added a new helper class that converts a track into GPX - see issue #14

app/src/main/java/org/y20k/trackbook/helpers/GpxHelper.java

@@ -0,0 +1,108 @@
+/**
+ * GpxHelper.java
+ * Implements the GpxHelper class
+ * A GpxHelper can convert Track object into a GPX string
+ *
+ * This file is part of
+ * TRACKBOOK - Movement Recorder for Android
+ *
+ * Copyright (c) 2016-17 - Y20K.org
+ * Licensed under the MIT-License
+ * http://opensource.org/licenses/MIT
+ *
+ * Trackbook uses osmdroid - OpenStreetMap-Tools for Android
+ * https://github.com/osmdroid/osmdroid
+ */
+
+package org.y20k.trackbook.helpers;
+
+import android.location.Location;
+
+import org.y20k.trackbook.core.Track;
+import org.y20k.trackbook.core.WayPoint;
+
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+
+/**
+ * GpxHelper class
+ */
+public class GpxHelper {
+
+    /* Define log tag */
+    private static final String LOG_TAG = GpxHelper.class.getSimpleName();
+
+
+    /* Main class variables */
+    private final Track mTrack;
+
+
+    /* Constructor */
+    public GpxHelper(Track track) {
+        mTrack = track;
+    }
+
+
+    /* Creates GPX formatted string */
+    public String createGpxString() {
+        String gpxString;
+
+        // add header
+        gpxString = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?>\n" +
+                    "<gpx version=\"1.1\" creator=\"Transistor App (Android)\">\n";
+
+        // add track
+        gpxString = gpxString + addTrack();
+
+        // add closing tag
+        gpxString = gpxString + "</gpx>\n";
+
+        // todo remove
+        LogHelper.v(LOG_TAG, "GPX output:\n" + gpxString);
+
+        return gpxString;
+    }
+
+
+    /* Creates Track */
+    private String addTrack() {
+        StringBuilder gpxTrack = new StringBuilder("");
+        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
+
+        // add opening route tag
+        gpxTrack.append("\t<rte>\n");
+
+        // add route point
+        for (WayPoint wayPoint:mTrack.getWayPoints()) {
+            // get location from waypoint
+            Location location = wayPoint.getLocation();
+
+            // add longitude and latitude
+            gpxTrack.append("\t\t<rtept lat=\"");
+            gpxTrack.append(location.getLatitude());
+            gpxTrack.append("\" lon=\"");
+            gpxTrack.append(location.getLongitude());
+            gpxTrack.append("\">\n");
+
+            // add time
+            gpxTrack.append("\t\t\t<time>");
+            gpxTrack.append(dateFormat.format(new Date(location.getTime())));
+            gpxTrack.append("</time>\n");
+
+            // add altitude
+            gpxTrack.append("\t\t\t<ele>");
+            gpxTrack.append(location.getAltitude());
+            gpxTrack.append("</ele>\n");
+
+            // add closing tag
+            gpxTrack.append("\t\t</rtept>\n");
+        }
+
+        // add closing route tag
+        gpxTrack.append("\t</rte>\n");
+
+        return gpxTrack.toString();
+    }
+
+}