Refactoring assets loading on Flame

lib/sprite.dart

@@ -1,7 +1,5 @@
 import 'dart:ui';
 
-import 'dart:async';
-import 'flame.dart';
 import 'position.dart';
 import 'palette.dart';
 
@@ -11,67 +9,24 @@ class Sprite {
   Rect src;
 
   Sprite(
-    String fileName, {
-    double x = 0.0,
-    double y = 0.0,
-    double width,
-    double height,
-  }) {
-    Flame.images.load(fileName).then((img) {
-      width ??= img.width.toDouble();
-      height ??= img.height.toDouble();
-      image = img;
-      src = Rect.fromLTWH(x, y, width, height);
-    });
-  }
-
-  Sprite.fromImage(
     this.image, {
     double x = 0.0,
     double y = 0.0,
     double width,
     double height,
-  }) {
+  }) : assert(image != null, "image can't be null") {
     width ??= image.width.toDouble();
     height ??= image.height.toDouble();
     src = Rect.fromLTWH(x, y, width, height);
   }
 
-  static Future<Sprite> loadSprite(
-    String fileName, {
-    double x = 0.0,
-    double y = 0.0,
-    double width,
-    double height,
-  }) async {
-    final Image image = await Flame.images.load(fileName);
-    return Sprite.fromImage(
-      image,
-      x: x,
-      y: y,
-      width: width,
-      height: height,
-    );
-  }
-
-  bool loaded() {
-    return image != null && src != null;
-  }
-
   double get _imageWidth => image.width.toDouble();
 
   double get _imageHeight => image.height.toDouble();
 
-  Position get originalSize {
-    if (!loaded()) {
-      return null;
-    }
-    return Position(_imageWidth, _imageHeight);
-  }
+  Position get originalSize => Position(_imageWidth, _imageHeight);
 
-  Position get size {
-    return Position(src.width, src.height);
-  }
+  Position get size => Position(src.width, src.height);
 
   /// Renders this Sprite on the position [p], scaled by the [scale] factor provided.
   ///
@@ -80,18 +35,12 @@ class Sprite {
   /// If not loaded, does nothing.
   void renderScaled(Canvas canvas, Position p,
       {double scale = 1.0, Paint overridePaint}) {
-    if (!loaded()) {
-      return;
-    }
     renderPosition(canvas, p,
         size: size.times(scale), overridePaint: overridePaint);
   }
 
   void renderPosition(Canvas canvas, Position p,
       {Position size, Paint overridePaint}) {
-    if (!loaded()) {
-      return;
-    }
     size ??= this.size;
     renderRect(canvas, Position.rectFrom(p, size),
         overridePaint: overridePaint);
@@ -99,9 +48,6 @@ class Sprite {
 
   void render(Canvas canvas,
       {double width, double height, Paint overridePaint}) {
-    if (!loaded()) {
-      return;
-    }
     width ??= size.x;
     height ??= size.y;
     renderRect(canvas, Rect.fromLTWH(0.0, 0.0, width, height),
@@ -114,9 +60,6 @@ class Sprite {
   /// If the asset is not yet loaded, it does nothing.
   void renderCentered(Canvas canvas, Position p,
       {Position size, Paint overridePaint}) {
-    if (!loaded()) {
-      return;
-    }
     size ??= this.size;
     renderRect(canvas,
         Rect.fromLTWH(p.x - size.x / 2, p.y - size.y / 2, size.x, size.y),
@@ -124,9 +67,6 @@ class Sprite {
   }
 
   void renderRect(Canvas canvas, Rect dst, {Paint overridePaint}) {
-    if (!loaded()) {
-      return;
-    }
     canvas.drawImageRect(image, src, dst, overridePaint ?? paint);
   }
 }