Merge "Ensure BrightnessTracker is only "start()"ed once"

services/core/java/com/android/server/display/BrightnessTracker.java

@@ -220,6 +220,11 @@ public class BrightnessTracker {
     }
 
     private void backgroundStart(float initialBrightness) {
+        synchronized (mDataCollectionLock) {
+            if (mStarted) {
+                return;
+            }
+        }
         if (DEBUG) {
             Slog.d(TAG, "Background start");
         }
@@ -250,6 +255,11 @@ public class BrightnessTracker {
 
     /** Stop listening for events */
     void stop() {
+        synchronized (mDataCollectionLock) {
+            if (!mStarted) {
+                return;
+            }
+        }
         if (DEBUG) {
             Slog.d(TAG, "Stop");
         }

services/tests/servicestests/src/com/android/server/display/BrightnessTrackerTest.java

@@ -21,6 +21,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -885,6 +886,29 @@ public class BrightnessTrackerTest {
         assertNull(mInjector.mLightSensor);
     }
 
+    @Test
+    public void testOnlyOneReceiverRegistered() {
+        assertNull(mInjector.mLightSensor);
+        assertNull(mInjector.mSensorListener);
+        startTracker(mTracker, 0.3f, false);
+
+        assertNotNull(mInjector.mLightSensor);
+        assertNotNull(mInjector.mSensorListener);
+        Sensor registeredLightSensor = mInjector.mLightSensor;
+        SensorEventListener registeredSensorListener = mInjector.mSensorListener;
+
+        mTracker.start(0.3f);
+        assertSame(registeredLightSensor, mInjector.mLightSensor);
+        assertSame(registeredSensorListener, mInjector.mSensorListener);
+
+        mTracker.stop();
+        assertNull(mInjector.mLightSensor);
+        assertNull(mInjector.mSensorListener);
+
+        // mInjector asserts that we aren't removing a null receiver
+        mTracker.stop();
+    }
+
     private InputStream getInputStream(String data) {
         return new ByteArrayInputStream(data.getBytes(StandardCharsets.UTF_8));
     }