Check image is loaded in Image.network widget in flutter

Question

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 ima

Answer 1

thank you for your comment thats help to resolve the situation that how to know if the image is loaded or not hope that help

I use a StatefulWidget need a editing depend on your AffichScreen

situation :

 -i have an url that i enter 
 -if url is correct affich the image if not affich an icon
 -if empty affich a Text()
 -precacheImage check if the url is correct if not give an error and change _loadingimage(bool) to false to affich the icon eror
 -i use a NetworkImage to check with precacheImage and before affich use a Image.network 



   bool _loadingimage;
ImageProvider _image;
Image _imagescreen;

@override
  void initState() {
    _loadingimage = true;
    _imageUrlfocusNode.addListener(_updateImageUrl);
    super.initState();
  }

   @override
  void dispose() {
    _imageUrlfocusNode.removeListener(_updateImageUrl);
    _quantityfocusNode.dispose();
    _imageUrlConroller.dispose();
    _imageUrlfocusNode.dispose();
    super.dispose();
  }

  void _updateImageUrl() {
    setState(() {
      _image = NetworkImage(_imageUrlConroller.text);
    });
    if (!_imageUrlfocusNode.hasFocus) {
      if (_imageUrlConroller.text.isNotEmpty) {
        setState(() {
          loadimage();
        });
      }
    }
  }

  void loadimage() {
    _loadingimage = true;
    precacheImage(_image, context, onError: (e, stackTrace) {
      // log.fine('Image ${widget.url} failed to load with error $e.');
      print('error $e');
      setState(() {
        _loadingimage = false;
        print(_loadingimage);
      });
    });
    if (_loadingimage == true) {
      _imagescreen = Image.network(
        _imageUrlConroller.text,
        fit: BoxFit.fill,
      );
    }
  }



  Container(
                              width: 100,
                              height: 100,
                              margin: EdgeInsets.only(top: 13, right: 11),
                              decoration: BoxDecoration(
                                border: Border.all(
                                  width: 1,
                                  color: Colors.grey,
                                ),
                              ),
                              child:_imageUrlConroller.text.isEmpty
                                      ? Text('enter an url')
                                      : !_loadingimage
                                          ? Container(
                                              child: Icon(Icons.add_a_photo),
                                            )
                                          : Container(
                                              child: _imagescreen,
                                            ),
                            ),

Answer 2

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,
      ),
    );
  },
),

Answer 3

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),
     ),

Answer 4

You could use a FadeInImage with a placeholder to do it

When displaying images using the default Image widget, you might notice they simply pop onto the screen as they’re loaded. This might feel visually jarring to your users.

Instead, wouldn’t it be nice to display a placeholder at first, and images would fade in as they’re loaded? Use the FadeInImage widget for exactly this purpose.

FadeInImage works with images of any type: in-memory, local assets, or images from the internet.

You can also consider using local assets for placeholders. First, add the asset to the project’s pubspec.yaml file (for more details, see Adding assets and images):

Complete example

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final title = 'Fade in images';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(title),
        ),
        body: Center(
          child: FadeInImage.assetNetwork(
            placeholder: 'assets/loading.gif',
            image: 'https://picsum.photos/250?image=9',
          ),
        ),
      ),
    );
  }
}

Answer 5

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
    },
  );