title: How do I update a placeholder image with an async image?
body: <p>I'm using a manager class to either pull images from a cache or make a network request. I'm using a placeholder image. What's the best way to replace that placeholder image when the proper image is retrieved?</p>
  
  <pre><code>final ItemManager _manager;
  final Item _item;
  var _itemImage =
    new Image.asset('assets/images/icons/ic_placeholder.png');
  
  @override
  Widget build(BuildContext context) {
    _loadImage();
    return new Container(
      child: _itemImage,
    );
  }
  
  _loadImage() async {
    var file = await _manager.itemImageForImageUrl(_item.imageUrl);
    _stickerImage = new Image.file(file);
  }
  </code></pre>