Keep members that are weakly referenced from native code

When full optimization is enabled in system_server, members that are
write-only may be optimized away. This can impact downstream weak
reference lifecycle semantics. Annotate such a member in
LocalDisplayAdapter that is weakly referenced from native code.

Test: FULL_SYSTEM_OPTIMIZE_JAVA=true m + check member preserved
Bug: 349245577
Change-Id: I355ee0ff7009476d4b917fc8dd078922d1b2c15b

1 files changed, 3 insertions, 1 deletions

diff --git a/services/core/java/com/android/server/display/LocalDisplayAdapter.java b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
index 22898a65c5de..ee63c08edee2 100644
--- a/services/core/java/com/android/server/display/LocalDisplayAdapter.java
+++ b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
@@ -45,6 +45,7 @@ import android.view.RoundedCorners;
 import android.view.SurfaceControl;
 
 import com.android.internal.R;
+import com.android.internal.annotations.KeepForWeakReference;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.display.BrightnessSynchronizer;
 import com.android.internal.util.function.pooled.PooledLambda;
@@ -1364,8 +1365,9 @@ final class LocalDisplayAdapter extends DisplayAdapter {
     }
 
     public static class Injector {
-        // Native callback.
+        // Ensure the callback is kept to preserve native weak reference lifecycle semantics.
         @SuppressWarnings("unused")
+        @KeepForWeakReference
         private ProxyDisplayEventReceiver mReceiver;
         public void setDisplayEventListenerLocked(Looper looper, DisplayEventListener listener) {
             mReceiver = new ProxyDisplayEventReceiver(looper, listener);