fix sample errors

Author: zhuxingwei

Samples/UIWidgetSample/txt/TextFieldSample.cs

@@ -7,17 +7,17 @@
 
 namespace UIWidgetsSample {
     public class TextFieldSample : UIWidgetsSamplePanel {
-        protected override void Awake() {
-            base.Awake();
-            FontManager.instance.addFont(Resources.Load<Font>(path: "MaterialIcons-Regular"), "Material Icons");
-        }
-
         protected override Widget createWidget() {
             return new MaterialApp(
                 title: "Text Fields",
                 home: new MyCustomForm()
             );
         }
+
+        protected override void OnEnable() {
+            base.OnEnable();
+            FontManager.instance.addFont(Resources.Load<Font>(path: "MaterialIcons-Regular"), "Material Icons");
+        }
     }
 
     class MyCustomForm : StatefulWidget {

Tests/Editor/RenderEditable.cs

@@ -15,7 +15,7 @@
 using TextStyle = Unity.UIWidgets.painting.TextStyle;
 
 namespace UIWidgets.Tests {
-    public class RenderEditable : EditorWindow {
+    public class RenderEditable : EditorWindow, TextSelectionDelegate {
         readonly Func<RenderBox>[] _options;
 
         readonly string[] _optionStrings;
@@ -150,7 +150,8 @@ RenderBox textEditable() {
                     new _FixedViewportOffset(0.0f), new ValueNotifier<bool>(true),
                     onSelectionChanged: this.selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0),
                     maxLines: 100,
-                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+                    selectionColor: Color.fromARGB(255, 255, 0, 0),
+                    textSelectionDelegate: this)
             ));
 
             span = new TextSpan("", children:
@@ -164,7 +165,8 @@ RenderBox textEditable() {
                     new _FixedViewportOffset(0.0f), new ValueNotifier<bool>(true),
                     onSelectionChanged: this.selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0),
                     maxLines: 100,
-                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+                    selectionColor: Color.fromARGB(255, 255, 0, 0),
+                    textSelectionDelegate: this)
             ));
 
             span = new TextSpan("", children:
@@ -175,7 +177,8 @@ RenderBox textEditable() {
                 new Unity.UIWidgets.rendering.RenderEditable(span, TextDirection.ltr,
                     new _FixedViewportOffset(0.0f), new ValueNotifier<bool>(true),
                     onSelectionChanged: this.selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0),
-                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+                    selectionColor: Color.fromARGB(255, 255, 0, 0),
+                    textSelectionDelegate: this)
                 , width: 300));
             return flexbox;
         }
@@ -186,5 +189,13 @@ void selectionChanged(TextSelection selection, Unity.UIWidgets.rendering.RenderE
             Debug.Log($"selection {selection}");
             renderObject.selection = selection;
         }
+
+        public TextEditingValue textEditingValue { get; set; }
+        
+        public void hideToolbar() {
+        }
+
+        public void bringIntoView(TextPosition textPosition) {
+        }
     }
 }