Use WeakReference for caching DisplayManagerCompat instances

Relnote: Fixed Context leak in DisplayManagerCompat
Fixes: 279625765
Test: DisplayManagerCompatTest
Change-Id: I3409b324301609dba940ef5894ff349b0f229d13

Author: alanv

core/core/src/androidTest/java/androidx/core/hardware/display/DisplayManagerCompatTest.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.core.hardware.display
+
+import android.content.Context
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.SmallTest
+import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertSame
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@SmallTest
+@RunWith(AndroidJUnit4::class)
+class DisplayManagerCompatTest {
+
+    private lateinit var context: Context
+
+    @Before
+    fun setup() {
+        context = InstrumentationRegistry.getInstrumentation().context
+    }
+
+    @Test
+    fun testGetInstance() {
+        val displayManagerA = DisplayManagerCompat.getInstance(context)
+        assertNotNull(displayManagerA)
+
+        val displayManagerB = DisplayManagerCompat.getInstance(context)
+        assertSame(displayManagerA, displayManagerB)
+    }
+
+    @Test
+    fun testGetDisplay() {
+        val displayManager = DisplayManagerCompat.getInstance(context)
+        assertNotNull(displayManager)
+
+        val displays = displayManager.displays
+        assertNotNull(displays)
+
+        // If this device has displays, make sure we can obtain them. This is objectively an
+        // integration test, but it's the best we can do given the platform's testability.
+        displays.forEach { display ->
+            val actualDisplay = displayManager.getDisplay(display.displayId)
+            assertNotNull(actualDisplay)
+        }
+    }
+}

core/core/src/main/java/androidx/core/hardware/display/DisplayManagerCompat.java

@@ -27,14 +27,15 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 
+import java.lang.ref.WeakReference;
 import java.util.WeakHashMap;
 
 /**
  * Helper for accessing features in {@link android.hardware.display.DisplayManager}.
  */
 @SuppressWarnings("unused")
 public final class DisplayManagerCompat {
-    private static final WeakHashMap<Context, DisplayManagerCompat> sInstances =
+    private static final WeakHashMap<Context, WeakReference<DisplayManagerCompat>> sInstances =
             new WeakHashMap<>();
 
     /**
@@ -63,12 +64,12 @@ private DisplayManagerCompat(Context context) {
     @NonNull
     public static DisplayManagerCompat getInstance(@NonNull Context context) {
         synchronized (sInstances) {
-            DisplayManagerCompat instance = sInstances.get(context);
-            if (instance == null) {
-                instance = new DisplayManagerCompat(context);
+            WeakReference<DisplayManagerCompat> instance = sInstances.get(context);
+            if (instance == null || instance.get() == null) {
+                instance = new WeakReference<>(new DisplayManagerCompat(context));
                 sInstances.put(context, instance);
             }
-            return instance;
+            return instance.get();
         }
     }