Flutter: Multiline TextField (TextFormField) simply won't work - flutter

Question

I am fairly new at Flutter so I might have gotten things wrong but ... I can't get my head around this issue.
I have ready many posts on how allow multi-line text for TextField / TextFormField.
I have tried setting maxLines to null or to a big number, to enforce max lines (or not), but nothing works !
How come something as simple won't work ?
// in a Scaffold of a StatefulWidget
body: Padding(
padding: const EdgeInsets.all(50.0),
child: TextField(
keyboardType: TextInputType.multiline,
minLines: 1,
maxLines: 5,
),
I have tried on two different real Android devices and hitting the ENTER key does nothing. Unfortunately, I can't test the behavior on iOS as I don't have a Mac.
EDIT 1
Following solution offered by copsonroad, the following code
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
widget.event.shortName == null || widget.event.shortName.isEmpty
? AppLocalizations.of(context).eventEditorTitleNewEvent
: AppLocalizations.of(context)
.eventEditorTitleEditEvent(widget.event.shortName)),
actions: <Widget>[
if (_canSave == true) ...[
IconButton(
icon: Icon(Icons.done),
onPressed: () => _saveEventAndPop(),
)
],
]),
body: Center(
child: Padding(
padding: const EdgeInsets.all(50),
child: SizedBox(
height: 5 * 50.0,
child: TextField(
decoration: InputDecoration(hintText: "Enter a message"),
keyboardType: TextInputType.multiline,
maxLines: 5,
),
),
),
),
);
}
Produce the following result:

Answer 1

Screenshot:
#override
Widget build(BuildContext context) {
var maxLines = 5;
return Scaffold(
appBar: AppBar(),
body: Center(
child: Padding(
padding: const EdgeInsets.all(50),
child: SizedBox(
height: maxLines * 50.0,
child: TextField(
decoration: InputDecoration(hintText: "Enter a message"),
keyboardType: TextInputType.multiline,
maxLines: maxLines,
),
),
),
),
);
}
Edit:
Testing it on Android:

Answer 2

There is actually a bug with TextInputType.multiline. It simply doesn't work with some custom keyboards (i.e. SwiftKey). There is an issue in flutter github where I described my workaround.
First of all, I've wrapped my TextFormField with RawKeyboardListener like this:
RawKeyboardListener(
focusNode: FocusNode(),
autofocus: false,
onKey: (rawKeyEvent) {
final isFormSkippedEnterEvent = rawKeyEvent is RawKeyDownEvent &&
rawKeyEvent.isKeyPressed(LogicalKeyboardKey.enter);
final needToInsertNewLine = isFormSkippedEnterEvent &&
keyboardType == TextInputType.multiline;
if (needToInsertNewLine) {
TextEditingControllerHelper.insertText(controller, '\n');
}
},
child: TextFormField(...)
...
When Gboard is used, RawKeyboardListener doesn't receive Enter event at all, it's sent directly to the text field. But when using for example SwiftKey, instead of inserting new line to the text, RawKeyboardListener receives an event RawKeyDownEvent#a5131(logicalKey: LogicalKeyboardKey#70028(keyId: "0x100070028", keyLabel: "Enter", debugName: "Enter"). I check if I need to insert a new line (no need for this if TextFormField is configured to be single line) and access TextEditingController to alter user's input. All the magic happens inside TextEditingControllerHelper.insertText():
class TextEditingControllerHelper {
static insertText(TextEditingController controller, String textToInsert) {
final selection = controller.selection;
final cursorPosition = selection.base.offset;
if (cursorPosition < 0) {
controller.text += textToInsert;
return;
}
final text = controller.text;
final newText =
text.replaceRange(selection.start, selection.end, textToInsert);
controller.value = controller.value.copyWith(
text: newText,
selection: TextSelection.collapsed(
offset: selection.baseOffset + textToInsert.length,
),
);
}
}
What I do is check cursor/ selection position. In case of an empty field I just attach a newLine (this helper can work with other inputs, i.e. emojis) and exit. Otherwise I insert a new line on place of existing selection (if there is no selection, text is just inserted where cursor is placed) and move cursor to be after the inserted text. Works fine in my tests (Pixel 3a with Gboard/SwiftKey, Galaxy S8 with Samsung keyboard, iPhone simulator).