refactoring: improve performance of GPX export

* load batches of caches instead of single caches
* do not load all caches to avoid huge memory usage

1 files changed, 88 insertions, 58 deletions

diff --git a/main/src/cgeo/geocaching/export/GpxExport.java b/main/src/cgeo/geocaching/export/GpxExport.java
index 36c8ca7..19b8518 100644
--- a/main/src/cgeo/geocaching/export/GpxExport.java
+++ b/main/src/cgeo/geocaching/export/GpxExport.java
@@ -38,8 +38,11 @@ import java.io.IOException;
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Date;
+import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
+import java.util.Set;
 
 class GpxExport extends AbstractExport {
     private static final SimpleDateFormat dateFormatZ = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
@@ -47,6 +50,11 @@ class GpxExport extends AbstractExport {
     public static final String PREFIX_GPX = "http://www.topografix.com/GPX/1/0";
     public static final String PREFIX_GROUNDSPEAK = "http://www.groundspeak.com/cache/1/0";
 
+    /**
+     * During the export, only this number of geocaches is fully loaded into memory.
+     */
+    public static final int CACHES_PER_BATCH = 100;
+
     protected GpxExport() {
         super(getString(R.string.export_gpx));
     }
@@ -98,8 +106,9 @@ class GpxExport extends AbstractExport {
     }
 
     private class ExportTask extends AsyncTaskWithProgress<Void, File> {
-        private final List<Geocache> caches;
+        private final Set<String> allGeocodes = new HashSet<String>();
         private final Activity activity;
+        private int countExported = 0;
 
         /**
          * Instantiates and configures the task for exporting field notes.
@@ -111,7 +120,11 @@ class GpxExport extends AbstractExport {
          */
         public ExportTask(final List<Geocache> caches, final Activity activity) {
             super(activity, caches.size(), getProgressTitle(), cgeoapplication.getInstance().getResources().getQuantityString(R.plurals.cache_counts, caches.size(), caches.size()));
-            this.caches = caches;
+
+            // get rid of the (half loaded) caches, we will reload them as full caches during the export
+            for (Geocache geocache : caches) {
+                allGeocodes.add(geocache.getGeocode());
+            }
             this.activity = activity;
         }
 
@@ -144,68 +157,24 @@ class GpxExport extends AbstractExport {
                         PREFIX_GPX + " http://www.topografix.com/GPX/1/0/gpx.xsd " +
                                 PREFIX_GROUNDSPEAK + " http://www.groundspeak.com/cache/1/0/1/cache.xsd");
 
-                for (int i = 0; i < caches.size(); i++) {
-                    final Geocache cache = cgData.loadCache(caches.get(i).getGeocode(), LoadFlags.LOAD_ALL_DB_ONLY);
+                // Split the overall set of geocodes into small chunks. That is a compromise between memory efficiency (because
+                // we don't load all caches fully into memory) and speed (because we don't query each cache separately).
 
-                    gpx.startTag(PREFIX_GPX, "wpt");
-                    gpx.attribute("", "lat", Double.toString(cache.getCoords().getLatitude()));
-                    gpx.attribute("", "lon", Double.toString(cache.getCoords().getLongitude()));
-
-                    final Date hiddenDate = cache.getHiddenDate();
-                    if (hiddenDate != null) {
-                        XmlUtils.simpleText(gpx, PREFIX_GPX, "time", dateFormatZ.format(hiddenDate));
+                while (!allGeocodes.isEmpty()) {
+                    int cachesInBatch = 0;
+                    HashSet<String> geocodesOfBatch = new HashSet<String>(CACHES_PER_BATCH);
+                    for (Iterator<String> iterator = allGeocodes.iterator(); iterator.hasNext() && cachesInBatch < CACHES_PER_BATCH;) {
+                        final String geocode = iterator.next();
+                        geocodesOfBatch.add(geocode);
+                        cachesInBatch++;
                     }
-
-                    XmlUtils.multipleTexts(gpx, PREFIX_GPX,
-                            "name", cache.getGeocode(),
-                            "desc", cache.getName(),
-                            "url", cache.getUrl(),
-                            "urlname", cache.getName(),
-                            "sym", cache.isFound() ? "Geocache Found" : "Geocache",
-                            "type", "Geocache|" + cache.getType().pattern);
-
-                    gpx.startTag(PREFIX_GROUNDSPEAK, "cache");
-                    gpx.attribute("", "id", cache.getCacheId());
-                    gpx.attribute("", "available", !cache.isDisabled() ? "True" : "False");
-                    gpx.attribute("", "archives", cache.isArchived() ? "True" : "False");
-
-                    XmlUtils.multipleTexts(gpx, PREFIX_GROUNDSPEAK,
-                            "name", cache.getName(),
-                            "placed_by", cache.getOwnerDisplayName(),
-                            "owner", cache.getOwnerUserId(),
-                            "type", cache.getType().pattern,
-                            "container", cache.getSize().id,
-                            "difficulty", Float.toString(cache.getDifficulty()),
-                            "terrain", Float.toString(cache.getTerrain()),
-                            "country", cache.getLocation(),
-                            "state", "",
-                            "encoded_hints", cache.getHint());
-
-                    writeAttributes(gpx, cache);
-
-                    gpx.startTag(PREFIX_GROUNDSPEAK, "short_description");
-                    gpx.attribute("", "html", BaseUtils.containsHtml(cache.getShortDescription()) ? "True" : "False");
-                    gpx.text(cache.getShortDescription());
-                    gpx.endTag(PREFIX_GROUNDSPEAK, "short_description");
-
-                    gpx.startTag(PREFIX_GROUNDSPEAK, "long_description");
-                    gpx.attribute("", "html", BaseUtils.containsHtml(cache.getDescription()) ? "True" : "False");
-                    gpx.text(cache.getDescription());
-                    gpx.endTag(PREFIX_GROUNDSPEAK, "long_description");
-
-                    writeLogs(gpx, cache);
-
-                    gpx.endTag(PREFIX_GROUNDSPEAK, "cache");
-                    gpx.endTag(PREFIX_GPX, "wpt");
-
-                    writeWaypoints(gpx, cache);
-
-                    publishProgress(i + 1);
+                    allGeocodes.removeAll(geocodesOfBatch);
+                    exportBatch(gpx, geocodesOfBatch);
                 }
 
