neon: improve loading animation of NeonCachedImage

packages/neon/neon/lib/src/widgets/cached_image.dart

@@ -27,15 +27,43 @@ abstract class NeonCachedImage extends StatefulWidget {
 }
 
 class _NeonCachedImageState extends State<NeonCachedImage> {
-  late Future<File> future = widget.getImageFile();
+  Future<Uint8List> _readImage() async {
+    final file = await widget.getImageFile();
+    return file.readAsBytes();
+  }
+
+  late Future<Uint8List> _future = _readImage();
 
   @override
   Widget build(final BuildContext context) => Center(
-        child: FutureBuilder<File>(
+        child: FutureBuilder<Uint8List>(
-          future: future,
+          future: _future,
           builder: (final context, final fileSnapshot) {
-            if (fileSnapshot.hasData) {
+            if (!fileSnapshot.hasData) {
-              final content = fileSnapshot.requireData.readAsBytesSync();
+              return SizedBox(
+                width: widget.size?.width,
+                child: NeonLinearProgressIndicator(
+                  color: widget.iconColor,
+                ),
+              );
+            }
+
+            if (fileSnapshot.hasError) {
+              return NeonException(
+                fileSnapshot.error,
+                onRetry: () {
+                  setState(() {
+                    // ignore: discarded_futures
+                    _future = _readImage();
+                  });
+                },
+                onlyIcon: true,
+                iconSize: widget.size?.shortestSide,
+                color: widget.iconColor ?? Theme.of(context).colorScheme.error,
+              );
+            }
+
+            final content = fileSnapshot.requireData;
 
             try {
               // TODO: Is this safe enough?
@@ -59,27 +87,6 @@ class _NeonCachedImageState extends State<NeonCachedImage> {
               fit: widget.fit,
               gaplessPlayback: true,
             );
-            }
-            if (fileSnapshot.hasError) {
-              return NeonException(
-                fileSnapshot.error,
-                onRetry: () {
-                  setState(() {
-                    // ignore: discarded_futures
-                    future = widget.getImageFile();
-                  });
-                },
-                onlyIcon: true,
-                iconSize: widget.size?.shortestSide,
-                color: widget.iconColor ?? Theme.of(context).colorScheme.error,
-              );
-            }
-            return SizedBox(
-              width: widget.size?.width,
-              child: NeonLinearProgressIndicator(
-                color: widget.iconColor,
-              ),
-            );
           },
         ),
       );