From 9adc55fdc6ab44dbe2b02de72f84280857565bfe Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Tue, 28 Apr 2020 17:07:33 +0800
Subject: [PATCH] Fix stack reference is not updated if the task is organized

There is an additional stack level for split-screen mode, the child
of the organizer may be the instance referenced by task display area.
So if the child is removed, the stack reference should also be updated.

The corresponding operations of removeChild should be put in the
redirected implementation method, otherwise it will be missed when
propagating the removal to parent, that may cause reusing a detached
task and then crash because it does not have parent and display.

Bug: 154679904
Test: ActivityStackTests#testRemoveOrganizedTask_UpdateStackReference
Change-Id: I9c4032409345c772baa055e32da9eaba9a274b53
---
 .../core/java/com/android/server/wm/Task.java | 10 +++++-----
 .../android/server/wm/ActivityStackTests.java | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 2115a591a6b77..d14f5824b0125 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -1431,15 +1431,15 @@ class Task extends WindowContainer<WindowContainer> {
 
     @Override
     void removeChild(WindowContainer child) {
-        // A rootable child task that is now being removed from an organized task. Making sure
-        // the stack references is keep updated.
-        if (mTaskOrganizer != null && mCreatedByOrganizer && child.asTask() != null) {
-            getDisplayArea().removeStackReferenceIfNeeded((ActivityStack) child);
-        }
         removeChild(child, "removeChild");
     }
 
     void removeChild(WindowContainer r, String reason) {
+        // A rootable child task that is now being removed from an organized task. Making sure
+        // the stack references is keep updated.
+        if (mTaskOrganizer != null && mCreatedByOrganizer && r.asTask() != null) {
+            getDisplayArea().removeStackReferenceIfNeeded((ActivityStack) r);
+        }
         if (!mChildren.contains(r)) {
             Slog.e(TAG, "removeChild: r=" + r + " not found in t=" + this);
             return;
diff --git a/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java b/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
index 6c209e496cf61..5227f3c885baf 100644
--- a/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/ActivityStackTests.java
@@ -233,6 +233,25 @@ public class ActivityStackTests extends ActivityTestsBase {
         assertEquals(homeRoot.getParent(), secondaryTask.getParent());
     }
 
+    @Test
+    public void testRemoveOrganizedTask_UpdateStackReference() {
+        final ActivityStack rootHomeTask = mDefaultTaskDisplayArea.getRootHomeTask();
+        final ActivityRecord homeActivity = new ActivityBuilder(mService)
+                .setStack(rootHomeTask)
+                .setCreateTask(true)
+                .build();
+        final ActivityStack secondaryStack = (ActivityStack) WindowContainer.fromBinder(
+                mService.mTaskOrganizerController.createRootTask(rootHomeTask.getDisplayId(),
+                        WINDOWING_MODE_SPLIT_SCREEN_SECONDARY).token.asBinder());
+
+        rootHomeTask.reparent(secondaryStack, POSITION_TOP);
+        assertEquals(secondaryStack, rootHomeTask.getParent());
+
+        // This should call to {@link TaskDisplayArea#removeStackReferenceIfNeeded}.
+        homeActivity.removeImmediately();
+        assertNull(mDefaultTaskDisplayArea.getRootHomeTask());
+    }
+
     @Test
     public void testStackInheritsDisplayWindowingMode() {
         final ActivityStack primarySplitScreen = mDefaultTaskDisplayArea.createStack(