Flutter实现Android原生相机拍照

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方法1：使用Flutter的camera插件（完整实现）

1. 完整依赖与权限配置

# pubspec.yaml
dependencies:
  flutter:
    sdk: flutter
  camera: ^0.10.5+2
  path_provider: ^2.0.15 # 用于获取存储路径
  path: ^1.8.3           # 用于路径操作
  permission_handler: ^10.4.0 # 权限处理

2. AndroidManifest.xml 配置

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

<!-- 在<application>标签内添加 -->
<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.fileprovider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_paths" />
</provider>

3. 创建文件路径配置 (res/xml/file_paths.xml)

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <external-path name="my_images" path="Android/data/${applicationId}/files/Pictures" />
</paths>

4. Flutter端完整代码

import 'dart:async';
import 'dart:io';
import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';

class CameraScreen extends StatefulWidget {
  @override
  _CameraScreenState createState() => _CameraScreenState();
}

class _CameraScreenState extends State<CameraScreen> {
  late CameraController _controller;
  late Future<void> _initializeControllerFuture;
  bool _isCameraReady = false;
  String? _lastImagePath;

  @override
  void initState() {
    super.initState();
    _setupCamera();
  }

  Future<void> _setupCamera() async {
    // 检查并请求权限
    final cameraStatus = await Permission.camera.status;
    final storageStatus = await Permission.storage.status;
    
    if (!cameraStatus.isGranted || !storageStatus.isGranted) {
      final results = await [
        Permission.camera,
        Permission.storage,
      ].request();
      
      if (!results[Permission.camera]!.isGranted || 
          !results[Permission.storage]!.isGranted) {
        return;
      }
    }

    // 获取可用相机
    final cameras = await availableCameras();
    final firstCamera = cameras.firstWhere(
      (camera) => camera.lensDirection == CameraLensDirection.back,
      orElse: () => cameras.first,
    );

    // 初始化控制器
    _controller = CameraController(
      firstCamera,
      ResolutionPreset.high,
      enableAudio: false,
      imageFormatGroup: ImageFormatGroup.jpeg,
    );

    _initializeControllerFuture = _controller.initialize().then((_) {
      if (!mounted) return;
      setState(() => _isCameraReady = true);
    });
  }

  Future<String> _takePicture() async {
    if (!_isCameraReady) throw 'Camera not ready';

    final Directory appDir = await getApplicationDocumentsDirectory();
    final String fileName = '${DateTime.now().millisecondsSinceEpoch}.jpg';
    final String savePath = join(appDir.path, fileName);

    try {
      final XFile image = await _controller.takePicture();
      final File savedImage = await File(image.path).copy(savePath);
      return savedImage.path;
    } on CameraException catch (e) {
      throw 'Camera error: ${e.description}';
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder<void>(
        future: _initializeControllerFuture,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return Stack(
              children: [
                CameraPreview(_controller),
                Positioned(
                  bottom: 30,
                  left: 0,
                  right: 0,
                  child: FloatingActionButton(
                    onPressed: () async {
                      try {
                        final path = await _takePicture();
                        setState(() => _lastImagePath = path);
                        print('Image saved to: $path');
                      } catch (e) {
                        ScaffoldMessenger.of(context).showSnackBar(
                          SnackBar(content: Text('Error: $e')),
                        );
                      }
                    },
                    child: Icon(Icons.camera),
                  ),
                )
              ],
            );
          } else {
            return Center(child: CircularProgressIndicator());
          }
        },
      ),
    );
  }
}

---

方法2：通过平台通道调用原生相机（完整实现）

Flutter端完整代码

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

class NativeCameraScreen extends StatefulWidget {
  @override
  _NativeCameraScreenState createState() => _NativeCameraScreenState();
}

class _NativeCameraScreenState extends State<NativeCameraScreen> {
  static const platform = MethodChannel('com.example/camera_channel');
  String? _imagePath;

  Future<void> _takePhoto() async {
    try {
      final String? path = await platform.invokeMethod('takePhoto');
      if (path != null) {
        setState(() => _imagePath = path);
        print('Photo path: $path');
      }
    } on PlatformException catch (e) {
      print("Failed to take photo: '${e.message}'.");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            if (_imagePath != null)
              Image.file(File(_imagePath!), height: 300),
            ElevatedButton(
              onPressed: _takePhoto,
              child: Text('Take Photo'),
            ),
          ],
        ),
      ),
    );
  }
}

Android端完整实现 (Kotlin)

