fix #147

Author: 李卓原

README_CN.md

@@ -208,9 +208,7 @@ class _MyHomePageState extends State<MyHomePage> {
   @override
   Widget build(BuildContext context) {
     //设置适配尺寸 (填入设计稿中设备的屏幕尺寸) 此处假如设计稿是按iPhone6的尺寸设计的(iPhone6 750*1334)
-    ScreenUtil.init(width: 750, height: 1334, allowFontScaling: false);
-    ScreenUtil.init();
-    ScreenUtil.init(width: 750, height: 1334, allowFontScaling: false);
+    ScreenUtil.init(context, width: 750, height: 1334, allowFontScaling: false);
 
     return ExampleWidget(title: 'FlutterScreenUtil示例');
   }