                 gpx.endTag(PREFIX_GPX, "gpx");
                 gpx.endDocument();
-            } catch (final IOException e) {
+            } catch (final Exception e) {
                 Log.e("GpxExport.ExportTask export", e);
 
                 if (writer != null) {
@@ -226,6 +195,67 @@ class GpxExport extends AbstractExport {
             return exportFile;
         }
 
+        private void exportBatch(final XmlSerializer gpx, HashSet<String> geocodesOfBatch) throws IOException {
+            Set<Geocache> caches = cgData.loadCaches(geocodesOfBatch, LoadFlags.LOAD_ALL_DB_ONLY);
+            for (Geocache cache : caches) {
+                gpx.startTag(PREFIX_GPX, "wpt");
+                gpx.attribute("", "lat", Double.toString(cache.getCoords().getLatitude()));
+                gpx.attribute("", "lon", Double.toString(cache.getCoords().getLongitude()));
+
+                final Date hiddenDate = cache.getHiddenDate();
+                if (hiddenDate != null) {
+                    XmlUtils.simpleText(gpx, PREFIX_GPX, "time", dateFormatZ.format(hiddenDate));
+                }
+
+                XmlUtils.multipleTexts(gpx, PREFIX_GPX,
+                        "name", cache.getGeocode(),
+                        "desc", cache.getName(),
+                        "url", cache.getUrl(),
+                        "urlname", cache.getName(),
+                        "sym", cache.isFound() ? "Geocache Found" : "Geocache",
+                        "type", "Geocache|" + cache.getType().pattern);
+
+                gpx.startTag(PREFIX_GROUNDSPEAK, "cache");
+                gpx.attribute("", "id", cache.getCacheId());
+                gpx.attribute("", "available", !cache.isDisabled() ? "True" : "False");
+                gpx.attribute("", "archives", cache.isArchived() ? "True" : "False");
+
+                XmlUtils.multipleTexts(gpx, PREFIX_GROUNDSPEAK,
+                        "name", cache.getName(),
+                        "placed_by", cache.getOwnerDisplayName(),
+                        "owner", cache.getOwnerUserId(),
+                        "type", cache.getType().pattern,
+                        "container", cache.getSize().id,
+                        "difficulty", Float.toString(cache.getDifficulty()),
+                        "terrain", Float.toString(cache.getTerrain()),
+                        "country", cache.getLocation(),
+                        "state", "",
+                        "encoded_hints", cache.getHint());
+
+                writeAttributes(gpx, cache);
+
+                gpx.startTag(PREFIX_GROUNDSPEAK, "short_description");
+                gpx.attribute("", "html", BaseUtils.containsHtml(cache.getShortDescription()) ? "True" : "False");
+                gpx.text(cache.getShortDescription());
+                gpx.endTag(PREFIX_GROUNDSPEAK, "short_description");
+
+                gpx.startTag(PREFIX_GROUNDSPEAK, "long_description");
+                gpx.attribute("", "html", BaseUtils.containsHtml(cache.getDescription()) ? "True" : "False");
+                gpx.text(cache.getDescription());
+                gpx.endTag(PREFIX_GROUNDSPEAK, "long_description");
+
+                writeLogs(gpx, cache);
+
+                gpx.endTag(PREFIX_GROUNDSPEAK, "cache");
+                gpx.endTag(PREFIX_GPX, "wpt");
+
+                writeWaypoints(gpx, cache);
+
+                countExported++;
+                publishProgress(countExported);
+            }
+        }
+
         private void writeWaypoints(final XmlSerializer gpx, final Geocache cache) throws IOException {
             List<Waypoint> waypoints = cache.getWaypoints();
             List<Waypoint> ownWaypoints = new ArrayList<Waypoint>(waypoints.size());