// MainActivity.kt
package com.example.your_app_name

import android.Manifest
import android.app.Activity
import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.os.Bundle
import android.provider.MediaStore
import androidx.annotation.NonNull
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.core.content.FileProvider
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel
import java.io.File
import java.io.IOException
import java.text.SimpleDateFormat
import java.util.*

class MainActivity : FlutterActivity() {
    private val CHANNEL = "com.example/camera_channel"
    private var pendingResult: MethodChannel.Result? = null
    private var currentPhotoPath: String? = null
    private val REQUEST_IMAGE_CAPTURE = 1
    private val REQUEST_CAMERA_PERMISSION = 2

    override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
            when (call.method) {
                "takePhoto" -> {
                    pendingResult = result
                    checkCameraPermission()
                }
                else -> result.notImplemented()
            }
        }
    }

    private fun checkCameraPermission() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(
                this,
                arrayOf(Manifest.permission.CAMERA),
                REQUEST_CAMERA_PERMISSION
            )
        } else {
            dispatchTakePictureIntent()
        }
    }

    private fun dispatchTakePictureIntent() {
        Intent(MediaStore.ACTION_IMAGE_CAPTURE).also { takePictureIntent ->
            takePictureIntent.resolveActivity(packageManager)?.also {
                val photoFile: File? = try {
                    createImageFile()
                } catch (ex: IOException) {
                    pendingResult?.error("FILE_ERROR", ex.message, null)
                    null
                }
                photoFile?.also {
                    val photoURI: Uri = FileProvider.getUriForFile(
                        this,
                        "${BuildConfig.APPLICATION_ID}.fileprovider",
                        it
                    )
                    takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI)
                    startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE)
                }
            }
        }
    }

    @Throws(IOException::class)
    private fun createImageFile(): File {
        val timeStamp: String = SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(Date())
        val storageDir: File? = getExternalFilesDir("Pictures")
        return File.createTempFile(
            "JPEG_${timeStamp}_",
            ".jpg",
            storageDir
        ).apply {
            currentPhotoPath = absolutePath
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                dispatchTakePictureIntent()
            } else {
                pendingResult?.error("PERMISSION_DENIED", "Camera permission denied", null)
            }
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == REQUEST_IMAGE_CAPTURE) {
            when (resultCode) {
                Activity.RESULT_OK -> {
                    pendingResult?.success(currentPhotoPath)
                }
                Activity.RESULT_CANCELED -> {
                    pendingResult?.error("CANCELLED", "User cancelled photo", null)
                }
                else -> {
                    pendingResult?.error("CAPTURE_FAILED", "Image capture failed", null)
                }
            }
            pendingResult = null
        }
    }
}

---

关键问题解决方案

1. 文件存储问题（Android 10+适配）

// 在AndroidManifest.xml中添加
<application
    ...
    android:requestLegacyExternalStorage="true" // 临时解决方案
    >

或使用MediaStore API（推荐）：

private fun saveImageToGallery(context: Context, file: File) {
    val contentValues = ContentValues().apply {
        put(MediaStore.Images.Media.DISPLAY_NAME, file.name)
        put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg")
        put(MediaStore.Images.Media.RELATIVE_PATH, Environment.DIRECTORY_PICTURES)
    }

    val resolver = context.contentResolver
    val uri = resolver.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues)
    
    uri?.let {
        resolver.openOutputStream(it).use { output ->
            FileInputStream(file).use { input ->
                input.copyTo(output!!)
            }
        }
    }
}

2. 相机方向问题

在Flutter端处理相机方向：

@override
void didChangeAppLifecycleState(AppLifecycleState state) {
  if (state == AppLifecycleState.resumed) {
    _controller?.initialize().then((_) {
      if (!mounted) return;
      setState(() {});
    });
  }
}

// 监听设备方向
_controller.setOrientation(orientation);

3. 内存泄漏预防

@override
void dispose() {
  _controller?.dispose();
  super.dispose();
}

4. 异常处理最佳实践

try {
  // 相机操作
} on CameraException catch (e) {
  if (e.code == 'CameraAccessDenied') {
    // 处理权限问题
  } else {
    // 其他相机错误
  }
} on PlatformException catch (e) {
  // 平台通道错误
} catch (e) {
  // 通用错误
}

---

两种方法对比

特性	camera插件	平台通道
开发难度	★☆☆ (简单)	★★★ (复杂)
跨平台支持	是	需要单独实现iOS
功能控制	中等	完全控制
性能	较好	最优
依赖大小	较大	较小
定制能力	有限	无限
维护成本	低 (官方维护)	高 (需自行维护)

---

推荐方案选择

1. 大多数情况 ：使用camera插件

   • 官方维护
   • 跨平台支持
   • 减少平台特定代码

2. 需要高级功能时：使用平台通道

   • 需要特殊相机功能（HDR、手动对焦等）
   • 需要深度集成设备硬件
   • 需要完全控制图像处理流程

3. 混合方案：

   // 使用camera插件获取图像流
   final CameraImage image = await _controller.startImageStream((image) {
     // 处理实时图像数据
   });
   
   // 通过平台通道调用原生高级功能
   final hdrEnabled = await platform.invokeMethod('enableHDR');