Enable icon caching (#1837)

lib/pages/app.dart

@@ -248,7 +248,8 @@ class _AppPageState extends State<AppPage> {
           children: [
             const SizedBox(height: 20),
             FutureBuilder(
-                future: appsProvider.updateAppIcon(app?.app.id),
+                future:
+                    appsProvider.updateAppIcon(app?.app.id, ignoreCache: true),
                 builder: (ctx, val) {
                   return app?.icon != null
                       ? Row(

lib/pages/apps.dart

@@ -416,6 +416,8 @@ class AppsPageState extends State<AppsPage> {
                 ? Image.memory(
                     listedApps[appIndex].icon!,
                     gaplessPlayback: true,
+                    opacity: AlwaysStoppedAnimation(
+                        listedApps[appIndex].installedInfo == null ? 0.6 : 1),
                   )
                 : Row(
                     mainAxisSize: MainAxisSize.min,

lib/providers/apps_provider.dart

@@ -375,6 +375,7 @@ class AppsProvider with ChangeNotifier {
   late Stream<FGBGType>? foregroundStream;
   late StreamSubscription<FGBGType>? foregroundSubscription;
   late Directory APKDir;
+  late Directory iconsCacheDir;
   late SettingsProvider settingsProvider = SettingsProvider();
 
   Iterable<AppInMemory> getAppValues() => apps.values.map((a) => a.deepCopy());
@@ -393,12 +394,21 @@ class AppsProvider with ChangeNotifier {
       var cacheDirs = await getExternalCacheDirectories();
       if (cacheDirs?.isNotEmpty ?? false) {
         APKDir = cacheDirs!.first;
+        iconsCacheDir = Directory('${cacheDirs.first.path}/icons');
+        if (!iconsCacheDir.existsSync()) {
+          iconsCacheDir.createSync();
+        }
       } else {
         APKDir =
             Directory('${(await getExternalStorageDirectory())!.path}/apks');
         if (!APKDir.existsSync()) {
           APKDir.createSync();
         }
+        iconsCacheDir =
+            Directory('${(await getExternalStorageDirectory())!.path}/icons');
+        if (!iconsCacheDir.existsSync()) {
+          iconsCacheDir.createSync();
+        }
       }
       if (!isBg) {
         // Load Apps into memory (in background processes, this is done later instead of in the constructor)
@@ -1297,10 +1307,16 @@ class AppsProvider with ChangeNotifier {
     notifyListeners();
   }
 
-  Future<void> updateAppIcon(String? appId) async {
+  Future<void> updateAppIcon(String? appId, {bool ignoreCache = false}) async {
     if (apps[appId]?.icon == null) {
-      var icon =
-          (await apps[appId]?.installedInfo?.applicationInfo?.getAppIcon());
+      var cachedIcon = File('${iconsCacheDir.path}/$appId.png');
+      var alreadyCached = cachedIcon.existsSync() && !ignoreCache;
+      var icon = alreadyCached
+          ? (await cachedIcon.readAsBytes())
+          : (await apps[appId]?.installedInfo?.applicationInfo?.getAppIcon());
+      if (icon != null && !alreadyCached) {
+        cachedIcon.writeAsBytes(icon.toList());
+      }
       if (icon != null) {
         apps.update(
             apps[appId]!.app.id,
@@ -1351,6 +1367,10 @@ class AppsProvider with ChangeNotifier {
       if (file.existsSync()) {
         file.deleteSync(recursive: true);
       }
+      File iconFile = File('$iconsCacheDir/$appId.png');
+      if (iconFile.existsSync()) {
+        iconFile.deleteSync(recursive: true);
+      }
       apkFiles
           .where(
               (element) => element.path.split('/').last.startsWith('$appId-'))