How to make widgets not overlap in Stack - flutter-layout

Question

I have ListView.seperated and a TextFormField in a Stack, how can I make those widgets not overlap?
Stack(
children: [
Builder(builder: (context) {
if (messages == null) {
return const Center(child: CircularProgressIndicator());
}
return RefreshIndicator(
onRefresh: () async {
ref
.read(messagesProvider.notifier)
.clearMessagesForChat(chat['id']);
},
child: ListView.separated(
controller: chatScrollController,
itemCount: messages.length,
separatorBuilder: (context, index) {
return const Divider(
height: 1,
);
},
itemBuilder: (BuildContext context, int index) {
final message = messages[index];
return ListTile(
contentPadding:
const EdgeInsets.symmetric(horizontal: 16, vertical: 6),
leading: GestureDetector(
onTap: () => showModalBottomSheet(
context: context,
builder: (context) {
return UserProfile(message['author']);
}),
child:
getProfilePicture(context, message['author'], 30)),
title: Row(
children: [
Text(
message['author']['username'],
style: const TextStyle(fontWeight: FontWeight.bold),
),
const SizedBox(
width: 16,
),
Text(
DateFormat.yMMMd().format(
DateTime.parse(message['created_at']).toLocal()),
style:
const TextStyle(color: Colors.grey, fontSize: 12),
)
],
),
subtitle: Text(
message['content'],
style: const TextStyle(fontSize: 16),
),
onTap: () {},
);
},
),
);
}),
Align(
alignment: Alignment.bottomLeft,
child: Container(
padding: const EdgeInsets.only(left: 10, bottom: 10, top: 10),
height: 60,
width: double.infinity,
color: Colors.white,
child: Row(
children: <Widget>[
const SizedBox(
width: 15,
),
Expanded(
child: TextField(
controller: messageController,
keyboardType: TextInputType.multiline,
minLines: 1,
maxLines: null,
onSubmitted: (_) => sendMessage(chat['id']),
decoration: const InputDecoration(
hintText: 'Write message...',
hintStyle: TextStyle(color: Colors.black54),
border: InputBorder.none),
),
),
const SizedBox(
width: 15,
),
FloatingActionButton(
onPressed: () => sendMessage(chat['id']),
backgroundColor: Colors.blue,
elevation: 0,
child: const Icon(
Icons.send,
color: Colors.white,
size: 18,
),
),
],
),
),
),
],
),
Thanks