Flutter Windows平台相机功能插件camera_windows的使用
Flutter Windows平台相机功能插件camera_windows的使用
Camera Windows Plugin
camera_windows是camera插件在Windows平台上的实现。请注意，该插件仍在开发中，某些特性可能尚未完全实现或存在限制。
使用方法
依赖包
由于camera_windows不是官方推荐的camera插件实现，因此除了依赖于camera外，还需要显式地将camera_windows添加到pubspec.yaml文件中。一旦添加了，就可以像平常一样使用camera API。
dependencies:
camera: ^0.10.5+3
camera_windows: ^0.2.0
Windows平台缺失的功能
- 设备方向：设备方向检测尚未实现。
- 暂停和恢复视频录制：由于Windows API的限制，不支持暂停和恢复视频录制。
- 曝光模式、点和偏移：曝光模式和偏移的支持尚未实现，曝光点也不受支持。
- 对焦模式和点：对焦模式和点的支持尚未实现。
- 闪光灯模式：闪光灯模式的支持尚未实现。
- 帧流：图像流的支持尚未实现。
错误处理
可以使用平台提供的onCameraError方法监听相机错误。在某些情况下，释放相机是唯一重置情况的方法。
示例代码
以下是一个完整的示例代码，展示了如何使用camera_windows插件来捕获照片和视频，并进行基本的相机控制。
import 'dart:async';
import 'package:camera_platform_interface/camera_platform_interface.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
String _cameraInfo = 'Unknown';
List<CameraDescription> _cameras = [];
int _cameraIndex = 0;
int _cameraId = -1;
bool _initialized = false;
bool _recording = false;
bool _recordingTimed = false;
bool _previewPaused = false;
Size? _previewSize;
MediaSettings _mediaSettings = const MediaSettings(
resolutionPreset: ResolutionPreset.low,
fps: 15,
videoBitrate: 200000,
audioBitrate: 32000,
enableAudio: true,
);
StreamSubscription<CameraErrorEvent>? _errorStreamSubscription;
StreamSubscription<CameraClosingEvent>? _cameraClosingStreamSubscription;
@override
void initState() {
super.initState();
WidgetsFlutterBinding.ensureInitialized();
_fetchCameras();
}
@override
void dispose() {
_disposeCurrentCamera();
_errorStreamSubscription?.cancel();
_cameraClosingStreamSubscription?.cancel();
super.dispose();
}
Future<void> _fetchCameras() async {
String cameraInfo;
List<CameraDescription> cameras = [];
int cameraIndex = 0;
try {
cameras = await CameraPlatform.instance.availableCameras();
if (cameras.isEmpty) {
cameraInfo = 'No available cameras';
} else {
cameraIndex = _cameraIndex % cameras.length;
cameraInfo = 'Found camera: ${cameras[cameraIndex].name}';
}
} on PlatformException catch (e) {
cameraInfo = 'Failed to get cameras: ${e.code}: ${e.message}';
}
if (mounted) {
setState(() {
_cameraIndex = cameraIndex;
_cameras = cameras;
_cameraInfo = cameraInfo;
});
}
}
Future<void> _initializeCamera() async {
assert(!_initialized);
if (_cameras.isEmpty) {
return;
}
int cameraId = -1;
try {
final int cameraIndex = _cameraIndex % _cameras.length;
final CameraDescription camera = _cameras[cameraIndex];
cameraId = await CameraPlatform.instance.createCameraWithSettings(
camera,
_mediaSettings,
);
unawaited(_errorStreamSubscription?.cancel());
_errorStreamSubscription = CameraPlatform.instance
.onCameraError(cameraId)
.listen(_onCameraError);
unawaited(_cameraClosingStreamSubscription?.cancel());
_cameraClosingStreamSubscription = CameraPlatform.instance
.onCameraClosing(cameraId)
.listen(_onCameraClosing);
final Future<CameraInitializedEvent> initialized =
CameraPlatform.instance.onCameraInitialized(cameraId).first;
await CameraPlatform.instance.initializeCamera(
cameraId,
);
final CameraInitializedEvent event = await initialized;
_previewSize = Size(
event.previewWidth,
event.previewHeight,
);
if (mounted) {
setState(() {
_initialized = true;
_cameraId = cameraId;
_cameraIndex = cameraIndex;
_cameraInfo = 'Capturing camera: ${camera.name}';
});
}
} on CameraException catch (e) {
try {
if (cameraId >= 0) {
await CameraPlatform.instance.dispose(cameraId);
}
} on CameraException catch (e) {
debugPrint('Failed to dispose camera: ${e.code}: ${e.description}');
}
if (mounted) {
setState(() {
_initialized = false;
_cameraId = -1;
_previewSize = null;
_recording = false;
_recordingTimed = false;
_cameraInfo =
'Failed to initialize camera: ${e.code}: ${e.description}';
});
}
}
}
Future<void> _disposeCurrentCamera() async {
if (_cameraId >= 0 && _initialized) {
try {
await CameraPlatform.instance.dispose(_cameraId);
if (mounted) {
setState(() {
_initialized = false;
_cameraId = -1;
_previewSize = null;
_recording = false;
_recordingTimed = false;
_previewPaused = false;
_cameraInfo = 'Camera disposed';
});
}
} on CameraException catch (e) {
if (mounted) {
setState(() {
_cameraInfo =
