Store URI within tracks

android/app/src/main/kotlin/de/johrpan/musicus/MainActivity.kt

@@ -44,6 +44,11 @@ class MainActivity : FlutterActivity() {
                 val treeUri = Uri.parse(call.argument<String>("treeUri"))
                 val id = call.argument<String>("id")!!
                 result.success(readFile(treeUri, id))
+            } else if (call.method == "getUriByName") {
+                val treeUri = Uri.parse(call.argument<String>("treeUri"))
+                val parentId = call.argument<String>("parentId")!!
+                val fileName = call.argument<String>("fileName")!!
+                result.success(getUriByName(treeUri, parentId, fileName).toString())
             } else if (call.method == "readFileByName") {
                 val treeUri = Uri.parse(call.argument<String>("treeUri"))
                 val parentId = call.argument<String>("parentId")!!

lib/music_library.dart

@@ -24,6 +24,8 @@ class Track {
   /// Which work parts of the recorded work are contained in this track.
   final List<int> partIds;
 
+  String uri;
+
   Track({
     this.fileName,
     this.index,
@@ -110,6 +112,10 @@ class MusicLibrary {
           final content = await Platform.readFile(treeUri, child.id);
           final musicusFile = MusicusFile.fromJson(jsonDecode(content));
           for (final track in musicusFile.tracks) {
+            final uri =
+                await Platform.getUriByName(treeUri, parentId, track.fileName);
+            track.uri = uri;
+
             if (tracks.containsKey(track.recordingId)) {
               tracks[track.recordingId].add(track);
             } else {
@@ -124,7 +130,7 @@ class MusicLibrary {
   }
 
   /// Add a list of new tracks to the music library.
-  /// 
+  ///
   /// They are stored in this instance and on disk in the directory denoted by
   /// [parentId].
   Future<void> addTracks(String parentId, List<Track> newTracks) async {
@@ -140,6 +146,10 @@ class MusicLibrary {
     }
 
     for (final track in newTracks) {
+      final uri =
+          await Platform.getUriByName(treeUri, parentId, track.fileName);
+      track.uri = uri;
+
       musicusFile.tracks.add(track);
 
       if (tracks.containsKey(track.recordingId)) {

lib/platform.dart

@@ -62,6 +62,22 @@ class Platform {
     );
   }
 
+  /// Get document URI by file name
+  ///
+  /// [treeId] is the base URI from the SAF, [parentId] is the document ID of
+  /// the parent directory.
+  static Future<String> getUriByName(
+      String treeUri, String parentId, String fileName) async {
+    return await _platform.invokeMethod(
+      'getUriByName',
+      {
+        'treeUri': treeUri,
+        'parentId': parentId,
+        'fileName': fileName,
+      },
+    );
+  }
+
   /// Read contents of file by name
   ///
   /// [treeId] is the base URI from the SAF, [parentId] is the document ID of