Aggregated statistics: updated PlantUML and handle empty list. (#296)

doc/activities.txt

@@ -12,6 +12,7 @@ endlegend
 TrackListActivity --> TrackRecordingActivity : Start recording
 TrackListActivity --> SearchListActivity
 TrackListActivity --> MarkerListActivity : Show all markers
+TrackListActivity --> AggregatedStatisticsActivity : Aggregated stats
 TrackListActivity --> TrackRecordedActivity : Show track
 TrackListActivity --> TrackDeleteActivity
 

src/main/java/de/dennisguse/opentracks/AggregatedStatisticsActivity.java

@@ -20,6 +20,7 @@ public class AggregatedStatisticsActivity extends AbstractActivity {
         super.onCreate(savedInstanceState);
 
         listView = findViewById(R.id.aggregated_stats_list);
+        listView.setEmptyView(findViewById(R.id.aggregated_stats_empty_view));
 
         final AggregatedStatisticsModel viewModel = new ViewModelProvider(this).get(AggregatedStatisticsModel.class);
         viewModel.getAggregatedStats().observe(this, new Observer<AggregatedStatistics>() {

src/main/res/layout/aggregated_stats.xml

@@ -11,4 +11,32 @@
         android:layout_width="match_parent"
         android:layout_height="0dp"
         android:layout_weight="1.0" />
+
+    <RelativeLayout
+        android:id="@+id/aggregated_stats_empty_view"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="1.0">
+
+            <View
+                android:layout_width="0dp"
+                android:layout_height="match_parent"
+                android:layout_weight="1" />
+        
+            <TextView
+                style="@style/TextLarge"
+                android:layout_width="match_parent"
+                android:layout_height="match_parent"
+                android:layout_weight="4"
+                android:gravity="center_horizontal|center_vertical"
+                android:text="@string/aggregated_stats_empty_message"
+                android:textColor="@color/list_empty_text" />
+
+            <View
+                android:layout_width="0dp"
+                android:layout_height="match_parent"
+                android:layout_weight="1" />
+
+    </RelativeLayout>
+
 </LinearLayout>

src/main/res/values/strings.xml

@@ -430,6 +430,8 @@ limitations under the License.
     <string name="track_edit_new_track_title">New Track</string>
     <!-- Track List -->
     <string name="track_list_empty_message">Start recording your next adventure here</string>
+    <!-- Aggregated Statistics -->
+    <string name="aggregated_stats_empty_message">Record your first track to see aggregated statistics</string>
     <!-- Track Widget -->
     <!-- Tracks -->
     <string name="tracks_few">%1$d tracks</string>