flutter gif加載 獲取當前幀數 回圈次數

flutter gif圖片加載 可監聽總播發幀數 當前幀數 回圈次數 可自由拓展
代碼如下

import 'dart:io';
import 'dart:ui' as ui show Codec;
import 'dart:ui';
import 'package:flutter/foundation.dart';
import 'package:flutter/widgets.dart';

class GifCache {
  final Map<String, List<ImageInfo>> caches = Map();

  void clear() {
    caches.clear();
  }

  bool evict(Object key) {
    final List<ImageInfo>? pendingImage = caches.remove(key)!;
    if (pendingImage != null) {
      return true;
    }
    return false;
  }
}

class GifController extends AnimationController {
  GifController(
      {required TickerProvider vsync,
      double value = 0.0,
      Duration? reverseDuration = const Duration(milliseconds: 1000),
      Duration? duration = const Duration(milliseconds: 1000),
      AnimationBehavior? animationBehavior})
      : super.unbounded(
            value: value,
            reverseDuration: reverseDuration,
            duration: duration,
            animationBehavior: animationBehavior ?? AnimationBehavior.normal,
            vsync: vsync);

  int _frames = 0;

  bindValues(int len) {
    _frames = len;
  }

  int get frames {
    return _frames;
  }

  int get frame {
    return value.toInt();
  }

  int get playCount {
    return _playCount;
  }

  int _playCount = 0;

  @override
  void stop({bool canceled = true}) {
    super.stop(canceled: canceled);
  }

  void play() {
    repeat(min: 0, max: frames.toDouble(), period: duration);
  }
}

class GifImage extends StatefulWidget {
  GifImage({
    required this.image,
    required this.controller,
    this.semanticLabel,
    this.excludeFromSemantics = false,
    this.width,
    this.height,
    this.onFetchCompleted,
    this.color,
    this.colorBlendMode,
    this.fit,
    this.alignment = Alignment.center,
    this.repeat = ImageRepeat.noRepeat,
    this.centerSlice,
    this.matchTextDirection = false,
    this.initPlay = true,
  });

  final VoidCallback? onFetchCompleted;
  final GifController controller;
  final ImageProvider image;
  final double? width;
  final bool? initPlay;
  final double? height;
  final Color? color;
  final BlendMode? colorBlendMode;
  final BoxFit? fit;
  final AlignmentGeometry alignment;
  final ImageRepeat repeat;
  final Rect? centerSlice;
  final bool matchTextDirection;
  final String? semanticLabel;
  final bool excludeFromSemantics;

  @override
  State<StatefulWidget> createState() {
    return new GifImageState();
  }

  static GifCache cache = GifCache();
}

class GifImageState extends State<GifImage> {
  List<ImageInfo?>? _infos;
  ValueNotifier<int> _curIndex = ValueNotifier(-1);
  bool _fetchComplete = false;

  ImageInfo? get _imageInfo {
    if (!_fetchComplete) return null;
    return _infos == null ? null : _infos![_curIndex.value];
  }

  @override
  void initState() {
    super.initState();
    widget.controller.addListener(_listener);
    _curIndex.addListener(() {
      if (widget.controller.frame == widget.controller.frames - 1) {
        widget.controller._playCount++;
      }
    });
    fetchGif(widget.image).then((imageInfors) {
      if (mounted) {
        _infos = imageInfors;
        _fetchComplete = true;
        widget.controller.bindValues(_infos!.length);
        _curIndex.value = widget.controller.value.toInt();
        if (widget.onFetchCompleted != null) {
          widget.onFetchCompleted!();
        }
        if (widget.initPlay == true) {
          widget.controller.play();
        }
      }
    });
  }

  @override
  void dispose() {
    super.dispose();
    widget.controller.removeListener(_listener);
  }

  @override
  void didUpdateWidget(GifImage oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.controller != oldWidget.controller) {
      oldWidget.controller.removeListener(_listener);
      widget.controller.addListener(_listener);
    }
  }

  void _listener() {
    if (_curIndex.value != widget.controller.value && _fetchComplete) {
      _curIndex.value = widget.controller.value.toInt();
    }
  }

