Fix WM missing stack/task when activity is force stopped and restarted am: d9d35bdfcf

am: c35df3de2f

Change-Id: I9ca53012b924278e32465536ad12b98dd887ac9a

3 files changed, 37 insertions, 8 deletions

diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index e31df57f56d4..ece1ee95f320 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -781,20 +781,25 @@ public final class ActivityStackSupervisor implements DisplayListener {
         }
     }
 
+    static int nextTaskIdForUser(int taskId, int userId) {
+        int nextTaskId = taskId + 1;
+        if (nextTaskId == (userId + 1) * MAX_TASK_IDS_PER_USER) {
+            // Wrap around as there will be smaller task ids that are available now.
+            nextTaskId -= MAX_TASK_IDS_PER_USER;
+        }
+        return nextTaskId;
+    }
+
     int getNextTaskIdForUserLocked(int userId) {
         final int currentTaskId = mCurTaskIdForUser.get(userId, userId * MAX_TASK_IDS_PER_USER);
         // for a userId u, a taskId can only be in the range
         // [u*MAX_TASK_IDS_PER_USER, (u+1)*MAX_TASK_IDS_PER_USER-1], so if MAX_TASK_IDS_PER_USER
         // was 10, user 0 could only have taskIds 0 to 9, user 1: 10 to 19, user 2: 20 to 29, so on.
-        int candidateTaskId = currentTaskId;
+        int candidateTaskId = nextTaskIdForUser(currentTaskId, userId);
         while (mRecentTasks.taskIdTakenForUserLocked(candidateTaskId, userId)
                 || anyTaskForIdLocked(candidateTaskId, !RESTORE_FROM_RECENTS,
                         INVALID_STACK_ID) != null) {
-            candidateTaskId++;
-            if (candidateTaskId == (userId + 1) * MAX_TASK_IDS_PER_USER) {
-                // Wrap around as there will be smaller task ids that are available now.
-                candidateTaskId -= MAX_TASK_IDS_PER_USER;
-            }
+            candidateTaskId = nextTaskIdForUser(candidateTaskId, userId);
             if (candidateTaskId == currentTaskId) {
                 // Something wrong!
                 // All MAX_TASK_IDS_PER_USER task ids are taken up by running tasks for this user
diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index fba439f8ca60..1d57872b2fbc 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -191,6 +191,16 @@ class DisplayContent {
         return mHomeStack;
     }
 
+    TaskStack getStackById(int stackId) {
+        for (int i = mStacks.size() - 1; i >= 0; --i) {
+            final TaskStack stack = mStacks.get(i);
+            if (stack.mStackId == stackId) {
+                return stack;
+            }
+        }
+        return null;
+    }
+
     void updateDisplayInfo() {
         mDisplay.getDisplayInfo(mDisplayInfo);
         mDisplay.getMetrics(mDisplayMetrics);
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 10aaf5811e3c..c66f09cd792e 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -5047,18 +5047,32 @@ public class WindowManagerService extends IWindowManager.Stub
         try {
             synchronized (mWindowMap) {
                 final DisplayContent displayContent = mDisplayContents.get(displayId);
+                boolean attachedToDisplay = false;
                 if (displayContent != null) {
                     TaskStack stack = mStackIdToStack.get(stackId);
                     if (stack == null) {
                         if (DEBUG_STACK) Slog.d(TAG_WM, "attachStack: stackId=" + stackId);
-                        stack = new TaskStack(this, stackId);
+
+                        stack = displayContent.getStackById(stackId);
+                        if (stack != null) {
+                            // It's already attached to the display. Detach and re-attach
+                            // because onTop might change, and be sure to clear mDeferDetach!
+                            displayContent.detachStack(stack);
+                            stack.mDeferDetach = false;
+                            attachedToDisplay = true;
+                        } else {
+                            stack = new TaskStack(this, stackId);
+                        }
+
                         mStackIdToStack.put(stackId, stack);
                         if (stackId == DOCKED_STACK_ID) {
                             getDefaultDisplayContentLocked().mDividerControllerLocked
                                     .notifyDockedStackExistsChanged(true);
                         }
                     }
-                    stack.attachDisplayContent(displayContent);
+                    if (!attachedToDisplay) {
+                        stack.attachDisplayContent(displayContent);
+                    }
                     displayContent.attachStack(stack, onTop);
                     if (stack.getRawFullscreen()) {
                         return null;