title: flutter CachedNetworkImageProvider is not working
body: <pre><code>CircleAvatar(
                      radius: 40.0,
                      backgroundColor: Colors.blue,
                      backgroundImage: 
                          user.profileImageUrl.isEmpty 
                              ? AssetImage('assets/images/user.png') 
                              : CachedNetworkImageProvider(user.profileImageUrl),
                    ),
  </code></pre>
  
  <p>It says the 'CachedNetworkImageProvider.load' has fewer positional arguments than those of overridden method 'ImageProvider.load'.</p>
  
  <p>and when I hit the flutter run, it is giving me the following </p>
  
  <pre><code>/C:/Users/Acer/AppData/Roaming/Pub/Cache/hosted/pub.dartlang.org/cached_network_image-1.1.3/lib/src/cached_network_image_provider.dart:42:24: Error: The method 'CachedNetworkImageProvider.load' has fewer positional arguments than those of overridden method 'ImageProvider.load'.  
    ImageStreamCompleter load(CachedNetworkImageProvider key) {
                         ^
  /D:/Flutter/flutter/packages/flutter/lib/src/painting/image_provider.dart:403:24: Context: This is the overridden method ('load').
    ImageStreamCompleter load(T key, DecoderCallback decode);
                         ^
  </code></pre>