Hibok/lib/chat/full_img_view.dart

import 'dart:io';
import 'dart:typed_data';

import 'package:chat/chat/download_item.dart';
import 'package:chat/generated/i18n.dart';
import 'package:chat/models/ChatMsg.dart';
import 'package:flutter/material.dart';
import 'package:image_gallery_saver/image_gallery_saver.dart';
import 'package:oktoast/oktoast.dart';

import '../r.dart';

class PhotoPage extends StatefulWidget {
  final MsgModel msg;
  PhotoPage({this.msg});
  @override
  _PhotoPageState createState() => _PhotoPageState();
}

class _PhotoPageState extends State<PhotoPage>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<Offset> _animation;
  Offset _offset = Offset.zero;
  double _scale = 1.0;
  Offset _normalizedOffset;
  double _previousScale;
  double _kMinFlingVelocity = 600.0;

  ImageProvider provider;

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

    getImgData();
    _controller = AnimationController(vsync: this);
    _controller.addListener(() {
      setState(() {
        _offset = _animation.value;
      });
    });
  }

  getImgData() {
    if (widget.msg.localFile != null) {
      var fileData = File(widget.msg.localFile).readAsBytesSync();
      provider = MemoryImage(fileData);
    } else {
      provider = MemoryImage(Uint8List.fromList(widget.msg.msgContent));
    }
  }

  @override
  void dispose() {
    _controller.stop();
    _controller.dispose();

    super.dispose();
  }

  Offset _clampOffset(Offset offset) {
    final Size size = context.size;
    // widget的屏幕宽度
    final Offset minOffset = Offset(size.width, size.height) * (1.0 - _scale);
    // 限制他的最小尺寸
    return Offset(
        offset.dx.clamp(minOffset.dx, 0.0), offset.dy.clamp(minOffset.dy, 0.0));
  }

  void _handleOnScaleStart(ScaleStartDetails details) {
    setState(() {
      _previousScale = _scale;
      _normalizedOffset = (details.focalPoint - _offset) / _scale;
      // 计算图片放大后的位置
      _controller.stop();
    });
  }

  void _handleOnScaleUpdate(ScaleUpdateDetails details) {
    setState(() {
      _scale = (_previousScale * details.scale).clamp(1.0, 3.0);
      // 限制放大倍数 1~3倍
      _offset = _clampOffset(details.focalPoint - _normalizedOffset * _scale);
      // 更新当前位置
    });
  }

  void _handleOnScaleEnd(ScaleEndDetails details) {
    final double magnitude = details.velocity.pixelsPerSecond.distance;
    if (magnitude < _kMinFlingVelocity) return;
    final Offset direction = details.velocity.pixelsPerSecond / magnitude;
    // 计算当前的方向
    final double distance = (Offset.zero & context.size).shortestSide;
    // 计算放大倍速，并相应的放大宽和高，比如原来是600*480的图片，放大后倍数为1.25倍时，宽和高是同时变化的
    _animation = _controller.drive(Tween<Offset>(
        begin: _offset, end: _clampOffset(_offset + direction * distance)));
    _controller
      ..value = 0.0
      ..fling(velocity: magnitude / 1000.0);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        Navigator.pop(context);
      },
      onScaleStart: _handleOnScaleStart,
      onScaleUpdate: _handleOnScaleUpdate,
      onScaleEnd: _handleOnScaleEnd,
      child: Material(
          child: DownloadItem(
        msg: widget.msg,
        isAutoDown: false,
        onComplete: () {
          getImgData();
          setState(() {});
        },
        child: Transform(
            transform: Matrix4.identity()
              ..translate(_offset.dx, _offset.dy)
              ..scale(_scale),
            child: Stack(
              children: <Widget>[
                Image(
                  fit: BoxFit.fitWidth,
                  image: provider ?? AssetImage(R.assetsImagesIcAlbum),
                ),
                
                Positioned(
                    right: 10,
                    bottom: 10,
                    child: InkWell(
                        onTap: saveToGallery,
                        child: Container(
                          padding: EdgeInsets.all(5),
                          decoration: BoxDecoration(
                              color: Colors.grey.withAlpha(150),
                              borderRadius: BorderRadius.circular(8)),
                          child: Icon(Icons.save_alt, color: Colors.white70),
                        )))
              ],
            )),
      )),
    );
  }

  saveToGallery() async {
    if (widget.msg.localFile != null) {
      var data= File(widget.msg.localFile).readAsBytesSync();
      ImageGallerySaver.saveImage(data).then((res) {
        print(res);
        if (res != null) {
          showToast(I18n.of(context).successfully_saved);
        }
      });
    } else {
      ImageGallerySaver.saveImage(Uint8List.fromList(widget.msg.msgContent))
          .then((res) {
        print(res);
        if (res != null) {
          showToast(I18n.of(context).successfully_saved);
        }
      });
    }
  }
}