From e10b3dfe79896a2718a9fba321b781bacea62a85 Mon Sep 17 00:00:00 2001
From: sant009 <530705296@qq.com>
Date: Tue, 14 Aug 2018 20:52:48 +0800
Subject: [PATCH] Added HeroPhotoView class which is more suitable for using
 with Hero widget.

---
 API.md                   | 37 +++++++++++++++
 lib/hero_photo_view.dart | 97 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 lib/hero_photo_view.dart

diff --git a/API.md b/API.md
index a645a614..d97197e2 100644
--- a/API.md
+++ b/API.md
@@ -73,4 +73,41 @@ dynamic ([double](https://docs.flutter.io/flutter/dart-core/double-class.html) o
 bool gaplessPlayback
 })
 
+## HeroPhotoView class
 
+A specific [PhotoView](/lib/photo_view.dart) used in playing [Hero](https://docs.flutter.io/flutter/widgets/Hero-class.html) animation.
+
+#### Sample code
+
+```dart
+new HeroPhotoView(
+  imageProvider: imageProvider,
+  backgroundColor: Colors.white,
+  minScale: PhotoViewScaleBoundary.contained,
+  maxScale: 2.0,
+  gaplessPlayback: false,
+  size: MediaQuery.of(context).size
+);
+```
+
+### Constructor
+
+[HeroPhotoView](/lib/hero_photo_view.dart)({
+@required [ImageProvider](https://docs.flutter.io/flutter/painting/ImageProvider-class.html) imageProvider,
+[Color](https://docs.flutter.io/flutter/dart-ui/Color-class.html) backgroundColor,
+dynamic ([double](https://docs.flutter.io/flutter/dart-core/double-class.html) or [PhotoViewScaleBoundary](/lib/photo_view_scale_boundary.dart)) minScale,
+dynamic ([double](https://docs.flutter.io/flutter/dart-core/double-class.html) or [PhotoViewScaleBoundary](/lib/photo_view_scale_boundary.dart)) maxScale, 
+bool gaplessPlayback,
+[Size](https://docs.flutter.io/flutter/dart-ui/Size-class.html) size})
+
+Instead of using [FutureBuilder](https://docs.flutter.io/flutter/widgets/FutureBuilder-class.html) in the normal [PhotoView](/lib/photo_view.dart), [HeroPhotoView](/lib/hero_photo_view.dart) uses [setState()](https://docs.flutter.io/flutter/widgets/State/setState.html) method to update UI after [ImageProvider](https://docs.flutter.io/flutter/painting/ImageProvider-class.html) being resolved.
+
+The zoom scale can be clamped by `minScale` and `maxScale` params. 
+
+`backgroundColor`, changes the background behind image, defaults to `Colors.black`. 
+
+The parameter `gaplessPlayback` is used to continue showing the old image (`true`), or briefly show nothing (`false`), when the `imageProvider` changes. By default it's set to `false`.
+
+`size` defines the size of the scaling base of the image inside `PhotoView`, by default it is `MediaQuery.of(context).size`. This param is used by `PhotoViewInline` class.
+
+**All but `imageProvider` are optional**
diff --git a/lib/hero_photo_view.dart b/lib/hero_photo_view.dart
new file mode 100644
index 00000000..315a68f8
--- /dev/null
+++ b/lib/hero_photo_view.dart
@@ -0,0 +1,97 @@
+import 'dart:async';
+import 'package:flutter/material.dart';
+import 'package:photo_view/photo_view.dart';
+import 'package:photo_view/photo_view_image_wrapper.dart';
+import 'package:photo_view/photo_view_scale_boundaries.dart';
+import 'package:photo_view/photo_view_scale_state.dart';
+import 'package:photo_view/photo_view_utils.dart';
+
+export 'package:photo_view/photo_view_scale_boundary.dart';
+
+class HeroPhotoView extends PhotoView {
+  HeroPhotoView({
+    Key key,
+    @required ImageProvider imageProvider,
+    Color backgroundColor = const Color.fromRGBO(0, 0, 0, 1.0),
+    minScale,
+    maxScale,
+    bool gaplessPlayback = false,
+    Size size,
+  }) : super(
+            key: key,
+            imageProvider: imageProvider,
+            backgroundColor: backgroundColor,
+            minScale: minScale,
+            maxScale: maxScale,
+            gaplessPlayback: gaplessPlayback,
+            size: size);
+
+  @override
+  State<StatefulWidget> createState() {
+    return new _HeroPhotoViewState();
+  }
+}
+
+class _HeroPhotoViewState extends State<HeroPhotoView> {
+  PhotoViewScaleState _scaleState;
+  GlobalKey containerKey = new GlobalKey();
+  ImageInfo _imageInfo;
+
+  Future<ImageInfo> _getImage() {
+    Completer completer = new Completer<ImageInfo>();
+    ImageStream stream = widget.imageProvider.resolve(new ImageConfiguration());
+    var listener = (ImageInfo info, bool completed) {
+      completer.complete(info);
+      setState(() {
+        _imageInfo = info;
+      });
+    };
+    stream.addListener(listener);
+    completer.future.then((_) {
+      stream.removeListener(listener);
+    });
+    return completer.future;
+  }
+
+  void onDoubleTap() {
+    setState(() {
+      _scaleState = nextScaleState(_scaleState);
+    });
+  }
+
+  void onStartPanning() {
+    setState(() {
+      _scaleState = PhotoViewScaleState.zooming;
+    });
+  }
+
+  @override
+  void initState() {
+    _getImage();
+    super.initState();
+    _scaleState = PhotoViewScaleState.contained;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (_imageInfo == null) {
+      return new SizedBox();
+    }
+    return new PhotoViewImageWrapper(
+      onDoubleTap: onDoubleTap,
+      onStartPanning: onStartPanning,
+      imageProvider: widget.imageProvider,
+      imageInfo: _imageInfo,
+      scaleState: _scaleState,
+      backgroundColor: widget.backgroundColor,
+      gaplessPlayback: widget.gaplessPlayback,
+      size: widget.size ?? MediaQuery.of(context).size,
+      scaleBoundaries: new ScaleBoundaries(
+        widget.minScale ?? 0.0,
+        widget.maxScale ?? 100000000000.0,
+        imageInfo: _imageInfo,
+        size: widget.size ?? MediaQuery.of(context).size,
+      ),
+    );
+  }
+}