Flutter從相冊選擇圖片和相機拍照（image_picker）

Flutter獲取相冊中的圖片和用相機拍照

在原生開發中，拍照及從圖庫選擇圖片是非常常見的需求，而且原生的圖片選擇第三方庫也有很多並且很完善了。
Flutter也給我們提供了好用的圖片選擇插件，ios和Android都能用的呦！
image_picker

先上圖

Flutter拍照：

Flutter選擇圖片

使用方法

首先添加依賴

在pubspec.yaml加入image_picker的依賴，版本號在github上找最新的即可。

如下：

依賴添加完成點擊右上角的 Packages get 出現finished及可。

使用
依賴添加完成之後我們就可以正常使用了
首先要導包：

import 'package:image_picker/image_picker.dart';

我們先來看看ImagePicker提供的方法，目前有兩個，選圖片和選視頻。
其中選擇圖片可以通過圖庫和相機的方式獲得。

我們主要來看看圖片

拍照

 var image = await ImagePicker.pickImage(source: ImageSource.camera);

相冊

 var image = await ImagePicker.pickImage(source: ImageSource.gallery);

是不是超級簡單，在Android上權限申請都不需要管。

下面是完整代碼：

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

class ImagePickerWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _ImagePickerState();
  }
}

class _ImagePickerState extends State<ImagePickerWidget> {
  var _imgPath;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("ImagePicker"),
        ),
        body: SingleChildScrollView(
          child: Column(
            children: <Widget>[
              _ImageView(_imgPath),
              RaisedButton(
                onPressed: _takePhoto,
                child: Text("拍照"),
              ),
              RaisedButton(
                onPressed: _openGallery,
                child: Text("選擇照片"),
              ),
            ],
          ),
        ));
  }

  /*圖片控件*/
  Widget _ImageView(imgPath) {
    if (imgPath == null) {
      return Center(
        child: Text("請選擇圖片或拍照"),
      );
    } else {
      return Image.file(
        imgPath,
      );
    }
  }

  
  /*拍照*/
  _takePhoto() async {
    var image = await ImagePicker.pickImage(source: ImageSource.camera);

    setState(() {
      _imgPath = image;
    });
  }

  /*相冊*/
  _openGallery() async {
    var image = await ImagePicker.pickImage(source: ImageSource.gallery);
    setState(() {
      _imgPath = image;
    });
  }
}

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注意事項

當圖片過長超過顯示寬高度的話，可能會報 The overflowing RenderFlex has an orientation of Axis.vertical. 這個錯，且底部會有黃色的警告。
具體報錯信息大概如下：

══╡ 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.

這裏我們直接使用 SingleChildScrollView（單個子控件的滾動佈局控件） 即可。

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需要demo的可以下載： Flutter拍照和相冊選擇圖片Demo

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