increase performance while switching between data entries

android_app/app/src/main/java/com/health/openscale/core/OpenScale.java

@@ -161,9 +161,9 @@ public class OpenScale {
 	}
 
 
-    public ScaleData getScaleData(long id)
+    public ScaleData[] getTupleScaleData(long id)
     {
-        return scaleDB.getDataEntry(id);
+        return scaleDB.getTupleDataEntry(id);
     }
 
 	public int addScaleData(ScaleData scaleData) {

android_app/app/src/main/java/com/health/openscale/core/database/ScaleDatabase.java

@@ -172,25 +172,72 @@ public class ScaleDatabase extends SQLiteOpenHelper {
         dbWrite.update(TABLE_NAME, values, COLUMN_NAME_ID + "=" + id, null);
     }
 
-    public ScaleData getDataEntry(long id)
+    public ScaleData[] getTupleDataEntry(long id)
     {
-        Cursor cursorScaleDB = dbRead.query(
+        Cursor cursorScaleDB;
+
+        ScaleData[] tupleScaleData = new ScaleData[3];
+
+        // selected scale data entry
+        cursorScaleDB = dbRead.query(
                 TABLE_NAME, 	// The table to query
                 projection, 	// The columns to return
                 COLUMN_NAME_ID + "=?", 			// The columns for the WHERE clause
                 new String[] {Long.toString(id)}, 			// The values for the WHERE clause
                 null, 			// don't group the rows
                 null,			// don't filter by row groups
-                null  		// The sort order
+                null,  		// The sort order
+                "1"         // Limit
         );
 
+        if (cursorScaleDB.getCount() == 1) {
             cursorScaleDB.moveToFirst();
+            tupleScaleData[1] = readAtCursor(cursorScaleDB);
+        } else {
+            tupleScaleData[1] = null;
+        }
 
-        ScaleData scaleData = readAtCursor(cursorScaleDB);
+        // previous scale entry
+        cursorScaleDB = dbRead.query(
+                TABLE_NAME, 	// The table to query
+                projection, 	// The columns to return
+                COLUMN_NAME_DATE_TIME + "<? AND " + COLUMN_NAME_ENABLE + "=1", 			// The columns for the WHERE clause
+                new String[] {formatDateTime.format(tupleScaleData[1].getDateTime())}, 			// The values for the WHERE clause
+                null, 			// don't group the rows
+                null,			// don't filter by row groups
+                COLUMN_NAME_DATE_TIME + " DESC",  	// The sort order
+                "1"             // Limit
+        );
+
+        if (cursorScaleDB.getCount() == 1) {
+            cursorScaleDB.moveToFirst();
+            tupleScaleData[0] = readAtCursor(cursorScaleDB);
+        } else {
+            tupleScaleData[0] = null;
+        }
 
         cursorScaleDB.close();
 
-        return scaleData;
+        // next scale data entry
+        cursorScaleDB = dbRead.query(
+                TABLE_NAME, 	// The table to query
+                projection, 	// The columns to return
+                COLUMN_NAME_DATE_TIME + ">? AND " + COLUMN_NAME_ENABLE + "=1", 			// The columns for the WHERE clause
+                new String[] {formatDateTime.format(tupleScaleData[1].getDateTime())}, 			// The values for the WHERE clause
+                null, 			// don't group the rows
+                null,			// don't filter by row groups
+                COLUMN_NAME_DATE_TIME, // The sort order
+                "1"             // Limit
+        );
+
+        if (cursorScaleDB.getCount() == 1) {
+            cursorScaleDB.moveToFirst();
+            tupleScaleData[2] = readAtCursor(cursorScaleDB);
+        } else {
+            tupleScaleData[2] = null;
+        }
+
+        return tupleScaleData;
     }
 
     public void deleteEntry(long id) {

android_app/app/src/main/java/com/health/openscale/gui/activities/DataEntryActivity.java

