how to create progress dialog programmatically in android

private AlertDialog progressDialog;
progressDialog = new SpotsDialog(mContext, R.style.Custom);

//Am using it in an AsyncTask. So in  my onPreExecute, I do this:
public void onPreExecute() {
  super.onPreExecute();
  progressDialog.show();
  ...
 }

//dismiss in onPostExecute
public void onPostExecute(){
   progressDialog.dismiss();
 } 

dependencies {
...
   compile 'com.github.d-max:spots-dialog:0.4@aar'
}

<style name="Custom" parent="android:Theme.DeviceDefault.Dialog">
    <item name="DialogTitleAppearance">@android:style/TextAppearance.Medium</item>
    <item name="DialogTitleText">Please Wait</item>
    <item name="DialogSpotColor">@android:color/holo_orange_dark</item>
    <item name="DialogSpotCount">8</item>
</style>