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;
}