// in gradle - use compile in old one
implementation 'com.afollestad.material-dialogs:core:0.9.6.0'

// Field variable
MaterialDialog progressDialog;

progressDialog = new MaterialDialog.Builder(context)
                .title("Loading something")
                .content("")
                .progress(true, 0) // true for indeterminate
                .show();
 
// to dismiss it
if (progressDialog != null) {
    progressDialog.dismiss();
}