flutter/examples/api/lib/painting/image_provider/image_provider.0.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';
import 'dart:io';
import 'dart:ui' as ui;

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

@immutable
class CustomNetworkImage extends ImageProvider<Uri> {
  const CustomNetworkImage(this.url);

  final String url;

  @override
  Future<Uri> obtainKey(ImageConfiguration configuration) {
    final Uri result = Uri.parse(url).replace(
      queryParameters: <String, String>{
        'dpr': '${configuration.devicePixelRatio}',
        'locale': '${configuration.locale?.toLanguageTag()}',
        'platform': '${configuration.platform?.name}',
        'width': '${configuration.size?.width}',
        'height': '${configuration.size?.height}',
        'bidi': '${configuration.textDirection?.name}',
      },
    );
    return SynchronousFuture<Uri>(result);
  }

  static HttpClient get _httpClient {
    HttpClient? client;
    assert(() {
      if (debugNetworkImageHttpClientProvider != null) {
        client = debugNetworkImageHttpClientProvider!();
      }
      return true;
    }());
    return client ?? HttpClient()..autoUncompress = false;
  }

  @override
  ImageStreamCompleter loadImage(Uri key, ImageDecoderCallback decode) {
    final StreamController<ImageChunkEvent> chunkEvents = StreamController<ImageChunkEvent>();
    debugPrint('Fetching "$key"...');
    return MultiFrameImageStreamCompleter(
      codec: _httpClient.getUrl(key)
          .then<HttpClientResponse>((HttpClientRequest request) => request.close())
          .then<Uint8List>((HttpClientResponse response) {
            return consolidateHttpClientResponseBytes(
              response,
              onBytesReceived: (int cumulative, int? total) {
                chunkEvents.add(ImageChunkEvent(
                  cumulativeBytesLoaded: cumulative,
                  expectedTotalBytes: total,
                ));
              },
            );
          })
          .catchError((Object e, StackTrace stack) {
             scheduleMicrotask(() {
               PaintingBinding.instance.imageCache.evict(key);
             });
             return Future<Uint8List>.error(e, stack);
           })
          .whenComplete(chunkEvents.close)
          .then<ui.ImmutableBuffer>(ui.ImmutableBuffer.fromUint8List)
          .then<ui.Codec>(decode),
      chunkEvents: chunkEvents.stream,
      scale: 1.0,
      debugLabel: '"key"',
      informationCollector: () => <DiagnosticsNode>[
        DiagnosticsProperty<ImageProvider>('Image provider', this),
        DiagnosticsProperty<Uri>('URL', key),
      ],
    );
  }

  @override
  String toString() => '${objectRuntimeType(this, 'CustomNetworkImage')}("$url")';
}

void main() => runApp(const ExampleApp());

class ExampleApp extends StatelessWidget {
  const ExampleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: LayoutBuilder(
        builder: (BuildContext context, BoxConstraints constraints) {
          return Image(
            image: const CustomNetworkImage('https://flutter.github.io/assets-for-api-docs/assets/widgets/flamingos.jpg'),
            width: constraints.hasBoundedWidth ? constraints.maxWidth : null,
            height: constraints.hasBoundedHeight ? constraints.maxHeight : null,
          );
        },
      ),
    );
  }
}