flutter.002.AssetImage无法找到图片Unable to load asset

代码:

  Container(
    width: 60.0,
    height: 60.0,
    decoration: new BoxDecoration(
      border: new Border.all(width: 2.0, color: Colors.red),
      image: new DecorationImage(
          image: new ExactAssetImage('assets/images/bird.jpg'),
        fit: BoxFit.cover
      ),
    ),
  ),

配置文件如下:

flutter:
  assets:
    - assets/images/bird.jpg
    - assets/images/cat.jpg
    - assets/images/dog.jpg
    - assets/images/fish.jpg
    - assets/images/mouse.jpg
    - assets/images/wmouse.jpg

报错如下：

Unable to load asset: assets/images/bird.jpgImage provider: ExactAssetImage(name: "assets/bird.jpg", scale: 1.0, bundle: null)

按理说这个是按照官网的配置来写的，不应该出错，把AssetImagent改成ExactAssetImage，也没有什么用。

结果，发现，assets目录必须和项目根目录相同。这错误好无聊。