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

  @override
  Widget build(BuildContext context) {
     RawImage image =  RawImage(
      image: _imageInfo?.image,
      width: widget.width,
      height: widget.height,
      scale: _imageInfo?.scale ?? 1.0,
      color: widget.color,
      colorBlendMode: widget.colorBlendMode,
      fit: widget.fit,
      alignment: widget.alignment,
      repeat: widget.repeat,
      centerSlice: widget.centerSlice,
      matchTextDirection: widget.matchTextDirection,
    );
    if (widget.excludeFromSemantics) return image;
    return ValueListenableBuilder(
      valueListenable: _curIndex,
      builder: (context, index, child) {
        return Semantics(
          container: widget.semanticLabel != null,
          image: true,
          label: widget.semanticLabel == null ? '' : widget.semanticLabel,
          child:  RawImage(
            image: _imageInfo?.image,
            width: widget.width,
            height: widget.height,
            scale: _imageInfo?.scale ?? 1.0,
            color: widget.color,
            colorBlendMode: widget.colorBlendMode,
            fit: widget.fit,
            alignment: widget.alignment,
            repeat: widget.repeat,
            centerSlice: widget.centerSlice,
            matchTextDirection: widget.matchTextDirection,
          ),
        );
      },
    );
  }
}

final HttpClient _sharedHttpClient = HttpClient()..autoUncompress = false;

HttpClient get _httpClient {
  HttpClient client = _sharedHttpClient;
  assert(() {
    if (debugNetworkImageHttpClientProvider != null)
      client = debugNetworkImageHttpClientProvider!();
    return true;
  }());
  return client;
}

Future<List<ImageInfo>> fetchGif(ImageProvider provider) async {
  List<ImageInfo> infos = [];
  dynamic data;
  String key = provider is NetworkImage
      ? provider.url
      : provider is AssetImage
          ? provider.assetName
          : provider is MemoryImage
              ? provider.bytes.toString()
              : "";
  if (GifImage.cache.caches.containsKey(key)) {
    infos = GifImage.cache.caches[key]!;
    return infos;
  }
  if (provider is NetworkImage) {
    final Uri resolved = Uri.base.resolve(provider.url);
    final HttpClientRequest request = await _httpClient.getUrl(resolved);
    provider.headers?.forEach((String name, String value) {
      request.headers.add(name, value);
    });
    final HttpClientResponse response = await request.close();
    data = await consolidateHttpClientResponseBytes(
      response,
    );
  } else if (provider is AssetImage) {
    AssetBundleImageKey key = await provider.obtainKey(ImageConfiguration());
    data = await key.bundle.load(key.name);
  } else if (provider is FileImage) {
    data = await provider.file.readAsBytes();
  } else if (provider is MemoryImage) {
    data = provider.bytes;
  }

  ui.Codec codec = await PaintingBinding.instance!
      .instantiateImageCodec(data.buffer.asUint8List());
  infos = [];
  for (int i = 0; i < codec.frameCount; i++) {
    FrameInfo frameInfo = await codec.getNextFrame();
    //scale ??
    infos.add(ImageInfo(image: frameInfo.image));
  }
  GifImage.cache.caches.putIfAbsent(key, () => infos);
  return infos;
}

好了 去玩吧
呼叫示范

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'gif_image.dart';

void main() => runApp(StartPage());

class StartPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: TestPage(),
    );
  }
}

class TestPage extends StatefulWidget {
  @override
  _TestPageState createState() => _TestPageState();
}

class _TestPageState extends State<TestPage>
    with SingleTickerProviderStateMixin {
  late GifController controller = GifController(vsync: this);

  @override
  void initState() {
    super.initState();
    controller.addListener(() {
      setState(() {});
    });
  }

  Widget get initFloatingActionButton {
    return FloatingActionButton(
      backgroundColor: Colors.grey,
      elevation: 1,
      focusElevation: 1,
      onPressed: () {
        if (controller.isAnimating) {
          controller.stop();
        } else {
          controller.play();
        }
        setState(() {});
      },
      child: Icon(Icons.android),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: initFloatingActionButton,
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
      extendBody: true,
      body: Center(
          child: Container(
        width: 400,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              '總幀數：${controller.frames}\n'
              '當前幀數：${controller.frame}\n'
              '當前回圈次數：${controller.playCount}\n',
              maxLines: 4,
              overflow: TextOverflow.ellipsis,
            ),
            GifImage(
              controller: controller,
              image: AssetImage("image/964F914FA551BCD8D9F1C2F9C9DA2E67.gif"),
            )
          ],
        ),
      )),
    );
  }
}