flutter - responsive height Form - dart

Question

I have this simple form, with a textarea and buttons:
When I open the keyboard, I want to decrease the size of the textarea, like a responsive layout. If I close the keyboard, the textarea should fill the remaining screen space available.
desired effect: open / active keyboard
desired effect: closed/no keyboard
My intention is to make the components fill in the screen, regardless device resolution.
Can someone provide a valida example of it? I tried several implementations and I was not able to achive the desired effect.
UPDATE:
My current code for this screen:
new MaterialPageRoute(
builder: (context) {
return new Scaffold(
resizeToAvoidBottomPadding: true,
appBar: new AppBar(
title: new Text('Add new Grocery List'),
actions: <Widget>[
new IconButton(
icon: new Icon(Icons.delete),
tooltip: 'Clear Grocery List',
onPressed: () {
this._promptRemoveGroceryBatchList();
},
),
]
),
body: new Container(
padding: const EdgeInsets.all(5.0),
child: new Form(
key: this._formGroceryBatchAdd,
child: new ListView(
children: <Widget>[
new Container(
child: new Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
new TextFormField(
maxLines: 10,
autofocus: true,
decoration: new InputDecoration(
labelText: 'Item List',
hintText: 'Enter a grocery list',
contentPadding: const EdgeInsets.all(16.0)
),
validator: (value) {
if (value.isEmpty) {
return 'Please enter at least one grocery item';
}
},
onSaved: (value) {
this._formBatchGroceryData = value;
},
),
new Padding(
padding: new EdgeInsets.all(8.0),
child: new Text(
'One item per line. Use ":" to specifcy the amount.\n' +
'Example:\n' +
'Potatoes:12\n' +
'Tomatoes:6',
style: new TextStyle(fontSize: 12.0, color: Colors.black54),
),
),
],
),
),
new Container(
child: new ButtonBar(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
new RaisedButton(
child: new Text('Add Items'),
color: Theme.of(context).primaryColor,
textColor: Colors.white,
elevation: 4.0,
onPressed: () {
// ACTION GOES HERE
},
),
new RaisedButton(
child: new Text('Cancel'),
onPressed: () {
// ACTION GOES HERE
},
),
]
),
),
]
)
);
)
);
}
)

Answer 1

I'm afraid it can't be directly done using a TextField for the textarea because its size depends on the lines of text you have.
But you can simulate it by surrounding the TextField that allows unlimited lines with a Container.
This is a sample that could work for you:
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Flutter Demo Home Page'),
),
body: new Column(
children: <Widget>[
Expanded(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
decoration: BoxDecoration(
border: Border.all(),
borderRadius: BorderRadius.circular(4.0),
),
child: Padding(
padding: const EdgeInsets.only(
left: 10.0, bottom: 20.0, right: 10.0),
child: new TextField(
maxLines: null,
decoration: InputDecoration(
border: InputBorder.none,
),
),
),
),
),
),
],
),
);
}
}