Move activities to fullscreen stack on display removal

Instead of moving dynamic stacks from secondary to primary display
on removal, move activities to fullscreen stack. This way activities
are guaranteed to appear in valid launch stack and will respect
split-screen mode bounds.

Bug: 34263289
Bug: 35258038
Test: android.server.cts.ActivityManagerDisplayTests
Test: #testStackFocusSwitchOnDisplayRemoved
Test: #testStackFocusSwitchOnDisplayRemoved2
Change-Id: Iebd3bef3e0cf8afd482630dd5ad8ec4315497950

diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 95734a4..cb1f510 100644 (file)
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3776,18 +3776,27 @@ public class ActivityStackSupervisor extends ConfigurationContainer implements D
     }
 
     private void handleDisplayRemoved(int displayId) {
+        if (displayId == DEFAULT_DISPLAY) {
+            throw new IllegalArgumentException("Can't remove the primary display.");
+        }
+
         synchronized (mService) {
             ActivityDisplay activityDisplay = mActivityDisplays.get(displayId);
             if (activityDisplay != null) {
                 final boolean destroyContentOnRemoval
                         = activityDisplay.shouldDestroyContentOnRemove();
-                ArrayList<ActivityStack> stacks = activityDisplay.mStacks;
-                for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
-                    final ActivityStack stack = stacks.get(stackNdx);
-                    moveStackToDisplayLocked(stack.mStackId, DEFAULT_DISPLAY,
-                            !destroyContentOnRemoval /* onTop */);
+                final ArrayList<ActivityStack> stacks = activityDisplay.mStacks;
+                while (!stacks.isEmpty()) {
+                    final ActivityStack stack = stacks.get(0);
                     if (destroyContentOnRemoval) {
+                        moveStackToDisplayLocked(stack.mStackId, DEFAULT_DISPLAY,
+                                false /* onTop */);
                         stack.finishAllActivitiesLocked(true /* immediately */);
+                    } else {
+                        // Moving all tasks to fullscreen stack, because it's guaranteed to be
+                        // a valid launch stack for all activities. This way the task history from
+                        // external display will be preserved on primary after move.
+                        moveTasksToFullscreenStackLocked(stack.getStackId(), true /* onTop */);
                     }
                 }
                 mActivityDisplays.remove(displayId);