flutter拍照功能

先说用到的3个文件

• pubspec.yaml 安装必要包
• AndroidManifest.xml 添加权限（android/src/main）
• api.dart 封装一些系统的方法 （lib/utils）
• main.dart 初始化时，获取可用照相机，省去拍照页面的等待黑屏时间
• camera 拍照demo

pubspec.yaml

  camera: ^0.5.6+3
  path_provider: ^1.4.4

AndroidManifest.xml

     <!-- 获取相机权限 -->
    <uses-permission android:name="android.permission.CAMERA" />
    <!-- 储存权限 -->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

api.dart

import 'package:camera/camera.dart';
List<CameraDescription> cameras;
CameraController controller;

// 获取照相机
Future<void> getCamera() async {
  cameras = await availableCameras();
}

mian.dart

import './utils/api.dart';
import './mainPage.dart';
Future<void> main() async {
  getCamera();
  runApp(MyApp());
}
// 省略 .....

camera.dart 重点来了

• imagePath 用来保存拍照的地址
• initState时获取后摄像头，如果用前摄像头（cameras[1]）

class CameraPageState extends State<Camera> {
  String imagePath ; 
  @override
  void initState(){
    super.initState();
    // 调用相机
    controller = CameraController(cameras[0], ResolutionPreset.medium);
    controller.initialize().then((_) {
      if (!mounted) {
        return;
      }
      setState(() {});
    });
  }

页面布局，上方显示 拍照预览，下方为按钮

  Widget build(BuildContext context) {
    return Scaffold(
      body:new Container(
        child:Stack(children: <Widget>[
          new Column(
            children: <Widget>[
              Expanded(
                flex: 3,
                child: _cameraPreviewWidget(),
              ),
              Expanded(
                flex: 1,
                child: _takePictureLayout()
              )
            ],
          ),
          getPhotoPreview()
        ],)
      )
    );
  }

相机预览显示

  Widget _cameraPreviewWidget() {
    print(controller);
    if (controller == null || !controller.value.isInitialized) {
      return new Scaffold(
        appBar: AppBar(
          title: const Text('camera'),
        ),
       body: GestureDetector(
          onTap:(){
            print('已被点击');
            onTakePictureButtonPressed();
          },
          child: Text('点我拍照')
        )
      );
    }
    return new Container(
      child:AspectRatio(
        aspectRatio:controller.value.aspectRatio,
        child: CameraPreview(controller),
      )
    );
  }

拍照按钮布局

  Widget _takePictureLayout() {
    return new Align(
      alignment: Alignment.bottomCenter,
      child: new Container(
        color: Colors.black,
        alignment: Alignment.center,
        child:  new IconButton(
          iconSize: 50.0,
          onPressed: controller != null &&
              controller.value.isInitialized &&
              !controller.value.isRecordingVideo
              ? onTakePictureButtonPressed
              : null,
          icon: Icon(
            Icons.photo_camera,
            color: Colors.white,
          ),
        ),
    ));
  }

拍完预览

  Widget getPhotoPreview() {
    if( null != imagePath){
      return new Container(
        width:double.infinity,
        height: double.infinity,
        color: Colors.black,
        alignment: Alignment.center,
        child: Image.file(File(imagePath)),
      );
    }else{
      return new Container(
        height: 1.0,
        width: 1.0,
        color: Colors.black,
        alignment: Alignment.bottomLeft,
      );
    }
  }

保存图片操作

String timestamp() => DateTime.now().millisecondsSinceEpoch.toString();
Future<String> takePicture() async {
    if (!controller.value.isInitialized) {
      // showInSnackBar('Error: select a camera first.');
      return null;
    }
    // getApplicationDocumentsDirectory  文档目录
    final Directory extDir = await getExternalStorageDirectory();
    final String dirPath = '${extDir.path}/Pictures/flutter_test';
    print(dirPath);
    await Directory(dirPath).create(recursive: true);
    final String filePath = '$dirPath/${timestamp()}.jpg';
    print(filePath);
    if (controller.value.isTakingPicture) {
      // A capture is already pending, do nothing.
      return null;
    }

    try {
      await controller.takePicture(filePath);
      print('保存成功');
    } on CameraException catch (e) {
      print('保存失败');
      print(e);
      return null;
    }
    return filePath;
  }