Fix NPE in LogicalDisplayMapper

For getDisplayIdsByGroupIdLocked, use keyAt() instead of get() to get
the group ID within a loop. Also add null DisplayGroup check.

Flag: EXEMPT bug fix
Bug: 371033049
Test: atest android.app.cts.ActivityManagerTest
Change-Id: I280118a32788ce53735842fd7a6e1c23d7595216

1 files changed, 2 insertions, 2 deletions

diff --git a/services/core/java/com/android/server/display/LogicalDisplayMapper.java b/services/core/java/com/android/server/display/LogicalDisplayMapper.java
index bcb600d0f91c..06a910396d6c 100644
--- a/services/core/java/com/android/server/display/LogicalDisplayMapper.java
+++ b/services/core/java/com/android/server/display/LogicalDisplayMapper.java
@@ -355,8 +355,8 @@ class LogicalDisplayMapper implements DisplayDeviceRepository.Listener {
     public SparseArray<int[]> getDisplayIdsByGroupIdLocked() {
         SparseArray<int[]> displayIdsByGroupIds = new SparseArray<>();
         for (int i = 0; i < mDisplayGroups.size(); i++) {
-            int groupId = mDisplayGroups.get(i).getGroupId();
-            displayIdsByGroupIds.put(groupId, getDisplayIdsForGroupLocked(groupId));
+            final int displayGroupId = mDisplayGroups.keyAt(i);
+            displayIdsByGroupIds.put(displayGroupId, getDisplayIdsForGroupLocked(displayGroupId));
         }
         return displayIdsByGroupIds;
     }