Fix: Android pages disappear before their exit transition has finished

Resolves #2000

apps/perf-tests/nav-page.ts

@@ -40,9 +40,9 @@ export class NavPage extends Page implements definition.ControlsPage {
         var that = this;
         that.on(View.loadedEvent, (args) => {
             console.log(`${args.object}.loadedEvent`);
-            if (topmostFrame().android) {
+            //if (topmostFrame().android) {
-                topmostFrame().android.cachePagesOnNavigate = true;
+            //    topmostFrame().android.cachePagesOnNavigate = true;
-            }
+            //}
         });
         that.on(View.unloadedEvent, (args) => {
             console.log(`${args.object}.unloadedEvent`);

ui/frame/frame.android.ts

@@ -61,7 +61,7 @@ function onFragmentShown(fragment: FragmentClass) {
     transitionModule._onFragmentShown(fragment, isBack);
 }
 
-function onFragmentHidden(fragment: FragmentClass) {
+function onFragmentHidden(fragment: FragmentClass, destroyed: boolean) {
     trace.write(`HIDDEN ${fragment.getTag()}`, trace.categories.NativeLifecycle);
 
     if (fragment[CLEARING_HISTORY]) {
@@ -74,7 +74,7 @@ function onFragmentHidden(fragment: FragmentClass) {
     fragment.entry[IS_BACK] = undefined;
 
     // Handle page transitions.
-    transitionModule._onFragmentHidden(fragment, isBack);
+    transitionModule._onFragmentHidden(fragment, isBack, destroyed);
 }
 
 export class Frame extends frameCommon.Frame {
@@ -580,7 +580,7 @@ class FragmentClass extends android.app.Fragment {
         trace.write(`${this.getTag()}.onHiddenChanged(${hidden})`, trace.categories.NativeLifecycle);
         super.onHiddenChanged(hidden);
         if (hidden) {
-            onFragmentHidden(this);
+            onFragmentHidden(this, false);
         }
         else {
             onFragmentShown(this);
@@ -644,14 +644,8 @@ class FragmentClass extends android.app.Fragment {
     public onDestroyView(): void {
         trace.write(`${this.getTag()}.onDestroyView()`, trace.categories.NativeLifecycle);
         super.onDestroyView();
-        onFragmentHidden(this);
+        // Detaching the page has been move in onFragmentHidden due to transitions.
-
+        onFragmentHidden(this, true);
-        // When Fragment is destroyed we detach page even if cachePagesOnNavigate is true.
-        let entry = this.entry;
-        let page = entry.resolvedPage;
-        if (page._context) {
-            page._onDetached(true);
-        }
     }
 
     public onDestroy(): void {

ui/transition/transition.android.ts

@@ -13,6 +13,7 @@ var ENTER_POPEXIT_TRANSITION = "ENTER_POPEXIT_TRANSITION";
 var EXIT_POPENTER_TRANSITION = "EXIT_POPENTER_TRANSITION";
 var COMPLETE_PAGE_ADDITION_WHEN_TRANSITION_ENDS = "COMPLETE_PAGE_ADDITION_WHEN_TRANSITION_ENDS";
 var COMPLETE_PAGE_REMOVAL_WHEN_TRANSITION_ENDS = "COMPLETE_PAGE_REMOVAL_WHEN_TRANSITION_ENDS";
+var DESTROYED = "DESTROYED";
 var enterFakeResourceId = -10;
 var exitFakeResourceId = -20;
 var popEnterFakeResourceId = -30;
@@ -241,7 +242,7 @@ export function _onFragmentShown(fragment: android.app.Fragment, isBack: boolean
     }
 }
 
-export function _onFragmentHidden(fragment: android.app.Fragment, isBack: boolean) {
+export function _onFragmentHidden(fragment: android.app.Fragment, isBack: boolean, destroyed: boolean) {
     var transitionType = isBack ? "Pop Exit" : "Exit";
     var relevantTransition = isBack ? ENTER_POPEXIT_TRANSITION : EXIT_POPENTER_TRANSITION;
     if (fragment[relevantTransition]) {
@@ -256,6 +257,8 @@ export function _onFragmentHidden(fragment: android.app.Fragment, isBack: boolea
         }
     }
 
+    fragment[DESTROYED] = destroyed;
+
     if (fragment[COMPLETE_PAGE_REMOVAL_WHEN_TRANSITION_ENDS] === undefined) {
         // This might be a second call if the fragment is hidden and then destroyed.
         _completePageRemoval(fragment, true, isBack);
@@ -291,6 +294,17 @@ function _completePageRemoval(fragment: android.app.Fragment, force: boolean = f
             trace.write(`REMOVAL of ${page} has already been done`, trace.categories.Transition);
         }
     }
+
+    if (fragment[DESTROYED]) {
+        fragment[DESTROYED] = undefined;
+        if (page._context) {
+            page._onDetached(true);
+            trace.write(`DETACHMENT of ${page} completed`, trace.categories.Transition);
+        }
+        else {
+            trace.write(`DETACHMENT of ${page} has already been done`, trace.categories.Transition);
+        }
+    }
 }
 
 function _addNativeTransitionListener(fragment: android.app.Fragment, nativeTransition: any/*android.transition.Transition*/) {

ui/transition/transition.d.ts

@@ -23,7 +23,7 @@
     export function _setAndroidFragmentTransitions(navigationTransition: frame.NavigationTransition, currentFragment: any, newFragment: any, fragmentTransaction: any): void;
     export function _onFragmentCreateAnimator(fragment: any, nextAnim: number): any;
     export function _onFragmentShown(fragment: any, isBack: boolean): void;
-    export function _onFragmentHidden(fragment: any, isBack: boolean): void;
+    export function _onFragmentHidden(fragment: any, isBack: boolean, destroyed: boolean): void;
 
     export function _createIOSAnimatedTransitioning(navigationTransition: frame.NavigationTransition, nativeCurve: any, operation: number, fromVC: any, toVC: any): any;
     //@endprivate