diff --git a/android_app/app/src/androidTest/java/com/health/openscale/gui/ScreenshotRecorder.java b/android_app/app/src/androidTest/java/com/health/openscale/gui/ScreenshotRecorder.java
index 61339e4f..dcd91635 100644
--- a/android_app/app/src/androidTest/java/com/health/openscale/gui/ScreenshotRecorder.java
+++ b/android_app/app/src/androidTest/java/com/health/openscale/gui/ScreenshotRecorder.java
@@ -213,7 +213,8 @@ public class ScreenshotRecorder {
     }
 
     private void prepareData() {
-        openScale.addScaleUser(getTestUser());
+        int userId = openScale.addScaleUser(getTestUser());
+        openScale.selectScaleUser(userId);
 
         List<ScaleMeasurement> scaleMeasurementList = getTestMeasurements();
 
diff --git a/android_app/app/src/main/java/com/health/openscale/core/OpenScale.java b/android_app/app/src/main/java/com/health/openscale/core/OpenScale.java
index aea89b09..eb91a638 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/OpenScale.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/OpenScale.java
@@ -138,12 +138,18 @@ public class OpenScale {
         scaleDB.close();
     }
 
-    public void addScaleUser(final ScaleUser user)
-    {
-        long userId = userDAO.insert(user);
+    public int addScaleUser(final ScaleUser user) {
+        return (int)userDAO.insert(user);
+    }
 
+    public void selectScaleUser(int userId) {
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        prefs.edit().putInt("selectedUserId", (int)userId).commit();
+        prefs.edit().putInt("selectedUserId", userId).commit();
+    }
+
+    public int getSelectedScaleUserId() {
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        return prefs.getInt("selectedUserId", -1);
     }
 
     public List<ScaleUser> getScaleUserList()
@@ -161,8 +167,7 @@ public class OpenScale {
         ScaleUser scaleUser = new ScaleUser();
 
         try {
-            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-            int selectedUserId  = prefs.getInt("selectedUserId", -1);
+            int selectedUserId = getSelectedScaleUserId();
 
             if (selectedUserId == -1) {
                 return scaleUser;
@@ -355,8 +360,7 @@ public class OpenScale {
     }
 
     public int[] getCountsOfMonth(int year) {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+        int selectedUserId = getSelectedScaleUserId();
 
         int [] numOfMonth = new int[12];
 
@@ -375,8 +379,7 @@ public class OpenScale {
     }
 
     public List<ScaleMeasurement> getScaleDataOfMonth(int year, int month) {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+        int selectedUserId = getSelectedScaleUserId();
 
         Calendar startCalender = Calendar.getInstance();
         Calendar endCalender = Calendar.getInstance();
@@ -389,8 +392,7 @@ public class OpenScale {
     }
 
     public List<ScaleMeasurement> getScaleDataOfYear(int year) {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+        int selectedUserId = getSelectedScaleUserId();
 
         Calendar startCalender = Calendar.getInstance();
         Calendar endCalender = Calendar.getInstance();
@@ -430,18 +432,15 @@ public class OpenScale {
     public void registerFragment(FragmentUpdateListener fragment) {
         fragmentList.add(fragment);
 
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+        int selectedUserId = getSelectedScaleUserId();
 
         scaleMeasurementList = measurementDAO.getAll(selectedUserId);
 
         fragment.updateOnView(scaleMeasurementList);
     }
 
-    public void updateScaleData()
-    {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+    public void updateScaleData() {
+        int selectedUserId = getSelectedScaleUserId();
 
         scaleMeasurementList = measurementDAO.getAll(selectedUserId);
 
diff --git a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothExingtechY1.java b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothExingtechY1.java
index e535a334..4b858f2a 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothExingtechY1.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothExingtechY1.java
@@ -62,8 +62,7 @@ public class BluetoothExingtechY1 extends BluetoothCommunication {
                 byte height = (byte)(selectedUser.getBodyHeight() & 0xff); // cm
                 byte age = (byte)(selectedUser.getAge(new Date()) & 0xff);
 
-                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-                int userId = prefs.getInt("selectedUserId", -1);
+                int userId = selectedUser.getId();
 
                 byte cmdByte[] = {(byte)0x10, (byte)userId, gender, age, height};
 
diff --git a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale.java b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale.java
index e8179d96..652959d3 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale.java
@@ -285,7 +285,7 @@ public class BluetoothMiScale extends BluetoothCommunication {
             prefs.edit().putInt("uniqueNumber", uniqueNumber).commit();
         }
 
