如何在Flutter中使用设备闪光灯？求Dart 3兼容方案

兼容Dart 3的第三方包 #

• camera：官方维护的包，完全适配Dart 3。它不仅支持闪光灯控制，还提供完整的相机功能。可以通过CameraController的torchMode属性切换闪光灯状态，配合Timer就能实现定时开关。
• torch_light：最新版本已适配Dart 3，API极简，专门用于闪光灯控制，无需处理额外的相机逻辑，只需要申请相机权限即可使用。

无依赖原生实现方式 #

如果不想用第三方包，可以通过Flutter的MethodChannel直接调用原生系统API，以下是Android和iOS的具体实现：

Android 端步骤 #

1. 在AndroidManifest.xml中添加权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera.flash" android:required="false" />

2. 编写Kotlin原生代码处理闪光灯控制：

class MainActivity : FlutterActivity() {
    private var cameraManager: CameraManager? = null
    private var cameraId: String? = null

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
        cameraId = cameraManager?.cameraIdList?.firstOrNull()

        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, "flash_channel").setMethodCallHandler { call, result ->
            when (call.method) {
                "turnOnFlash" -> {
                    try {
                        cameraId?.let {
                            cameraManager?.setTorchMode(it, true)
                        }
                        result.success(true)
                    } catch (e: Exception) {
                        result.error("FLASH_ERROR", e.message, null)
                    }
                }
                "turnOffFlash" -> {
                    try {
                        cameraId?.let {
                            cameraManager?.setTorchMode(it, false)
                        }
                        result.success(true)
                    } catch (e: Exception) {
                        result.error("FLASH_ERROR", e.message, null)
                    }
                }
                else -> result.notImplemented()
            }
        }
    }
}

iOS 端步骤 #

1. 在Info.plist中添加权限描述：

<key>NSCameraUsageDescription</key>
<string>需要相机权限来控制闪光灯</string>

2. 编写Swift原生代码处理闪光灯控制：

import UIKit
import Flutter
import AVFoundation

class MainFlutterViewController: FlutterViewController {
    private var captureDevice: AVCaptureDevice?

    override func viewDidLoad() {
        super.viewDidLoad()
        captureDevice = AVCaptureDevice.default(for: .video)

        let channel = FlutterMethodChannel(name: "flash_channel", binaryMessenger: self.binaryMessenger)
        channel.setMethodCallHandler { [weak self] call, result in
            guard let self = self else { return }
            switch call.method {
            case "turnOnFlash":
                do {
                    guard let device = self.captureDevice else {
                        result.error("FLASH_ERROR", "未找到相机设备", nil)
                        return
                    }
                    try device.lockForConfiguration()
                    device.torchMode = .on
                    device.unlockForConfiguration()
                    result.success(true)
                } catch {
                    result.error("FLASH_ERROR", error.localizedDescription, nil)
                }
            case "turnOffFlash":
                do {
                    guard let device = self.captureDevice else {
                        result.error("FLASH_ERROR", "未找到相机设备", nil)
                        return
                    }
                    try device.lockForConfiguration()
                    device.torchMode = .off
                    device.unlockForConfiguration()
                    result.success(true)
                } catch {
                    result.error("FLASH_ERROR", error.localizedDescription, nil)
                }
            default:
                result.notImplemented()
            }
        }
    }
}

Flutter 端调用与定时逻辑 #

在Dart代码中，通过MethodChannel调用原生方法，并使用Timer.periodic实现定时开关：

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

class FlashTimer {
  static const _channel = MethodChannel('flash_channel');
  Timer? _toggleTimer;
  bool _isFlashActive = false;

  // 启动定时切换，interval为间隔秒数
  void startToggling(double interval) {
    _toggleTimer?.cancel();
    _toggleTimer = Timer.periodic(Duration(seconds: interval.toInt()), (_) async {
      _isFlashActive = !_isFlashActive;
      try {
        if (_isFlashActive) {
          await _channel.invokeMethod('turnOnFlash');
        } else {
          await _channel.invokeMethod('turnOffFlash');
        }
      } catch (e) {
        print("闪光灯控制失败: $e");
      }
    });
  }

  // 停止定时并关闭闪光灯
  void stopToggling() {
    _toggleTimer?.cancel();
    _channel.invokeMethod('turnOffFlash');
    _isFlashActive = false;
  }
}

内容的提问来源于stack exchange，提问作者Anjos