@@ -52,7 +52,6 @@ import java.text.DateFormat;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
-import java.util.ListIterator;
 
 import lecho.lib.hellocharts.util.ChartUtils;
 
@@ -184,30 +183,21 @@ public class DataEntryActivity extends Activity {
 
             OpenScale openScale = OpenScale.getInstance(context);
 
-            ScaleData selectedScaleData = openScale.getScaleData(id);
+            ScaleData[] tupleScaleData = openScale.getTupleScaleData(id);
+            ScaleData prevScaleData = tupleScaleData[0];
+            ScaleData selectedScaleData = tupleScaleData[1];
+
+            if (prevScaleData == null) {
+                prevScaleData = new ScaleData();
+            }
 
             txtDataNr.setText(DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.SHORT).format(selectedScaleData.getDateTime()));
 
-            ArrayList<ScaleData> scaleDataList = OpenScale.getInstance(context).getScaleDataList();
-            ListIterator<ScaleData> scaleDataIterator = scaleDataList.listIterator();
-
-            ScaleData lastData = new ScaleData();
-
-            while(scaleDataIterator.hasNext()) {
-                ScaleData scaleData = scaleDataIterator.next();
-
-                if (scaleData.getId() == id) {
-                    if (scaleDataIterator.hasNext()) {
-                        lastData = scaleDataIterator.next();
-                    }
-                }
-            }
-
             // show selected scale data
             for (MeasurementView measuremt : dataEntryMeasurements) {
                 measuremt.setExpand(prefs.getBoolean(String.valueOf(expandButton.getId()), false));
                 measuremt.updateValue(selectedScaleData);
-                measuremt.updateDiff(selectedScaleData, lastData);
+                measuremt.updateDiff(selectedScaleData, prevScaleData);
             }
 
             return;
@@ -298,26 +288,14 @@ public class DataEntryActivity extends Activity {
     }
 
     private boolean moveLeft() {
-        ArrayList<ScaleData> scaleDataList = OpenScale.getInstance(getApplicationContext()).getScaleDataList();
+        ScaleData[] tupleScaleData = OpenScale.getInstance(getApplicationContext()).getTupleScaleData(id);
+        ScaleData prevScaleData = tupleScaleData[0];
 
-        ListIterator<ScaleData> scaleDataIterator = scaleDataList.listIterator();
+        if (prevScaleData != null) {
-
-        while(scaleDataIterator.hasNext())
-        {
-            ScaleData scaleData = scaleDataIterator.next();
-
-            if (scaleData.getId() == id)
-            {
-                if (scaleDataIterator.hasNext()) {
             saveScaleData();
-                    getIntent().putExtra("id",scaleDataIterator.next().getId() );
+            getIntent().putExtra("id", prevScaleData.getId());
             updateOnView();
             return true;
-                } else {
-                    return false;
-                }
-
-            }
         }
 
         return false;
@@ -325,25 +303,14 @@ public class DataEntryActivity extends Activity {
 
     private boolean moveRight()
     {
-        ArrayList<ScaleData> scaleDataList = OpenScale.getInstance(getApplicationContext()).getScaleDataList();
+        ScaleData[] tupleScaleData = OpenScale.getInstance(getApplicationContext()).getTupleScaleData(id);
+        ScaleData nextScaleData = tupleScaleData[2];
 
-        ListIterator<ScaleData> scaleDataIterator = scaleDataList.listIterator(scaleDataList.size());
+        if (nextScaleData != null) {
-
-        while(scaleDataIterator.hasPrevious())
-        {
-            ScaleData scaleData = scaleDataIterator.previous();
-
-            if (scaleData.getId() == id)
-            {
-                if (scaleDataIterator.hasPrevious()) {
             saveScaleData();
-                    getIntent().putExtra("id", scaleDataIterator.previous().getId());
+            getIntent().putExtra("id", nextScaleData.getId());
             updateOnView();
             return true;
-                } else {
-                    return false;
-                }
-            }
         }
 
         return false;