-        int userId = prefs.getInt("selectedUserId", -1);
+        int userId = OpenScale.getInstance(context).getSelectedScaleUserId();
 
         return uniqueNumber + userId;
     }
diff --git a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale2.java b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale2.java
index 45e939f0..b0d6afde 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale2.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMiScale2.java
@@ -257,7 +257,7 @@ public class BluetoothMiScale2 extends BluetoothCommunication {
             prefs.edit().putInt("uniqueNumber", uniqueNumber).commit();
         }
 
-        int userId = prefs.getInt("selectedUserId", -1);
+        int userId = OpenScale.getInstance(context).getSelectedScaleUserId();
 
         return uniqueNumber + userId;
     }
diff --git a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiMini.java b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiMini.java
index 4d15e824..dd575c4c 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiMini.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiMini.java
@@ -154,7 +154,7 @@ public class BluetoothYunmaiMini extends BluetoothCommunication {
             prefs.edit().putInt("uniqueNumber", uniqueNumber).commit();
         }
 
-        int userId = prefs.getInt("selectedUserId", -1);
+        int userId = OpenScale.getInstance(context).getSelectedScaleUserId();
 
         return uniqueNumber + userId;
     }
diff --git a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiSE.java b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiSE.java
index 24d8f8a8..d9fc00bf 100644
--- a/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiSE.java
+++ b/android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothYunmaiSE.java
@@ -152,7 +152,7 @@ public class BluetoothYunmaiSE extends BluetoothCommunication {
             prefs.edit().putInt("uniqueNumber", uniqueNumber).commit();
         }
 
-        int userId = prefs.getInt("selectedUserId", -1);
+        int userId = OpenScale.getInstance(context).getSelectedScaleUserId();
 
         return uniqueNumber + userId;
     }
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java b/android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java
index afb8759c..4d351f57 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java
@@ -301,8 +301,9 @@ public class DataEntryActivity extends Activity {
     private class onClickListenerAdd implements View.OnClickListener {
         @Override
         public void onClick(View v) {
-            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-            int selectedUserId = prefs.getInt("selectedUserId", -1);
+            OpenScale openScale = OpenScale.getInstance(getApplicationContext());
+
+            int selectedUserId = openScale.getSelectedScaleUserId();
 
             if (selectedUserId == -1) {
                 AlertDialog.Builder infoDialog = new AlertDialog.Builder(context);
@@ -317,7 +318,6 @@ public class DataEntryActivity extends Activity {
                     measurement.saveTo(scaleMeasurement);
                 }
 
-                OpenScale openScale = OpenScale.getInstance(getApplicationContext());
                 openScale.addScaleData(scaleMeasurement);
 
                 finish();
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/activities/UserSettingsActivity.java b/android_app/app/src/main/java/com/health/openscale/gui/activities/UserSettingsActivity.java
index 49a538ea..80465764 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/activities/UserSettingsActivity.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/activities/UserSettingsActivity.java
@@ -246,9 +246,7 @@ public class UserSettingsActivity extends Activity {
                         lastUserId = scaleUser.get(0).getId();
                     }
 
-                    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-                    prefs.edit().putInt("selectedUserId", lastUserId).commit();
-
+                    openScale.selectScaleUser(lastUserId);
                     openScale.updateScaleData();
 
                     Intent returnIntent = new Intent();
@@ -325,13 +323,10 @@ public class UserSettingsActivity extends Activity {
                         scaleUser.setId(id);
                         openScale.updateScaleUser(scaleUser);
                     } else {
-                        openScale.addScaleUser(scaleUser);
-
-                        id = openScale.getScaleUserList().get(openScale.getScaleUserList().size() - 1).getId();
+                        id = openScale.addScaleUser(scaleUser);
                     }
 
-                    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-                    prefs.edit().putInt("selectedUserId", id).commit();
+                    openScale.selectScaleUser(id);
 
                     openScale.updateScaleData();
 
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/fragments/OverviewFragment.java b/android_app/app/src/main/java/com/health/openscale/gui/fragments/OverviewFragment.java
index 5acb9111..8896d292 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/fragments/OverviewFragment.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/fragments/OverviewFragment.java
@@ -476,13 +476,13 @@ public class OverviewFragment extends Fragment implements FragmentUpdateListener
              if (parent.getChildCount() > 0) {
                  ((TextView) parent.getChildAt(0)).setTextColor(Color.GRAY);
 
