Android ContextThemeWrapper cannot be cast to android.app.Activity

java.lang.ClassCastException: android.view.ContextThemeWrapper cannot be cast to android.app.Activity Dialog中的context，在强制装换Activity出现。 将(Activity) mContext，变成：scanForActivity(mContext)

private static Activity scanForActivity(Context cont) {  
    if (cont == null)  
        return null;  
    else if (cont instanceof Activity)  
        return (Activity)cont;  
    else if (cont instanceof ContextWrapper)  
        return scanForActivity(((ContextWrapper)cont).getBaseContext());  
  
    return null;  
}