improve handling of file updates

src/ch/blinkenlights/android/medialibrary/MediaMetadataExtractor.java

@@ -76,6 +76,14 @@ public class MediaMetadataExtractor extends HashMap<String, ArrayList<String>> {
 		return result;
 	}
 
+	/**
+	 * Returns true if this file contains any (interesting) tags
+	 * @return true if file is considered to be tagged
+	 */
+	public boolean isTagged() {
+		return (containsKey(TITLE) || containsKey(ALBUM) || containsKey(ARTIST));
+	}
+
 	/**
 	 * Attempts to populate this instance with tags found in given path
 	 *

src/ch/blinkenlights/android/medialibrary/MediaScanner.java

@@ -157,26 +157,28 @@ public class MediaScanner implements Handler.Callback {
 		if (isBlacklisted(file))
 			return false;
 
-
 		long dbEntryMtime = mBackend.getSongMtime(songId) * 1000; // this is in unixtime -> convert to 'ms'
 		long fileMtime = file.lastModified();
-		boolean needsPurge = false;
+		boolean needsInsert = true;
+		boolean needsCleanup = false;
 
 		if (dbEntryMtime >= fileMtime) {
-			Log.v("VanillaMusic", "Skipping already known song with id "+songId);
-			return false;
+			return false; // on-disk mtime is older than db mtime -> nothing to do
 		}
 
 		if (dbEntryMtime != 0) {
+			// file on disk is newer: delete old entry and re-insert it
 			// fixme: drops play counts :-(
 			mBackend.delete(MediaLibrary.TABLE_SONGS, MediaLibrary.SongColumns._ID+"="+songId, null);
-			needsPurge = true;
+			needsCleanup = true;
 		}
 
 		MediaMetadataExtractor tags = new MediaMetadataExtractor(path);
-		if (tags.isEmpty())
-			return false; // file does not contain audio data
+		if (tags.isTagged() == false) {
+			needsInsert = false; // does not have any useable metadata: wont insert even if it is a playable file
+		}
 
+		if (needsInsert) {
 			// Get tags which always must be set
 			String title = tags.getFirst(MediaMetadataExtractor.TITLE);
 			if (title == null)
@@ -260,11 +262,14 @@ public class MediaScanner implements Handler.Callback {
 					mBackend.insert(MediaLibrary.TABLE_GENRES_SONGS, null, v);
 				}
 			}
-		if (needsPurge)
+		} // end if (needsInsert)
+
+
+		if (needsCleanup)
 			mBackend.cleanOrphanedEntries();
 
 		Log.v("VanillaMusic", "MediaScanner: inserted "+path);
-		return true;
+		return (needsInsert || needsCleanup);
 	}
 
 }