-                 List<ScaleUser> scaleUserList = OpenScale.getInstance(getContext()).getScaleUserList();
+                 OpenScale openScale = OpenScale.getInstance(getContext());
 
+                 List<ScaleUser> scaleUserList = openScale.getScaleUserList();
                  ScaleUser scaleUser = scaleUserList.get(position);
 
-                 SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
-                 prefs.edit().putInt("selectedUserId", scaleUser.getId()).commit();
-                 OpenScale.getInstance(getContext()).updateScaleData();
+                 openScale.selectScaleUser(scaleUser.getId());
+                 openScale.updateScaleData();
              }
         }
 
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/fragments/TableFragment.java b/android_app/app/src/main/java/com/health/openscale/gui/fragments/TableFragment.java
index c95d586c..d022678f 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/fragments/TableFragment.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/fragments/TableFragment.java
@@ -263,8 +263,7 @@ public class TableFragment extends Fragment implements FragmentUpdateListener {
         @Override
         public void onClick(View v) {
 
-            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(v.getContext());
-            int selectedUserId  = prefs.getInt("selectedUserId", -1);
+            int selectedUserId = OpenScale.getInstance(getContext()).getSelectedScaleUserId();
 
             if (selectedUserId == -1)
             {
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/preferences/BackupPreferences.java b/android_app/app/src/main/java/com/health/openscale/gui/preferences/BackupPreferences.java
index 3a852b2e..82b4fda6 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/preferences/BackupPreferences.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/preferences/BackupPreferences.java
@@ -125,8 +125,7 @@ public class BackupPreferences extends PreferenceFragment {
             List<ScaleUser> scaleUserList = openScale.getScaleUserList();
 
             if (!scaleUserList.isEmpty()) {
-                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity().getApplicationContext());
-                prefs.edit().putInt("selectedUserId", scaleUserList.get(0).getId()).commit();
+                openScale.selectScaleUser(scaleUserList.get(0).getId());
                 openScale.updateScaleData();
             }
 
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/preferences/MeasurementPreferences.java b/android_app/app/src/main/java/com/health/openscale/gui/preferences/MeasurementPreferences.java
index 64aff159..fe195dd4 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/preferences/MeasurementPreferences.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/preferences/MeasurementPreferences.java
@@ -247,10 +247,10 @@ public class MeasurementPreferences extends PreferenceFragment implements Shared
 
             deleteAllDialog.setPositiveButton(getResources().getString(R.string.label_yes), new DialogInterface.OnClickListener() {
                 public void onClick(DialogInterface dialog, int id) {
-                    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity().getApplicationContext());
-                    int selectedUserId  = prefs.getInt("selectedUserId", -1);
+                    OpenScale openScale = OpenScale.getInstance(getActivity().getApplicationContext());
+                    int selectedUserId = openScale.getSelectedScaleUserId();
 
-                    OpenScale.getInstance(getActivity().getApplicationContext()).clearScaleData(selectedUserId);
+                    openScale.clearScaleData(selectedUserId);
 
                     Toast.makeText(getActivity().getApplicationContext(), getResources().getString(R.string.info_data_all_deleted), Toast.LENGTH_SHORT).show();
                 }
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/preferences/UsersPreferences.java b/android_app/app/src/main/java/com/health/openscale/gui/preferences/UsersPreferences.java
index 0e5bc1af..1fdfa944 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/preferences/UsersPreferences.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/preferences/UsersPreferences.java
@@ -41,15 +41,13 @@ public class UsersPreferences extends PreferenceFragment {
         updateUserPreferences();
     }
 
-    private void updateUserPreferences()
-    {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity().getApplicationContext());
-        int selectedUserId  = prefs.getInt("selectedUserId", -1);
+    private void updateUserPreferences() {
+        OpenScale openScale = OpenScale.getInstance(getActivity().getApplicationContext());
+
+        int selectedUserId = openScale.getSelectedScaleUserId();
 
         getPreferenceScreen().removeAll();
 
-        OpenScale openScale = OpenScale.getInstance(getActivity().getApplicationContext());
-
         List<ScaleUser> scaleUserList = openScale.getScaleUserList();
 
         for (ScaleUser scaleUser : scaleUserList)