Fix: Set the binding context of a page automatically when navigated to.

Resolves #731

tests/app/ui/layouts/grid-layout-tests.ts

@@ -17,13 +17,11 @@ class RemovalTrackingGridLayout extends GridLayout {
     public removedCols = 0;
 
     public _onRowRemoved(itemSpec: ItemSpec, index: number) {
-        console.log("_onRowRemoved");
         this.removedRows++;
         super._onRowRemoved(itemSpec, index);
     }
 
     public _onColumnRemoved(itemSpec: ItemSpec, index: number) {
-        console.log("_onColumnRemoved");
         this.removedCols++;
         super._onColumnRemoved(itemSpec, index);
     }

tests/app/ui/page/page-tests-common.ts

@@ -230,6 +230,31 @@ export function test_NavigateTo_WithContext() {
     TKUnit.assertNull(testPage.navigationContext, "Navigation context should be cleared on navigating back");
 }
 
+//https://github.com/NativeScript/NativeScript/issues/731
+export function test_BindingContext_Becomes_NavigationContext_When_NavigatingTo() {
+    let currentPage = frameModule.topmost().currentPage;
+    let testPage: Page;
+    let bindingContext;
+    let pageFactory = function (): Page {
+        testPage = new Page();
+        testPage.on(pageModule.Page.navigatingToEvent, function (args: NavigatedData) {
+            bindingContext = (<Page>args.object).bindingContext; 
+        });
+        return testPage;
+    };
+    let navEntry = {
+        create: pageFactory,
+        context: "This is the navigation context",
+        animated: false
+    };
+    let topFrame = frameModule.topmost();
+    topFrame.navigate(navEntry);
+    TKUnit.waitUntilReady(() => topFrame.currentPage !== null && topFrame.currentPage !== currentPage && testPage.isLayoutValid);
+    helper.goBack();
+    
+    TKUnit.assertEqual(bindingContext, navEntry.context, "The Page's bindingContext should be set automatically to the navigation context when navigating to.");
+}
+
 export function test_FrameBackStack_WhenNavigatingForwardAndBack() {
     let testPage: Page;
     let pageFactory = function () {

tests/package.json

@@ -6,7 +6,7 @@
   "nativescript": {
     "id": "org.nativescript.tests",
     "tns-ios": {
-      "version": "2.1.0"
+      "version": "2.1.1"
     },
     "tns-android": {
       "version": "2.1.1"
@@ -23,4 +23,4 @@
     "lazy": "1.0.11",
     "typescript": "^1.8.10"
   }
-}
+}

tns-core-modules/ui/page/page-common.ts

@@ -199,8 +199,15 @@ export class Page extends ContentView implements dts.Page {
         };
     }
 
+    private _originalBindingContext: any;
     public onNavigatingTo(context: any, isBackNavigation: boolean) {
         this._navigationContext = context;
+        
+        //https://github.com/NativeScript/NativeScript/issues/731
+        if (!isBackNavigation && context && this.bindingContext !== context){
+            this._originalBindingContext = this.bindingContext;
+            this.bindingContext = context;
+        }
         this.notify(this.createNavigatedData(Page.navigatingToEvent, isBackNavigation));
     }
 
@@ -216,6 +223,12 @@ export class Page extends ContentView implements dts.Page {
         this.notify(this.createNavigatedData(Page.navigatedFromEvent, isBackNavigation));
 
         this._navigationContext = undefined;
+        
+        //https://github.com/NativeScript/NativeScript/issues/731
+        if (isBackNavigation && this._originalBindingContext && this.bindingContext !== this._originalBindingContext){
+            this.bindingContext = this._originalBindingContext;
+            this._originalBindingContext = undefined;
+        }
     }
 
     public showModal(): Page {