WindowProvider.of(GameObject)

README.md

 2. You can add loading1@2.gif.bytes and loading1@3.gif.bytes in the same folder to support HD screens.
 3. Use Image.asset("loading1.gif") to load the gif images.
 
+#### Using Window Scope
+If you see the error ```AssertionError: Window.instance is null``` or null pointer error of ```Window.instance```,
+it means the code is not running in the window scope. In this case, you can enclose your code
+with window scope as below:
+```
+using(WindowProvider.of(your gameObject with UIWidgetsPanel).getScope()) {
+    // code dealing with UIWidgets, 
+    // e.g. setState(() => {....})
+}
+```
+All the code dealing with UIWidgets (```setState()``` in most case) needs to be in window scope.
+
+This is only needed if the code is in methods
+not invoked by UIWidgets. For example, if the code is in ```completed``` callback of ```UnityWebRequest```, 
+you need to enclose them with window scope. 
+Please see [HttpRequestSample](./Samples/UIWidgetSample/HttpRequestSample.cs) for detail.
+For callback/event handler methods from UIWidgets (e.g ```Widget.build, State.initState...```), you don't need put them
+in the window scope. 
 ## Debug UIWidgets Application
 
 #### Define UIWidgets_DEBUG

Runtime/editor/editor_window.cs

 
 namespace Unity.UIWidgets.editor {
 #if UNITY_EDITOR
-    public abstract class UIWidgetsEditorWindow : EditorWindow {
+    public abstract class UIWidgetsEditorWindow : EditorWindow, WindowHost {
         WindowAdapter _windowAdapter;
 
         public UIWidgetsEditorWindow() {
         }
 
         protected abstract Widget createWidget();
+
+        public Window window {
+            get { return this._windowAdapter; }
+        }
     }
 
     public class EditorWindowAdapter : WindowAdapter {
 
 #endif
 
+    public interface WindowHost {
+        Window window { get; }
+    }
+    
     public abstract class WindowAdapter : Window {
         static readonly List<WindowAdapter> _windowAdapters = new List<WindowAdapter>();
 

Runtime/engine/UIWidgetsPanel.cs

 
     [RequireComponent(typeof(RectTransform))]
     public class UIWidgetsPanel : RawImage, IPointerDownHandler, IPointerUpHandler, IDragHandler,
-        IPointerEnterHandler, IPointerExitHandler {
+        IPointerEnterHandler, IPointerExitHandler, WindowHost {
         static Event _repaintEvent;
 
         [SerializeField] protected float devicePixelRatioOverride;
                     ? this.devicePixelRatioOverride
                     : this._displayMetrics.devicePixelRatio;
             }
-        }
-
-        protected override void OnDisable() {
-            D.assert(this._windowAdapter != null);
-            this._windowAdapter.OnDisable();
-            this._windowAdapter = null;
-            base.OnDisable();
         }
 
         protected virtual Widget createWidget() {
                 physicalX: position.x,
                 physicalY: position.y
             ));
+        }
+
+        public Window window {
+            get { return this._windowAdapter; }
         }
     }
 }

Runtime/widgets/app.cs

 using System.Collections.Generic;
 using RSG;
+using Unity.UIWidgets.editor;
+using Unity.UIWidgets.engine;
+using UnityEngine;
+using Color = Unity.UIWidgets.ui.Color;
 using TextStyle = Unity.UIWidgets.painting.TextStyle;
 
 namespace Unity.UIWidgets.widgets {
 
             return provider.window;
         }
+        
+        public static Window of(GameObject gameObject) {
+            var panel = gameObject.GetComponent<UIWidgetsPanel>();
+            return panel == null ? null : panel.window;
+        }
+
+#if UNITY_EDITOR
+        public static Window of(UIWidgetsEditorWindow editorWindow) {
+            return editorWindow.window;
+        }
+#endif
 
         public override bool updateShouldNotify(InheritedWidget oldWidget) {
             D.assert(this.window == ((WindowProvider) oldWidget).window);

Samples/UIWidgetSample/HttpRequestSample.cs

+using System;
+using System.Collections.Generic;
+using Unity.UIWidgets.engine;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.widgets;
+using UnityEngine;
+using UnityEngine.Networking;
+
+public class HttpRequestSample : UIWidgetsPanel
+{
+    protected override Widget createWidget() {
+        return new MaterialApp(
+            title: "Http Request Sample",
+            home: new Scaffold(
+                body:new AsyncRequestWidget(this.gameObject)
+                )
+        );
+    }
+}
+
+public class AsyncRequestWidget : StatefulWidget {
+    
+    public readonly GameObject gameObjOfUIWidgetsPanel;
+
+    public AsyncRequestWidget(GameObject gameObjOfUiWidgetsPanel, Key key = null) : base(key) {
+        this.gameObjOfUIWidgetsPanel = gameObjOfUiWidgetsPanel;
+    }
+
+    public override State createState() {
+        return new _AsyncRequestWidgetState();
+    }
+}
+
+[Serializable]
+public class TimeData {
+    public long currentFileTime;
+}
+
+class _AsyncRequestWidgetState : State<AsyncRequestWidget> {
+    
+    long _fileTime;
+    
+    public override Widget build(BuildContext context) {
+        
+        return new Column(
+            children: new List<Widget>() {
+                new FlatButton(child: new Text("Click To Get Time"), onPressed: () => {
+                    UnityWebRequest www = UnityWebRequest.Get("http://worldclockapi.com/api/json/est/now");
+                    var asyncOperation  = www.SendWebRequest();
+                    asyncOperation.completed += operation => {
+                        Debug.Log(www.downloadHandler.text);
+                        var timeData = JsonUtility.FromJson<TimeData>(www.downloadHandler.text);
+                        using(WindowProvider.of(this.widget.gameObjOfUIWidgetsPanel).getScope())
+                        {
+                            this.setState(() => { this._fileTime = timeData.currentFileTime; });
+                        }
+                       
+                    };
+                }),
+                new Text($"current file time: {this._fileTime}")
+            });
+    }
+}

Samples/UIWidgetSample/HttpRequestSample.cs.meta

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