Flutter/画像/画像viewer

インストール

pubspec.yaml

dependencies:
  photo_view: ^0.9.1

公式

https://pub.dev/packages/photo_view

サンプル

ローカル画像

import 'package:photo_view/photo_view.dart';
PhotoView photoView = PhotoView(
      imageProvider: AssetImage("assets/image1.jpg"),
      minScale: PhotoViewComputedScale.contained * 1.0,
      maxScale: 2.0,
    );

ネット画像

import 'package:photo_view/photo_view.dart';
if (imageUrl != null) {
    PhotoView photoView = PhotoView(
          imageProvider: NetworkImage(imageUrl),
          // imageProvider: NetworkImage("http://wiki.nonip.net/skins/Vector/images/share/d.png"),
       );
}

imageUrlにはnullを一度でも入れると表示されなくなる。asyncを使ってる場合は注意。値渡しはprefを経由するなどではなく、Navigatorからそのまま値を渡したほうが良いかも。

次前へ移動できるviewer

    PhotoViewGallery photoViewGallery = PhotoViewGallery.builder(
          scrollPhysics: const BouncingScrollPhysics(),
          builder: (BuildContext context, int index) {
            NetworkImage networkImage = NetworkImage(imgs[index].url);
            FadeInImage image = FadeInImage.assetNetwork(
              placeholder: 'assets/loading.gif',
              image: imgs[index].url,
              fit: BoxFit.cover,
            );
            return PhotoViewGalleryPageOptions(
              imageProvider: networkImage,
              initialScale: PhotoViewComputedScale.contained,
              minScale: PhotoViewComputedScale.contained * 0.7,
              maxScale: PhotoViewComputedScale.covered * 2,
            );
          },
          itemCount: imgs.length,
          backgroundDecoration: BoxDecoration(
            color: Theme.of(context).canvasColor,
          ),
          loadingChild: Center(
            child: CircularProgressIndicator(),
          ),
        );

参考：https://resocoder.com/2019/05/04/flutter-photo-view-gallery-resize-rotate-image-carousel/

参考：https://www.cnblogs.com/gggggggxin/p/11195401.html

一覧から次前へ移動できるviewerへ

class ImageViewerPage extends StatefulWidget {
  final String title;
  final int initialIndex;
  PageController pageController;
  List<Img> imgs = [];
  ImageViewerPage({Key key, this.title, this.imgs, this.initialIndex}) : super(key: key) {
    pageController = PageController(initialPage: initialIndex);
  }
  @override
  _ImageViewerPageState createState() => _ImageViewerPageState();
}

class _ImageViewerPageState extends State<ImageViewerPage> {
  int currentIndex;
  bool initFlag = true;
  @override
  void initState() {
    super.initState();
    setState(() {
      currentIndex = widget.initialIndex;
    });
  }
  void onPageChanged(int index) {
      setState(() {
          currentIndex = index;
      });
  }
  @override
  Widget build(BuildContext context) {
    PhotoViewGallery photoViewGallery = PhotoViewGallery.builder(
      scrollPhysics: const BouncingScrollPhysics(),
      builder: (BuildContext context, int index) {
        NetworkImage networkImage = NetworkImage(widget.imgs[index].url);
        return PhotoViewGalleryPageOptions(
          imageProvider: networkImage,
          initialScale: PhotoViewComputedScale.contained,
          minScale: PhotoViewComputedScale.contained * 0.7,
          maxScale: PhotoViewComputedScale.covered * 2,
          heroAttributes: PhotoViewHeroAttributes(tag: widget.imgs[index].url),
        );
      },
      itemCount: widget.imgs.length,
      onPageChanged: onPageChanged,
      pageController: widget.pageController,
      backgroundDecoration: BoxDecoration(
        color: Theme.of(context).canvasColor,
      ),
      loadingChild: Center(
        child: CircularProgressIndicator(),
      ),
    );
    return Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.blue.withOpacity(0.3),
          elevation: 0.0,
          title: Text("画像",
              style: TextStyle(
                  fontSize: 16,
                  locale: Locale("ja", "JP")
              )
          ),
        ),
        extendBodyBehindAppBar: true,
        body: photoViewGallery
    );
  }
}

imgsにはnullを一度でも入れると初回の一枚目が開いてしまう。asyncを使って取得するのではなく、Navigatorからそのまま値を渡したほうが良い。

画像アニメーション(hero)

heroを使うには、遷移先、遷移元のimageを以下のようにする。tagの文字列を一致させる。

photoViewでは

PhotoViewGalleryPageOptions(
          heroAttributes: PhotoViewHeroAttributes(tag: url),
)

遷移先、遷移元

Hero(
    tag: url,
    child: Image.network(url)
),