flutter 相册和摄像头（软硬交互调自身系统）image_picker

首先必须注意一点：在升级flutter1.9+之后,flutter默认的iOS项目为swift,Android的默认项目为kotlin,而且通过IDEA创建的flutter项目,即使勾选了语言为oc,但是创建后的项目仍然是swift,颇为头疼.这里我们讲解的是基于iOS的OC和Android的JAVA来做的，毕竟我还是水手还没上岸成为干货（功力不足）。总之先跑通，再深究。

image_picker使用方法

首先添加依赖

在pubspec.yaml加入image_picker的依赖，版本号在github上找最新的即可。

如下：最新的是可以在这里找到：https://pub.dev/flutter/packages?q=image_picker，输入：image_picker即可搜索到最新版本，这里用老版本（稳）

 依赖添加完成点击右上角的 Packages get 出现finished及可。

使用
依赖添加完成之后我们就可以正常使用了

是不是超级简单，我们权限申请都不需要管。

下面是完整代码：

import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart'; //在pubspec.yaml加入image_picker的依赖,image_picker: ^0.5.0+3

void main() {
  runApp( MaterialApp(
    title: 'Flutter gesture',
//    home: TutorialHome(),
    home: AuthenticationId(),
  ));
}


class AuthenticationId extends StatefulWidget {
  @override
  _AuthenticationIdState createState() => _AuthenticationIdState();
}
class _AuthenticationIdState extends State<AuthenticationId>{
  var imgPath;
  /*拍照*/
  takePhoto() async {
    var image = await ImagePicker.pickImage(source: ImageSource.camera);

    setState(() {
      imgPath = image;
    });
  }
  /*相册*/
  openGallery() async {
    var image = await ImagePicker.pickImage(source: ImageSource.gallery);
    setState(() {
      imgPath = image;
    });
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("认证"),
          elevation: 0.0,
        ),
        body: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                child: imgPath == null ? Text('请选择拍照'):Image.file(imgPath),
              ),
              RaisedButton(
                onPressed: takePhoto,
                child: Text("拍照"),
              ),
              RaisedButton(
                onPressed: openGallery,
                child: Text("选择照片"),
              ),
            ],
          ),
        ));
  }
}

注意事项
当图片过长超过显示宽高度的话，可能会报 The overflowing RenderFlex has an orientation of Axis.vertical. 这个错，且底部会有黄色的警告。
具体报错信息大概如下：

══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (10595): The following message was thrown during layout:
I/flutter (10595): A RenderFlex overflowed by 177 pixels on the bottom.
I/flutter (10595):
I/flutter (10595): The overflowing RenderFlex has an orientation of Axis.vertical.
I/flutter (10595): The edge of the RenderFlex that is overflowing has been marked in the rendering with a yellow and
I/flutter (10595): black striped pattern. This is usually caused by the contents being too big for the RenderFlex.
I/flutter (10595): Consider applying a flex factor (e.g. using an Expanded widget) to force the children of the
I/flutter (10595): RenderFlex to fit within the available space instead of being sized to their natural size.
I/flutter (10595): This is considered an error condition because it indicates that there is content that cannot be
I/flutter (10595): seen. If the content is legitimately bigger than the available space, consider clipping it with a
I/flutter (10595): ClipRect widget before putting it in the flex, or using a scrollable container rather than a Flex,
I/flutter (10595): like a ListView.

这里我们直接使用 SingleChildScrollView（单个子控件的滚动布局控件） 即可。

原文不足的地方我这里（上面）已经补全了。
原文出处：https://blog.csdn.net/yuzhiqiang_1993/article/details/88345232（）