Optimize Dashboard loading

- prevent loading categories twice
- add some logging to see the time taken for building the Dashboard titles

Change-Id: I31724c0e66fe3b453a87f12476f58db84c73423f

src/com/android/settings/SettingsActivity.java

@@ -325,7 +325,9 @@ public class SettingsActivity extends Activity
         public void handleMessage(Message msg) {
             switch (msg.what) {
                 case MSG_BUILD_CATEGORIES: {
+                    if(mNeedToRebuildCategories) {
                         buildDashboardCategories(mCategories);
+                    }
                 } break;
             }
         }
@@ -342,7 +344,7 @@ public class SettingsActivity extends Activity
     }
 
     public List<DashboardCategory> getDashboardCategories() {
-        if (mNeedToRebuildCategories) {
+        if (mNeedToRebuildCategories || mCategories.size() == 0) {
             buildDashboardCategories(mCategories);
             mNeedToRebuildCategories = false;
         }
@@ -491,18 +493,13 @@ public class SettingsActivity extends Activity
                 switchToFragment( initialFragmentName, initialArguments, true, false,
                         mInitialTitle, false);
             } else {
-                // We need to build the Categories in all cases
-                buildDashboardCategories(mCategories);
-
                 // No UP if we are displaying the main Dashboard
                 mDisplayHomeAsUpEnabled = false;
-                if (mCategories.size() > 0) {
                 mInitialTitle = getText(R.string.dashboard_title);
                 switchToFragment(DashboardSummary.class.getName(), null, false, false,
                         mInitialTitle, false);
             }
         }
-        }
 
         mActionBar = getActionBar();
         if (mActionBar != null) {

src/com/android/settings/dashboard/DashboardSummary.java

@@ -27,6 +27,7 @@ import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
 import android.text.TextUtils;
+import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -79,6 +80,7 @@ public class DashboardSummary extends Fragment implements OnAccountsUpdateListen
     }
 
     private void rebuildUI(Context context) {
+        long start = System.currentTimeMillis();
         final Resources res = getResources();
 
         mDashboard.removeAllViews();
@@ -116,6 +118,8 @@ public class DashboardSummary extends Fragment implements OnAccountsUpdateListen
             // Add the category
             mDashboard.addView(categoryView);
         }
+        long delta = System.currentTimeMillis() - start;
+        Log.d(LOG_TAG, "rebuildUI took: " + delta + " ms");
     }
 
     @Override