Flutter modal sheet Texfield issue

Question

I have been experimenting with modal sheet witha textfield at the bottom. Modal sheet works fine but somehow I am unable to see the texts that I type. The keypad hides the textfield. I have tried the singlechildscrollview and expanded approach, it doesn't quite solve it. Also, I tried enclosing bottom sheet with scaffold; it somehow takes the entire screen even though I have set the bottom sheet height to 90% of device screen size. How do I solve it?!

Code:

    modalSheet() {
    showModalBottomSheet(
        context: context,
        isScrollControlled: true,
        backgroundColor: Colors.white,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.only(
              topLeft: Radius.circular(15.0), topRight: Radius.circular(15.0)),
        ),
        builder: (context) {
          return Container(
            padding: EdgeInsets.only(
                bottom: MediaQuery.of(context).viewInsets.bottom),
            height: MediaQuery.of(context).size.height * 0.9,
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                Container(
                  height: MediaQuery.of(context).size.height * 0.1,
                  color: Colors.green,
                ),
                Container(
                  height: MediaQuery.of(context).size.height * 0.7,
                  color: Colors.blue,
                ),
                Container(
                  height: MediaQuery.of(context).size.height * 0.1,
                  color: Colors.grey[200],
                  child: Padding(
                    padding: const EdgeInsets.only(left: 16.0, right: 16.0),
                    child: Center(
                      child: TextField(
                        decoration: InputDecoration(
                          border: InputBorder.none,
                          suffixIcon: Icon(Icons.insert_emoticon),
                          hintText: 'Write a comment...',
                          hintStyle: TextStyle(
                              fontSize: 18.0,
                              fontWeight: FontWeight.w600,
                              color: Colors.grey),
                        ),
                      ),
                    ),
                  ),
                )
              ],
            ),
          );
        });
  }