'Failed to dispose camera: ${e.code}: ${e.description}';
});
}
}
}
}
Widget _buildPreview() {
return CameraPlatform.instance.buildPreview(_cameraId);
}
Future<void> _takePicture() async {
final XFile file = await CameraPlatform.instance.takePicture(_cameraId);
_showInSnackBar('Picture captured to: ${file.path}');
}
Future<void> _recordTimed(int seconds) async {
if (_initialized && _cameraId > 0 && !_recordingTimed) {
unawaited(CameraPlatform.instance
.onVideoRecordedEvent(_cameraId)
.first
.then((VideoRecordedEvent event) async {
if (mounted) {
setState(() {
_recordingTimed = false;
});
_showInSnackBar('Video captured to: ${event.file.path}');
}
}));
await CameraPlatform.instance.startVideoRecording(
_cameraId,
maxVideoDuration: Duration(seconds: seconds),
);
if (mounted) {
setState(() {
_recordingTimed = true;
});
}
}
}
Future<void> _toggleRecord() async {
if (_initialized && _cameraId > 0) {
if (_recordingTimed) {
await CameraPlatform.instance.stopVideoRecording(_cameraId);
} else {
if (!_recording) {
await CameraPlatform.instance.startVideoRecording(_cameraId);
} else {
final XFile file =
await CameraPlatform.instance.stopVideoRecording(_cameraId);
_showInSnackBar('Video captured to: ${file.path}');
}
if (mounted) {
setState(() {
_recording = !_recording;
});
}
}
}
}
Future<void> _togglePreview() async {
if (_initialized && _cameraId >= 0) {
if (!_previewPaused) {
await CameraPlatform.instance.pausePreview(_cameraId);
} else {
await CameraPlatform.instance.resumePreview(_cameraId);
}
if (mounted) {
setState(() {
_previewPaused = !_previewPaused;
});
}
}
}
Future<void> _switchCamera() async {
if (_cameras.isNotEmpty) {
_cameraIndex = (_cameraIndex + 1) % _cameras.length;
if (_initialized && _cameraId >= 0) {
await _disposeCurrentCamera();
await _fetchCameras();
if (_cameras.isNotEmpty) {
await _initializeCamera();
}
} else {
await _fetchCameras();
}
}
}
Future<void> _onResolutionChange(ResolutionPreset newValue) async {
setState(() {
_mediaSettings = MediaSettings(
resolutionPreset: newValue,
fps: _mediaSettings.fps,
videoBitrate: _mediaSettings.videoBitrate,
audioBitrate: _mediaSettings.audioBitrate,
enableAudio: _mediaSettings.enableAudio,
);
});
if (_initialized && _cameraId >= 0) {
await _disposeCurrentCamera();
await _initializeCamera();
}
}
Future<void> _onAudioChange(bool recordAudio) async {
setState(() {
_mediaSettings = MediaSettings(
resolutionPreset: _mediaSettings.resolutionPreset,
fps: _mediaSettings.fps,
videoBitrate: _mediaSettings.videoBitrate,
audioBitrate: _mediaSettings.audioBitrate,
enableAudio: recordAudio,
);
});
if (_initialized && _cameraId >= 0) {
await _disposeCurrentCamera();
await _initializeCamera();
}
}
void _onCameraError(CameraErrorEvent event) {
if (mounted) {
_scaffoldMessengerKey.currentState?.showSnackBar(
SnackBar(content: Text('Error: ${event.description}')));
_disposeCurrentCamera();
_fetchCameras();
}
}
void _onCameraClosing(CameraClosingEvent event) {
if (mounted) {
_showInSnackBar('Camera is closing');
}
}
void _showInSnackBar(String message) {
_scaffoldMessengerKey.currentState?.showSnackBar(SnackBar(
content: Text(message),
duration: const Duration(seconds: 1),
));
}
final GlobalKey<ScaffoldMessengerState> _scaffoldMessengerKey =
GlobalKey<ScaffoldMessengerState>();
@override
Widget build(BuildContext context) {
final List<DropdownMenuItem<ResolutionPreset>> resolutionItems =
ResolutionPreset.values
.map<DropdownMenuItem<ResolutionPreset>>((ResolutionPreset value) {
return DropdownMenuItem<ResolutionPreset>(
value: value,
child: Text(value.toString()),
);
}).toList();
return MaterialApp(
scaffoldMessengerKey: _scaffoldMessengerKey,
home: Scaffold(
appBar: AppBar(
title: const Text('Plugin example app'),
),
body: ListView(
children: [
Padding(
padding: const EdgeInsets.symmetric(vertical: 5, horizontal: 10),
child: Text(_cameraInfo),
),
if (_cameras.isEmpty)
ElevatedButton(
onPressed: _fetchCameras,
child: const Text('Re-check available cameras'),
),
if (_cameras.isNotEmpty)
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
DropdownButton<ResolutionPreset>(
value: _mediaSettings.resolutionPreset,
onChanged: (ResolutionPreset? value) {
