checkUpdates(activity[0]);
        return null;
    }

    Integer getLastAppVersion() {
        try {
            // Create a URL for the desired page
            URL url = new URL("https://raw.githubusercontent.com/jehy/rutracker-free/master/app/build.gradle");
            // Read all the text returned by the server
            BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
            String str;
            while ((str = in.readLine()) != null) {
                int f = str.indexOf("releaseVersionCode");
                if (f != -1) {
                    str = str.substring(f + ("releaseVersionCode").length()).trim();
                    Log.d("Rutracker free", "Last release version: " + str);
                    return Integer.parseInt(str);
                }
            }
            in.close();
            Log.d("Rutracker free", "Failed to get last release version!");
        } catch (Exception e) {
            Log.d("Rutracker free", "Failed to get last release version:");
            e.printStackTrace();
        }
        return null;
    }

    void checkUpdates(final MainActivity activity) {
        final Integer lastAppVersion = getLastAppVersion();
        if (lastAppVersion == null)
            return;
        if (lastAppVersion <= BuildConfig.VERSION_CODE) {
            Log.d("Rutracker free", "App version is okay, skipping update");
            return;
        }
        String li = SettingsManager.get(activity, "LastIgnoredUpdateVersion");
        if (li != null) {
            Integer liInt = Integer.parseInt(li);
            if (liInt >= lastAppVersion)
                return;
        }

        activity.Update(lastAppVersion);
    }

}

public class SettingsManager {
    static String get(Context mContext, String key) {
        SharedPreferences settings = PreferenceManager
                .getDefaultSharedPreferences(mContext);
        String data = settings.getString(key, null);
        if (data == null)
            Log.d("SettingsManager", "No settings " + key + " is stored! ");
        else
            Log.d("SettingsManager", "Got settings " + key + " equal to " + data);
        return data;
    }

    @SuppressLint("CommitPrefEdits")
    static void put(Context mContext, String key, String value) {
        SharedPreferences settings = PreferenceManager
                .getDefaultSharedPreferences(mContext);
        SharedPreferences.Editor editor = settings.edit();
        editor.putString(key, value);
        Log.d("SettingsManager", "Saved setting " + key + " equal to " + value);
        editor.commit();
    }
}

    public void Update(final Integer lastAppVersion) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setMessage("Доступно обновление приложения rutracker free до версии " +
                        lastAppVersion + " - желаете обновиться? " +
                        "Если вы согласны - вы будете перенаправлены к скачиванию APK файла,"
                        +" который затем нужно будет открыть.")
                        .setCancelable(true)
                        .setPositiveButton("Да", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                Intent intent = new Intent(Intent.ACTION_VIEW);
                                String apkUrl = "https://github.com/jehy/rutracker-free/releases/download/" +
                                        lastAppVersion + "/app-release.apk";
                                //intent.setDataAndType(Uri.parse(apkUrl), "application/vnd.android.package-archive");
                                intent.setData(Uri.parse(apkUrl));

                                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                startActivity(intent);
                                dialog.dismiss();
                            }
                        })
                        .setNegativeButton("Нет", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                SettingsManager.put(MainActivity.this, "LastIgnoredUpdateVersion", lastAppVersion.toString());
                                dialog.cancel();
                            }
                        });
                AlertDialog alert = builder.create();
                alert.show();
            }
        });
    }