Add caching for loaded tiles in TileLayer to improve performance and …

…reduce redundant tile loading. The cached tiles are stored in a Map where the key is the tile coordinates (x:y:z) and the value is the tile image as a byte list. This allows for quick retrieval of already loaded tiles, avoiding unnecessary network requests. The caching logic is implemented in the `_TileLayerState` class using a `Map<String, Uint8List>` called `_cachedTiles`. Each time a tile is loaded, it is added to the cache using its coordinates as the key. When a tile is requested, the cache is checked first before initiating a new load. This change improves the efficiency of the TileLayer component and reducing requests.

lib/src/layer/tile_layer/tile_layer.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 import 'dart:math';
+import 'dart:ui';
 
 import 'package:collection/collection.dart' show MapEquality;
 import 'package:flutter/foundation.dart';
@@ -330,6 +331,9 @@ class TileLayer extends StatefulWidget {
 class _TileLayerState extends State<TileLayer> with TickerProviderStateMixin {
  bool _initializedFromMapCamera = false;
 
+ ///Saves already loaded tiles in Map where key is (x:y:z) and value is tile image as bytes list
+ final Map<String, Uint8List> _cachedTiles = {};
+
  final _tileImageManager = TileImageManager();
  late TileBounds _tileBounds;
  late var _tileRangeCalculator =
@@ -633,28 +637,53 @@ class _TileLayerState extends State<TileLayer> with TickerProviderStateMixin {
  }) {
  final tileZoom = tileLoadRange.zoom;
  final expandedTileLoadRange = tileLoadRange.expand(widget.panBuffer);
-
- // Build the queue of tiles to load. Marks all tiles with valid coordinates
- // in the tileLoadRange as current.
  final tileBoundsAtZoom = _tileBounds.atZoom(tileZoom);
  final tilesToLoad = _tileImageManager.createMissingTiles(
- expandedTileLoadRange,
- tileBoundsAtZoom,
- createTile: (coordinates) => _createTileImage(
+ expandedTileLoadRange, tileBoundsAtZoom, createTile: (coordinates) {
+ final String key = '${coordinates.x}:${coordinates.y}:${coordinates.z}';
+ if (_cachedTiles.containsKey(key)) {
+ return TileImage(
+ vsync: this,
+ coordinates: coordinates,
+ imageProvider: MemoryImage(_cachedTiles[key]!),
+ onLoadError: _onTileLoadError,
+ onLoadComplete: (coordinates) {
+ if (pruneAfterLoad) _pruneIfAllTilesLoaded(coordinates);
+ },
+ tileDisplay: widget.tileDisplay,
+ errorImage: widget.errorImage,
+ cancelLoading: Completer<void>(),
+ );
+ }
+ final TileImage img = _createTileImage(
  coordinates: coordinates,
  tileBoundsAtZoom: tileBoundsAtZoom,
  pruneAfterLoad: pruneAfterLoad,
- ),
- );
+ );
+
+ img.imageProvider.resolve(ImageConfiguration()).addListener(
+ ImageStreamListener((ImageInfo info, bool _) async {
+ final ByteData? byteData =
+ await info.image.toByteData(format: ImageByteFormat.png);
+
+ //Currently workaround to skip adding tiles that are not loaded fully.
+ //Looks like was adding record to map even if loading was canceled resulting in empty tiles.
+ if (byteData!.lengthInBytes <= 97) {
+ return;
+ }
+ _cachedTiles[key] = byteData.buffer.asUint8List();
+ }),
+ );
+
+ return img;
+ });
 
- // Re-order the tiles by their distance to the center of the range.
  final tileCenter = expandedTileLoadRange.center;
  tilesToLoad.sort(
  (a, b) => _distanceSq(a.coordinates, tileCenter)
  .compareTo(_distanceSq(b.coordinates, tileCenter)),
  );
 
- // Create the new Tiles.
  for (final tile in tilesToLoad) {
  tile.load();
  }