map: vector tile cache on external storage

android/app/src/main/kotlin/deckers/thibault/aves/channel/calls/StorageHandler.kt

@@ -29,6 +29,7 @@ class StorageHandler(private val context: Context) : MethodCallHandler {
         when (call.method) {
             "getDataUsage" -> ioScope.launch { safe(call, result, ::getDataUsage) }
             "getStorageVolumes" -> ioScope.launch { safe(call, result, ::getStorageVolumes) }
+            "getCacheDirectory" -> ioScope.launch { safe(call, result, ::getCacheDirectory) }
             "getUntrackedTrashPaths" -> ioScope.launch { safe(call, result, ::getUntrackedTrashPaths) }
             "getUntrackedVaultPaths" -> ioScope.launch { safe(call, result, ::getUntrackedVaultPaths) }
             "getVaultRoot" -> ioScope.launch { safe(call, result, ::getVaultRoot) }
@@ -122,6 +123,18 @@ class StorageHandler(private val context: Context) : MethodCallHandler {
         result.success(volumes)
     }
 
+    private fun getCacheDirectory(call: MethodCall, result: MethodChannel.Result) {
+        val external = call.argument<Boolean>("external")
+        if (external == null) {
+            result.error("getCacheDirectory-args", "missing arguments", null)
+            return
+        }
+
+        val dir = (if (external) context.externalCacheDir else context.cacheDir)
+        result.success(dir!!.path)
+    }
+
+
     private fun getUntrackedTrashPaths(call: MethodCall, result: MethodChannel.Result) {
         val knownPaths = call.argument<List<String>>("knownPaths")
         if (knownPaths == null) {

lib/services/storage_service.dart

@@ -12,6 +12,8 @@ abstract class StorageService {
 
   Future<Set<StorageVolume>> getStorageVolumes();
 
+  Future<String> getExternalCacheDirectory();
+
   Future<Set<String>> getUntrackedTrashPaths(Iterable<String> knownPaths);
 
   Future<Set<String>> getUntrackedVaultPaths(String vaultName, Iterable<String> knownPaths);
@@ -79,6 +81,19 @@ class PlatformStorageService implements StorageService {
     return {};
   }
 
+  @override
+  Future<String> getExternalCacheDirectory() async {
+    try {
+      final result = await _platform.invokeMethod('getCacheDirectory', <String, dynamic>{
+        'external': true,
+      });
+      return result as String;
+    } on PlatformException catch (e, stack) {
+      await reportService.recordError(e, stack);
+    }
+    return '';
+  }
+
   @override
   Future<Set<String>> getUntrackedTrashPaths(Iterable<String> knownPaths) async {
     try {

lib/widgets/common/map/leaflet/tile_layers.dart

@@ -1,4 +1,7 @@
+import 'dart:io';
+
 import 'package:aves/model/device.dart';
+import 'package:aves/services/common/services.dart';
 import 'package:aves/widgets/common/map/leaflet/vector_style_reader_extra.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_map/flutter_map.dart';
@@ -115,6 +118,10 @@ class _OsmLibertyLayerState extends State<OsmLibertyLayer> {
               sprites: style.sprites,
               // `vector` is higher quality and follows map orientation, but it is slower
               layerMode: VectorTileLayerMode.raster,
+              cacheFolder: () async {
+                final cacheRoot = await storageService.getExternalCacheDirectory();
+                return Directory(pContext.join(cacheRoot, 'map_vector_tiles'));
+              },
             );
           },
         );