mutli_image_picker/example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:photo/photo.dart';
import 'package:photo_manager/photo_manager.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Pick Image Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Pick Image Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String currentSelected = "";

  void _pickImage() async {
    List<ImageEntity> imgList = await PhotoPicker.pickImage(
      context: context,
      themeColor: Colors.green,
      padding: 5.0,
      dividerColor: Colors.deepOrange,
      disableColor: Colors.grey.shade300,
      itemRadio: 0.88,
      maxSelected: 8,
      provider: CNProvider(),
      rowCount: 5,
      textColor: Colors.white,
      thumbSize: 250,
    );

    List<String> r = [];

    for(var e in imgList){
      var file = await e.file;
      r.add(file.absolute.path);
    }

    currentSelected = r.join("\n\n");

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: Container(
        child: Center(
          child: Text('$currentSelected'),
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _pickImage,
        tooltip: 'pickImage',
        child: new Icon(Icons.add),
      ),
    );
  }
}