##### demo 地址: https://github.com/iotjin/jh_flutter_demo

flutter好用的轮子推荐四-可定制的图片预览查看器photo_view
flutter九宫格图片查看器

效果图

关于九宫格布局实现

JhPhotoAllScreenShow 代码

import 'package:flutter/material.dart';
import 'package:photo_view/photo_view.dart';
import 'package:photo_view/photo_view_gallery.dart';

const Color selColor =Colors.white;
const Color otherColor = Colors.grey;

class FadeRoute extends PageRouteBuilder {
  final Widget page;
  FadeRoute({this.page}): super(
    pageBuilder: (
        BuildContext context,
        Animation<double> animation,
        Animation<double> secondaryAnimation,
        ) =>page,transitionsBuilder: (
      BuildContext context,
      Animation<double> animation,
      Animation<double> secondaryAnimation,
      Widget child,
      ) =>FadeTransition(
    opacity: animation,
    child: child,
  ),
  );
}




class JhPhotoAllScreenShow extends StatefulWidget {

      List imgDataArr=[];
      int index=0;
      String heroTag;
      PageController controller;
      GestureTapCallback onLongPress;

      JhPhotoAllScreenShow({
        Key key,
        @required this.imgDataArr,
        this.index,
        this.onLongPress,
        this.controller,
        this.heroTag
      }) : super(key: key){
        controller=PageController(initialPage: index);
      }

  @override
  _JhPhotoAllScreenShowState createState() => _JhPhotoAllScreenShowState();
}

class _JhPhotoAllScreenShowState extends State<JhPhotoAllScreenShow> {
  int currentIndex=0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    currentIndex=widget.index;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: <Widget>[
          Positioned(
              top: 0,
              left: 0,
              bottom: 0,
              right: 0,
              child:
              GestureDetector(
                child:
                Container(
                    color: Colors.black,
                    child: PhotoViewGallery.builder(
                      scrollPhysics: const BouncingScrollPhysics(),
                      builder: (BuildContext context, int index) {
                        return PhotoViewGalleryPageOptions(
                          imageProvider: NetworkImage(widget.imgDataArr[index]),
                          heroAttributes: widget.heroTag !=null?PhotoViewHeroAttributes(tag: widget.heroTag):null,

                        );
                      },
                      itemCount: widget.imgDataArr.length,
                      loadingChild: Container(),
                      backgroundDecoration: null,
                      pageController: widget.controller,
                      enableRotation: true,
                      onPageChanged: (index){
                        setState(() {
                          currentIndex=index;
                        });
                      },
                    )
                ),
                onTap: (){
                  Navigator.of(context).pop();
                },
                onLongPress: widget.onLongPress,

              )

          ),
          Positioned(
            top: MediaQuery.of(context).padding.top+30,
            width: MediaQuery.of(context).size.width,
            child: Center(
              child: Text("${currentIndex+1}/${widget.imgDataArr.length}",style: TextStyle(color: Colors.white,fontSize: 16)),
            ),
          ),
          Positioned(
            right: 10,
            top: MediaQuery.of(context).padding.top+15,
            child: IconButton(
              icon: Icon(Icons.close,size: 30,color: Colors.white,),
              onPressed: (){
                Navigator.of(context).pop();
              },
            ),
          ),
          
          Align(
              alignment: Alignment.bottomCenter,
              child:
              Container(
//                color: Colors.red,
                width: widget.imgDataArr.length>=6 ? 200:widget.imgDataArr.length<3 ? 50:100,
                height: widget.imgDataArr.length==1 ? 0:50,
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceAround,
                  children: List.generate(
                    widget.imgDataArr.length,
                        (i) => GestureDetector(
                      child: CircleAvatar(
//                      foregroundColor: Theme.of(context).primaryColor,
                        radius: 5.0,
                        backgroundColor: currentIndex == i ? selColor : otherColor,
                      ),
                    ),
                  ).toList(),
                ),
              )
          )
          
          
        ],
      ),
    );
  }
}

JhPhotoAllScreenShow2 代码

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

const Color selColor =Colors.white;
const Color otherColor = Colors.grey;

// 底部显示小圆点
class NinePictureAllScreenShow<T> extends PopupRoute<T> {
  final String barrierLabel;
  final List picList;
  final int index;
  int startX;
  int endX;

  NinePictureAllScreenShow(this.picList, this.index, {this.barrierLabel});

  @override
  Duration get transitionDuration => Duration(milliseconds: 2000);

  @override
  Color get barrierColor => Colors.black;  //背景颜色

  @override
  bool get barrierDismissible => true;

  AnimationController _animationController;

  @override
  AnimationController createAnimationController() {
    assert(_animationController == null);
    _animationController =
        BottomSheet.createAnimationController(navigator.overlay);
    return _animationController;
  }

  @override
  Widget buildPage(BuildContext context, Animation<double> animation,
      Animation<double> secondaryAnimation) {
    return MediaQuery.removePadding(
      removeTop: true,
      context: context,
      child: GestureDetector(
        child: AnimatedBuilder(
          animation: animation,
          builder: (BuildContext context, Widget child) => GestureDetector(
            onTap: () {
              Navigator.pop(context);
            },
            child: _PictureWidget(picList, index),
          ),
        ),
      ),
    );
  }
}

class _PictureWidget extends StatefulWidget {
  final List picList;
  final int index;

  _PictureWidget(this.picList, this.index);

  @override
  State createState() {
    return _PictureWidgetState();
  }
}

class _PictureWidgetState extends State<_PictureWidget> {
  int startX = 0;
  int endX = 0;
  int index = 0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    index = widget.index;
  }

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.transparent,
      child: new Container(
        width: double.infinity,
        padding: EdgeInsets.fromLTRB(0, 0, 0, 30),
        child: Stack(
          children: <Widget>[
            GestureDetector(
              child: Center(
                child: CachedNetworkImage(
                  imageUrl: widget.picList[index],
                  fit: BoxFit.fill,
                ),
              ),
              onHorizontalDragDown: (detail) {
                startX = detail.globalPosition.dx.toInt();
              },
              onHorizontalDragUpdate: (detail) {
                endX = detail.globalPosition.dx.toInt();
              },
              onHorizontalDragEnd: (detail) {
                _getIndex(endX - startX);
                setState(() {});
              },
              onHorizontalDragCancel: () {},
            ),

            Align(
                alignment: Alignment.bottomCenter,
                child:
                Container(
//                color: Colors.red,
                  width: widget.picList.length>=6 ? 200:widget.picList.length<3 ? 50:100,
                  height: 50,
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.spaceAround,
                    children: List.generate(
                      widget.picList.length,
                          (i) => GestureDetector(
                        child: CircleAvatar(
//                      foregroundColor: Theme.of(context).primaryColor,
                          foregroundColor: selColor,
                          radius: 5.0,
                          backgroundColor: index == i ? selColor : otherColor,
                        ),
                        onTap: () {
                          setState(() {
                            startX = endX = 0;
                            index = i;
                          });
                        },
                      ),
                    ).toList(),
                  ),
                )
            )

          ],
        ),
        alignment: Alignment.center,
      ),
    );
  }

  void _getIndex(int delta) {
    if (delta > 50) {
      setState(() {
        index--;
        index = index.clamp(0, widget.picList.length - 1);
      });
    } else if (delta < 50) {
      setState(() {
        index++;
        index = index.clamp(0, widget.picList.length - 1);
      });
    }
  }

}