if (value != null) {
_onResolutionChange(value);
}
},
items: resolutionItems,
),
const SizedBox(width: 20),
const Text('Audio:'),
Switch(
value: _mediaSettings.enableAudio,
onChanged: (bool state) => _onAudioChange(state)),
const SizedBox(width: 20),
ElevatedButton(
onPressed: _initialized
? _disposeCurrentCamera
: _initializeCamera,
child: Text(_initialized ? 'Dispose camera' : 'Create camera'),
),
const SizedBox(width: 5),
ElevatedButton(
onPressed: _initialized ? _takePicture : null,
child: const Text('Take picture'),
),
const SizedBox(width: 5),
ElevatedButton(
onPressed: _initialized ? _togglePreview : null,
child: Text(
_previewPaused ? 'Resume preview' : 'Pause preview',
),
),
const SizedBox(width: 5),
ElevatedButton(
onPressed: _initialized ? _toggleRecord : null,
child: Text(
(_recording || _recordingTimed)
? 'Stop recording'
: 'Record Video',
),
),
const SizedBox(width: 5),
ElevatedButton(
onPressed: (_initialized && !_recording && !_recordingTimed)
? () => _recordTimed(5)
: null,
child: const Text(
'Record 5 seconds',
),
),
if (_cameras.length > 1) ...[
const SizedBox(width: 5),
ElevatedButton(
onPressed: _switchCamera,
child: const Text(
'Switch camera',
),
),
]
],
),
const SizedBox(height: 5),
if (_initialized && _cameraId > 0 && _previewSize != null)
Padding(
padding: const EdgeInsets.symmetric(vertical: 10),
child: Align(
child: Container(
constraints: const BoxConstraints(maxHeight: 500),
child: AspectRatio(
aspectRatio: _previewSize!.width / _previewSize!.height,
child: _buildPreview(),
),
),
),
),
if (_previewSize != null)
Center(
child: Text(
'Preview size: ${_previewSize!.width.toStringAsFixed(0)}x${_previewSize!.height.toStringAsFixed(0)}',
),
),
],
),
),
);
}
}
这个示例展示了如何初始化相机、切换摄像头、调整分辨率、开启/关闭音频、拍照、录制视频以及暂停/恢复预览等功能。请根据实际需求进行调整和优化。
更多关于Flutter Windows平台相机功能插件camera_windows的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html
1 回复
更多关于Flutter Windows平台相机功能插件camera_windows的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html
在Flutter中，camera_windows 插件允许你在Windows平台上使用相机功能。以下是一个如何使用 camera_windows 插件的基本示例代码。
1. 添加依赖
首先，你需要在 pubspec.yaml 文件中添加 camera 和 camera_windows 依赖：
dependencies:
flutter:
sdk: flutter
camera: ^0.10.0+1 # 请确保使用最新版本
dependency_overrides:
camera_platform_interface: ^2.2.0 # 如果需要覆盖以解决兼容性问题
camera_windows: ^0.2.0+4 # 请确保使用最新版本
2. 配置插件
在 windows 文件夹下的 CMakeLists.txt 文件中，添加对 camera_windows 插件的支持（如果文件不存在，请创建它）：
cmake_minimum_required(VERSION 3.10)
# 添加对camera_windows插件的支持
add_subdirectory(plugins/camera_windows/windows)
3. 使用相机功能
以下是一个简单的 Flutter 应用示例，展示如何使用相机插件来捕获和显示相机预览：
import 'package:flutter/material.dart';
import 'package:camera/camera.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Camera Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: CameraApp(),
);
}
}
class CameraApp extends StatefulWidget {
@override
_CameraAppState createState() => _CameraAppState();
}
class _CameraAppState extends State<CameraApp> {
CameraController? controller;
final List<CameraDescription> cameras = [];
@override
void initState() {
super.initState();
availableCameras().then((availableCameras) {
cameras.addAll(availableCameras);
if (cameras.isEmpty) {
print('No cameras found');
return;
}
// 使用第一个相机
controller = CameraController(cameras[0], ResolutionPreset.medium);
controller!.initialize().then((_) {
if (!mounted) {
return;
}
setState(() {});
});
}).catchError((err) {
print('Error: ${err.code}\n${err.message}');
});
}
@override
void dispose() {
controller?.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
if (controller == null || !controller!.value.isInitialized) {
return Container();
}
return Scaffold(
appBar: AppBar(
title: Text('Camera Demo'),
),
body: Center(
child: CameraPreview(controller!),
),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.camera_alt),
onPressed: () async {
try {
final XFile? image = await controller!.takePicture();
if (image != null) {
// 显示或保存图片
print(image.path);
}
} catch (e) {
print(e);
}
},
),
);
}
}
4. 运行应用
确保你的开发环境已经配置好 Flutter 和 Windows 开发工具链，然后运行应用：
flutter run -d windows
这段代码展示了如何在 Flutter Windows 应用中使用 camera_windows 插件来初始化相机、显示相机预览以及拍照。请注意，这只是一个基础示例，实际应用中你可能需要处理更多的错误情况、优化性能和用户体验等。
