com.unity.uiwidgets/Samples/UIWidgetSample/TextInputCanvas.cs

using System.Collections.Generic;
using Unity.UIWidgets.engine;
using Unity.UIWidgets.foundation;
using Unity.UIWidgets.painting;
using Unity.UIWidgets.rendering;
using Unity.UIWidgets.ui;
using Unity.UIWidgets.widgets;
using TextStyle = Unity.UIWidgets.painting.TextStyle;

namespace UIWidgetsSample
{
    public class TextInputCanvas: WidgetCanvas
    {
        public class TextInputSample : StatefulWidget
        {
            public readonly string title;
            public TextInputSample(Key key = null, string title = null) : base(key)
            {
                this.title = title;
            }

            public override State createState()
            {
                return new _TextInputSampleState();
            }
        }

        protected override Widget getWidget()
        {
            return new TextInputSample(key:null, title:gameObject.name);
        }

        class _TextInputSampleState : State<TextInputSample>
        {
            public class ToDoItem
            {
                public int id;
                public string content;
            }

            private int nextId = 0;
            private TextEditingController titleController = new TextEditingController("");
            private TextEditingController descController = new TextEditingController("");
            private FocusNode _titleFocusNode;
            private FocusNode _descFocusNode;

            public override void initState() {
                base.initState();
                _titleFocusNode = new FocusNode();
                _descFocusNode = new FocusNode();
            }

            public override void dispose()
            {
                _titleFocusNode.dispose();
                _descFocusNode.dispose();
                base.dispose();
            }
            
            private Widget title()
            {
                return new Text(widget.title??"", textAlign: TextAlign.center, 
                    style: new TextStyle(fontSize:24, fontWeight: FontWeight.w700));
            }
            
            private Widget titleInput()
            {
                return new Row(                
                    children: new List<Widget>(
                    )
                    {
                        new SizedBox(width:100, child: new Text("Title")),
                        new Flexible(child: new Container(
                            decoration: new BoxDecoration(border: Border.all(new Color(0xFF000000), 1)),
                            padding: EdgeInsets.fromLTRB(8, 0, 8, 0),
                            child: new EditableText(maxLines: 1,
                                controller: titleController,
                                autofocus: true,
                                focusNode: new FocusNode(),
                                style: new TextStyle(
                                    fontSize: 18,
                                    height: 1.5f,
                                    color: new Color(0xFF1389FD)
                                ),
                                selectionColor: Color.fromARGB(255, 255, 0, 0),
                                cursorColor: Color.fromARGB(255, 0, 0, 0))
                        )),
                        
                    }
                );
            }

            private Widget descInput()
            {
                return new Container(
                    margin: EdgeInsets.fromLTRB(0, 10, 0, 10),
                    child: new Row(                
                    children: new List<Widget>(
                    )
                    {
                        new SizedBox(width:100, child: new Text("Description")),
                        new Flexible(child: new Container(
                            height: 200,
                            decoration: new BoxDecoration(border: Border.all(new Color(0xFF000000), 1)),
                            padding: EdgeInsets.fromLTRB(8, 0, 8, 0),
                            child: new EditableText(maxLines: 200,
                                controller: descController,
                                focusNode: new FocusNode(),
                                style: new TextStyle(
                                    fontSize: 18,
                                    height: 1.5f,
                                    color: new Color(0xFF1389FD)
                                ),
                                selectionColor: Color.fromARGB(255, 255, 0, 0),
                                cursorColor: Color.fromARGB(255, 0, 0, 0))
                        )),
                        
                    }
                ));
            }
            public override Widget build(BuildContext context)
            {
                var container = new Container(
                    padding: EdgeInsets.all(10),
                    decoration: new BoxDecoration(color:new Color(0x7F000000), border:Border.all(color: Color.fromARGB(255, 255, 0, 0), width: 5),
                        borderRadius: BorderRadius.all(2)),
                    child: new Column(
                        crossAxisAlignment: CrossAxisAlignment.stretch,
                        children: new List<Widget>
                        {
                            title(),
                            titleInput(),
                            descInput(),
                        }
                    )
                );
                return container;
            }
        }
    }

}