Interval Stats: fixed NPE introduced in 25ef0ecad1.

Includes some refactoring.

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

@@ -167,6 +167,7 @@ public class TrackRecordingActivity extends AbstractActivity implements ChooseAc
             //Activity was recreated.
             trackId = savedInstanceState.getParcelable(EXTRA_TRACK_ID);
         } else {
+            // Resume a track
             trackId = getIntent().getParcelableExtra(EXTRA_TRACK_ID);
             if (trackId != null && contentProviderUtils.getTrack(trackId) == null) {
                 Log.w(TAG, "TrackId does not exists; cannot continue the recording.");

src/main/java/de/dennisguse/opentracks/fragments/IntervalsRecordedFragment.java

@@ -60,7 +60,7 @@ public class IntervalsRecordedFragment extends Fragment implements IntervalListV
 
         viewModel = new ViewModelProvider(this).get(IntervalStatisticsModel.class);
 
-        updateIntervals(null);
+        intervalChanged(null);
     }
 
     @Override
@@ -77,7 +77,8 @@ public class IntervalsRecordedFragment extends Fragment implements IntervalListV
      *
      * @param interval intervals will split in this interval if not null. If it's null then view model will use the default one.
      */
-    private void updateIntervals(@Nullable IntervalStatisticsModel.IntervalOption interval) {
+    @Override
+    public void intervalChanged(IntervalStatisticsModel.IntervalOption interval) {
         if (viewModel == null || intervalListView == null) {
             return;
         }
@@ -95,9 +96,4 @@ public class IntervalsRecordedFragment extends Fragment implements IntervalListV
             }
         });
     }
-
-    @Override
-    public void intervalChanged(IntervalStatisticsModel.IntervalOption interval) {
-        updateIntervals(interval);
-    }
 }

src/main/java/de/dennisguse/opentracks/fragments/IntervalsRecordingFragment.java

@@ -106,7 +106,8 @@ public class IntervalsRecordingFragment extends Fragment implements IntervalList
      *
      * @param interval intervals will split in this interval if not null. If it's null then view model will use the default one.
      */
-    private void updateIntervals(@Nullable IntervalStatisticsModel.IntervalOption interval) {
+    @Override
+    public void intervalChanged(IntervalStatisticsModel.IntervalOption interval) {
         if (viewModel == null || intervalListView == null) {
             return;
         }
@@ -126,11 +127,7 @@ public class IntervalsRecordingFragment extends Fragment implements IntervalList
     }
 
     private void updateIntervals() {
-        updateIntervals(null);
+        intervalChanged(null);
     }
 
-    @Override
-    public void intervalChanged(IntervalStatisticsModel.IntervalOption interval) {
-        updateIntervals(interval);
-    }
 }

src/main/java/de/dennisguse/opentracks/fragments/StatisticsRecordedFragment.java

@@ -109,8 +109,6 @@ public class StatisticsRecordedFragment extends Fragment {
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
 
-        ViewGroup rootView = view.findViewById(R.id.root_view);
-
         totalTimeValueView = view.findViewById(R.id.stats_total_time_value);
 
         distanceValue = view.findViewById(R.id.stats_distance_value);

src/main/java/de/dennisguse/opentracks/fragments/StatisticsRecordingFragment.java

@@ -48,8 +48,6 @@ public class StatisticsRecordingFragment extends Fragment implements TrackDataLi
 
     private static final String TAG = StatisticsRecordingFragment.class.getSimpleName();
 
-    private static final String TRACK_ID_KEY = "trackId";
-
     private static final long UI_UPDATE_INTERVAL = UnitConversions.ONE_SECOND_MS;
 
     private TrackDataHub trackDataHub;

src/main/java/de/dennisguse/opentracks/viewmodels/IntervalStatisticsModel.java

@@ -4,6 +4,7 @@ import android.app.Application;
 import android.content.Context;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
@@ -22,17 +23,15 @@ import de.dennisguse.opentracks.util.UnitConversions;
  */
 public class IntervalStatisticsModel extends AndroidViewModel {
 
-    private MutableLiveData<IntervalStatistics> intervalStats;
-    private IntervalOption interval;
+    private MutableLiveData<IntervalStatistics> intervalStats = new MutableLiveData<>();
+    private IntervalOption interval = IntervalOption.OPTION_1;
 
     public IntervalStatisticsModel(@NonNull Application application) {
         super(application);
-        interval = IntervalOption.OPTION_1;
     }
 
-    public LiveData<IntervalStatistics> getIntervalStats(Track.Id trackId, IntervalOption interval) {
-        if (intervalStats == null || this.interval != interval) {
-            intervalStats = new MutableLiveData<>();
+    public LiveData<IntervalStatistics> getIntervalStats(@Nullable Track.Id trackId, IntervalOption interval) {
+        if (trackId != null && this.interval != interval) {
             this.interval = interval;
             loadIntervalStats(trackId);
         }
@@ -47,10 +46,10 @@ public class IntervalStatisticsModel extends AndroidViewModel {
      * Call this method when you want to force the view model to re-load intervals.
      */
     public void invalidate() {
-        intervalStats = null;
+        intervalStats = new MutableLiveData<>();
     }
 
-    private void loadIntervalStats(Track.Id trackId) {
+    private void loadIntervalStats(final Track.Id trackId) {
         new Thread(() -> {
             Context context = getApplication().getApplicationContext();
             ContentProviderUtils contentProviderUtils = new ContentProviderUtils(context);

src/main/res/layout/statistics_recorded.xml

@@ -5,7 +5,6 @@
     style="@style/StatsScrollView">
 
     <androidx.constraintlayout.widget.ConstraintLayout
-        android:id="@+id/root_view"
         android:layout_width="match_parent"
         android:layout_height="wrap_content">