How to make an emoji picker in Flutter?

I want to make an emoji picker.

I’ve searched Google and referred some Stack Overflow questions, but still can’t do it.

I’ve used the code from this answer, but it doesn’t work. It shows blank (not white, it’s transparent)

My code:

Offstage(
  offstage: false,
  child: SizedBox(
    height: 250,
    child: EmojiPicker(
      onEmojiSelected: (category, emoji) {
        messageTextController.text = messageTextController.text + emoji.emoji;
      },
      onBackspacePressed: () {},
      config: Config(
        columns: 7,
        verticalSpacing: 0,
        horizontalSpacing: 0,
        initCategory: Category.SMILEYS,
        bgColor: AppColors.kIconColor,
        indicatorColor: Colors.blue,
        iconColor: Colors.grey,
        iconColorSelected: Colors.blue,
        showRecentsTab: true,
        recentsLimit: 28,
        tabIndicatorAnimDuration: kTabScrollDuration,
        categoryIcons: const CategoryIcons(),
        buttonMode: kIsWeb || Platform.isAndroid ? ButtonMode.MATERIAL : ButtonMode.CUPERTINO,
      ),
    ),
  ),
),

How do I make an emoji picker in Flutter?