Avoid over logging preference changes.

When preference screen is created all prefence goes through
SharedPreferenceLogger once. We don't want to log it as preference
change because it's just initial display. Subsequent preference logger
calls should result in logging.

Bug: 30914916
Test: make RunSettingsRoboTests
Change-Id: Icaee9137c55555f4db7839ff0381a13ccd420190

src/com/android/settings/core/instrumentation/SharedPreferencesLogger.java

@@ -21,6 +21,7 @@ import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
 import android.os.AsyncTask;
 import android.text.TextUtils;
+import android.util.ArraySet;
 
 import com.android.internal.logging.MetricsProto.MetricsEvent;
 import com.android.settings.overlay.FeatureFactory;
@@ -33,11 +34,13 @@ public class SharedPreferencesLogger implements SharedPreferences {
     private final String mTag;
     private final Context mContext;
     private final MetricsFeatureProvider mMetricsFeature;
+    private final Set<String> mPreferenceKeySet;
 
     public SharedPreferencesLogger(Context context, String tag) {
         mContext = context;
         mTag = tag;
         mMetricsFeature = FeatureFactory.getFactory(context).getMetricsFeatureProvider();
+        mPreferenceKeySet = new ArraySet<>();
     }
 
     @Override
@@ -96,7 +99,15 @@ public class SharedPreferencesLogger implements SharedPreferences {
     }
 
     private void logValue(String key, String value) {
-        mMetricsFeature.count(mContext, mTag + "/" + key + "|" + value, 1);
+        final String prefKey = mTag + "/" + key;
+        if (!mPreferenceKeySet.contains(prefKey)) {
+            // Pref key doesn't exist in set, this is initial display so we skip metrics but
+            // keeps track of this key.
+            mPreferenceKeySet.add(prefKey);
+            return;
+        }
+        // Pref key exists in set, log it's change in metrics.
+        mMetricsFeature.count(mContext, prefKey + "|" + value, 1);
     }
 
     private void logPackageName(String key, String value) {