Tabs animation and selected index fixes (#8377)

* fix(tabs): animation freeze when chaning tabs

* fix(tabs): poper item selecting programically

api-reports/NativeScript.api.md

@@ -2934,7 +2934,7 @@ export abstract class ViewBase extends Observable {
     // (undocumented)
     _setupAsRootView(context: any): void;
     _setupUI(context: any /* android.content.Context */, atIndex?: number): void;
-    _shouldDelayLoad(): boolean;
+    _shouldDelayLayout(): boolean;
     showModal(moduleName: string, modalOptions: ShowModalOptions): ViewBase;
     showModal(view: ViewBase, modalOptions: ShowModalOptions): ViewBase;
     public readonly style: Style;

nativescript-core/ui/core/view-base/view-base.d.ts

@@ -474,7 +474,7 @@ export abstract class ViewBase extends Observable {
      * When returning true the callLoaded method will be run in setTimeout
      * Method is intended to be overridden by inheritors and used as "protected"
      */
-    _shouldDelayLoad(): boolean;
+    _shouldDelayLayout(): boolean;
 
     /**
      * @private

nativescript-core/ui/core/view-base/view-base.ts

@@ -561,12 +561,24 @@ export abstract class ViewBase extends Observable implements ViewBaseDefinition
         }
     }
 
+    private performLayout(currentRun = 0) {
+        // if there's an animation in progress we need to delay the layout
+        // we've added a guard of 5000 milliseconds execution
+        // to make sure that the layout will happen even if the animation haven't finished in 5 seconds
+        if (this._shouldDelayLayout() && currentRun < 100) {
+            setTimeout(() => this.performLayout(currentRun), currentRun);
+            currentRun++;
+        } else {
+            this.parent.requestLayout();
+        }
+    }
+
     @profile
     public requestLayout(): void {
         // Default implementation for non View instances (like TabViewItem).
         const parent = this.parent;
         if (parent) {
-            parent.requestLayout();
+            this.performLayout();
         }
     }
 
@@ -615,15 +627,11 @@ export abstract class ViewBase extends Observable implements ViewBaseDefinition
 
     public loadView(view: ViewBase): void {
         if (view && !view.isLoaded) {
-            if (this._shouldDelayLoad()) {
+            view.callLoaded();
-                setTimeout(() => view.callLoaded());
-            } else {
-                view.callLoaded();
-            }
         }
     }
 
-    public _shouldDelayLoad(): boolean {
+    public _shouldDelayLayout(): boolean {
         return false;
     }
 

nativescript-core/ui/page/page.ios.ts

@@ -348,7 +348,7 @@ export class Page extends PageBase {
         //
     }
 
-    public _shouldDelayLoad(): boolean {
+    public _shouldDelayLayout(): boolean {
         return this._frame && this._frame._animationInProgress;
     }
 

nativescript-core/ui/tabs/tabs.ios.ts

@@ -2,7 +2,7 @@
 import { TabContentItem } from "../tab-navigation-base/tab-content-item";
 import { TabStrip } from "../tab-navigation-base/tab-strip";
 import { TabStripItem } from "../tab-navigation-base/tab-strip-item";
-import { TextTransform } from "../text-base";
+import { TextTransform, ViewBase } from "../text-base";
 
 // Requires
 import { Color } from "../../color";
@@ -873,6 +873,9 @@ export class Tabs extends TabsBase {
             // TODO: investigate why this call is necessary to actually toggle item appearance
             this.viewController.tabBar.sizeToFit();
             this.tabStrip.setNativeView(this.viewController.tabBar);
+            if (this.selectedIndex) {
+                this.viewController.tabBar.setSelectedItemAnimated(this.tabBarItems[this.selectedIndex], false);
+            }
         }
 
         // const length = items ? items.length : 0;
@@ -1066,6 +1069,17 @@ export class Tabs extends TabsBase {
         this._ios.tabBar.tintColor = nativeColor;
     }
 
+    private visitFrames(view: ViewBase, operation: (frame: Frame) => {}) {
+        if (view instanceof Frame) {
+            operation(view);
+        }
+        view.eachChild(child => {
+            this.visitFrames(child, operation);
+
+            return true;
+        });
+    }
+
     [selectedIndexProperty.setNative](value: number) {
         // TODO
         // if (traceEnabled()) {
@@ -1092,17 +1106,11 @@ export class Tabs extends TabsBase {
 
             this._currentNativeSelectedIndex = value;
 
-            let itemControllerOwner = null;
+            // do not make layout changes while the animation is in progress https://stackoverflow.com/a/47031524/613113
-            if (itemController._owner) {
+            this.visitFrames(item, frame => frame._animationInProgress = true);
-                let itemControllerOwner = <Frame>itemController._owner.get();
-                // do not load new views while the animation is in progress https://stackoverflow.com/a/47031524/613113
-                itemControllerOwner._animationInProgress = true;
-            }
 
             this.viewController.setViewControllersDirectionAnimatedCompletion(controllers, navigationDirection, true, (finished: boolean) => {
-                if (itemControllerOwner) {
+                this.visitFrames(item, frame => frame._animationInProgress = false);
-                    itemControllerOwner._animationInProgress = false;
-                }
                 if (finished) {
                     // HACK: UIPageViewController fix; see https://stackoverflow.com/a/17330606
                     invokeOnRunLoop(() => this.viewController.setViewControllersDirectionAnimatedCompletion(controllers, navigationDirection, false, null));