Initial implementation of loading only 25 rows from the message list

from SQLite at once. The hope is that this will improve perceived
performance on large folders by starting message display sooner.

In the case of a background sync while we're loading, we _may_ end up
doing more work than necessary, since we implement paging by "date
received"

src/com/fsck/k9/mail/store/LocalStore.java

@@ -1264,8 +1264,14 @@ public class LocalStore extends Store implements Serializable
             open(OpenMode.READ_WRITE);
             ArrayList<LocalMessage> messages = new ArrayList<LocalMessage>();
             Cursor cursor = null;
+            int totalSeen = 0;
+            int i;
             try
             {
+
+                while (true)
+                {
+
                 // pull out messages most recent first, since that's what the default sort is
                 cursor = mDb.rawQuery(
                              "SELECT subject, sender_list, date, uid, flags, id, to_list, cc_list, "
@@ -1273,14 +1279,14 @@ public class LocalStore extends Store implements Serializable
                              + "FROM messages "
                              + "WHERE "
                              + (includeDeleted ? "" : "deleted = 0 AND ")
-                             + " folder_id = ? ORDER BY date DESC"
+                             + " folder_id = ? ORDER BY date DESC LIMIT 25 OFFSET "+ totalSeen
                              , new String[]
                              {
                                  Long.toString(mFolderId)
                              });
 
 
-                int i = 0;
+                i = 0;
                 ArrayList<LocalMessage> messagesForHeaders = new ArrayList<LocalMessage>();
                 while (cursor.moveToNext())
                 {
@@ -1294,10 +1300,20 @@ public class LocalStore extends Store implements Serializable
                     }
                     i++;
                 }
-                if (listener != null)
-                {
-                    listener.messagesFinished(i);
+                totalSeen += i;
+                if ( i == 0 ) {
+                    break;
                 }
+                else
+                {
+                    cursor.close();
+                }
+            }
+
+            if (listener != null)
+            {
+                    listener.messagesFinished(totalSeen);
+            }
             }
             finally
             {
@@ -1599,6 +1615,8 @@ public class LocalStore extends Store implements Serializable
             }
         }
 
+
+
         private void saveHeaders(long id, MimeMessage message)
         {
             deleteHeaders(id);
@@ -2042,6 +2060,7 @@ public class LocalStore extends Store implements Serializable
         private int mAttachmentCount;
         private String mSubject;
 
+
         private boolean mHeadersLoaded = false;
         private boolean mMessageDirty = false;