Q:

Check image is loaded in Image.network widget in flutter

I am new to Flutter. I try to load network image using image.network widget. it's work fine but sometimes it's take time to load.I added tap listener to image.network during tap i need to check image is fully load or not based on the result I need to redirect page. how to check image is loaded or not ? 
Code:
new Image.network('http://via.placeholder.com/350x150')

Any help will be appreciated, thank you in advance

A:

You may use the loadingBuilder which is inbuilt feature from flutter for Image.Network
I did it as below:
Image.network(imageURL,fit: BoxFit.cover,
  loadingBuilder:(BuildContext context, Widget child,ImageChunkEvent loadingProgress) {
  if (loadingProgress == null) return child;
    return Center(
      child: CircularProgressIndicator(
      value: loadingProgress.expectedTotalBytes != null ? 
             loadingProgress.cumulativeBytesLoaded / loadingProgress.expectedTotalBytes
             : null,
      ),
    );
  },
),

A:

for this kind of issues it's good to use the cached_network_image
so you can provide a placeholder when the image is loading and an error widget in case a resource fails to load
String url = "http://via.placeholder.com/350x150";
CachedNetworkImage(
       imageUrl: url,
       placeholder: (context,url) => CircularProgressIndicator(),
       errorWidget: (context,url,error) => new Icon(Icons.error),
     ),

A:

for ones who do not need to cache the image can use meet_network_image package,
The package basic usage : 
                MeetNetworkImage(
                  imageUrl:
                      "https://random.dog/3f62f2c1-e0cb-4077-8cd9-1ca76bfe98d5.jpg",
                  loadingBuilder: (context) => Center(
                        child: CircularProgressIndicator(),
                      ),
                  errorBuilder: (context, e) => Center(
                        child: Text('Error appear!'),
                      ),
                )

In addition, you can do that by yourself with using a FutureBuilder,
We need to get data with http call that way, we need to import http before import you also need to add pubspec.yaml and run the command flutter packages get
import 'package:http/http.dart' as http;

  FutureBuilder(
    // Paste your image URL inside the htt.get method as a parameter
    future: http.get(
        "https://random.dog/3f62f2c1-e0cb-4077-8cd9-1ca76bfe98d5.jpg"),
    builder: (BuildContext context, AsyncSnapshot<http.Response> snapshot) {
      switch (snapshot.connectionState) {
        case ConnectionState.none:
          return Text('Press button to start.');
        case ConnectionState.active:
        case ConnectionState.waiting:
          return CircularProgressIndicator();
        case ConnectionState.done:
          if (snapshot.hasError)
            return Text('Error: ${snapshot.error}');
          // when we get the data from the http call, we give the bodyBytes to Image.memory for showing the image
          return Image.memory(snapshot.data.bodyBytes);
      }
      return null; // unreachable
    },
  );

