Re-enable SummaryProvider for default_activity.

src/main/java/de/dennisguse/opentracks/util/HackUtils.java

@@ -0,0 +1,22 @@
+package de.dennisguse.opentracks.util;
+
+import androidx.annotation.NonNull;
+import androidx.preference.Preference;
+
+public class HackUtils {
+
+    private HackUtils() {
+    }
+
+    /**
+     * Triggers a redraw of the summary of a preference if it was set programmatically.
+     * Need to trigger androidx.preference.preferences.notifyChanged() to trigger a redraw, but method is protected.
+     * This workaround also works when this preference has not changed, but it's entries (see R.string.stats_rate_key).
+     * TODO
+     */
+    public static void invalidatePreference(@NonNull Preference preference) {
+        boolean isEnabled = preference.isEnabled();
+        preference.setEnabled(!isEnabled);
+        preference.setEnabled(isEnabled);
+    }
+}