添加错误回调的Image

gistfile1.txt

class ImageDemo extends StatefulWidget {
  @override
  _ImageDemoState createState() => _ImageDemoState();
}

class _ImageDemoState extends State<ImageDemo> {
  bool _err = false;

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          elevation: 0,
          title: Text(
            "ImageDemo",
            style: TextStyle(fontSize: 17, color: Colors.black87),
          ),
          bottom: PreferredSize(
            child: Divider(
              height: 1,
            ),
            preferredSize: Size(MediaQuery.of(context).size.width, 1),
          ),
        ),
        body: Center(
          child: Container(
            width: 100,
            height: 50,
            decoration: BoxDecoration(color: Colors.black45),
            child: _err
                ? Center(
                    child: Text("error widget"),
                  )
                : Image(
                    image: NetworkImageSSL(
                      "$_kImageUrl",
                      imageErrorListener: (ex, stack) {
                        setState(() {
                          _err = true;
                        });
                      },
                    ),
                  ),
          ),
        ));
  }
}

class NetworkImageSSL extends ImageProvider<NetworkImageSSL> {
  const NetworkImageSSL(this.url,
      {this.scale = 1.0, this.headers, this.imageErrorListener})
      : assert(url != null),
        assert(scale != null);

  final String url;

  final double scale;

  final Map<String, String> headers;

  final ImageErrorListener imageErrorListener;

  @override
  Future<NetworkImageSSL> obtainKey(ImageConfiguration configuration) {
    return new SynchronousFuture<NetworkImageSSL>(this);
  }

  @override
  ImageStreamCompleter load(NetworkImageSSL key) {
    var multiFrameImageStreamCompleter = new MultiFrameImageStreamCompleter(
        codec: _loadAsync(key),
        scale: key.scale,
        informationCollector: () {
          List<DiagnosticsNode> informationCollector;
          informationCollector.add(DiagnosticsProperty('Image provider', this));
          informationCollector.add(DiagnosticsProperty('Image key', key));
          return informationCollector;
        });
    
    ///添加Error Callback
    ImageStreamListener listener;
    listener = ImageStreamListener((imageInfo, ret) {
      multiFrameImageStreamCompleter.removeListener(listener);
    }, onError: (ex, stack) {
      multiFrameImageStreamCompleter.removeListener(listener);
      imageErrorListener?.call(ex, stack);
    });

    multiFrameImageStreamCompleter.addListener(listener);
    return multiFrameImageStreamCompleter;
  }

  static final HttpClient _httpClient = new HttpClient()
    ..badCertificateCallback = ((X509Certificate cert, String host, int port) {
      ///add https certificate check
      return true;
    });

  Future<ui.Codec> _loadAsync(NetworkImageSSL key) async {
    assert(key == this);

    final Uri resolved = Uri.base.resolve(key.url);
    final HttpClientRequest request = await _httpClient.getUrl(resolved);
    headers?.forEach((String name, String value) {
      request.headers.add(name, value);
    });
    final HttpClientResponse response = await request.close();
    if (response.statusCode != HttpStatus.ok) {
      throw new Exception(
          'HTTP request failed, statusCode: ${response?.statusCode}, $resolved');
    }

    final Uint8List bytes = await consolidateHttpClientResponseBytes(response);
    if (bytes.lengthInBytes == 0) {
      throw new Exception('NetworkImageSSL is an empty file: $resolved');
    }
    return await ui.instantiateImageCodec(bytes);
  }

  @override
  bool operator ==(dynamic other) {
    if (other.runtimeType != runtimeType) return false;
    final NetworkImageSSL typedOther = other;
    return url == typedOther.url && scale == typedOther.scale;
  }

  @override
  int get hashCode => hashValues(url, scale);

  @override
  String toString() => '$runtimeType("$url", scale: $scale)';
}