前言

简单学习一下几个比较好用的文件读取库

video_player

简介
用于视频播放

官方文档
https://pub-web.flutter-io.cn/packages/video_player

安装

flutter pub add video_player

加载网络视频

class _MyHomePageState extends State<MyHomePage> {// 控制器late VideoPlayerController _controller;// 初始化@overridevoid initState() {super.initState();// 加载网络视频_controller = VideoPlayerController.networkUrl(Uri.parse('https://www.tujuyun.com/pixabay/video/VideoBig/1024927/4006.mp4'))..initialize().then((_) {setState(() {});});}@overridevoid dispose() {super.dispose();_controller.dispose();}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: _controller.value.isInitialized // 判断是否已经加载完成? AspectRatio(// 设置视频播放的宽高比aspectRatio: _controller.value.aspectRatio,child: VideoPlayer(_controller),): Container(),),floatingActionButton: FloatingActionButton(onPressed: () {setState(() {_controller.value.isPlaying // 判断是否是在播放中? _controller.pause() //暂停: _controller.play(); // 播放});},child: Icon(_controller.value.isPlaying ? Icons.pause : Icons.play_arrow,),),);}
}

加载本地视频

   _controller = VideoPlayerController.asset('lib/assets/video/3998.mp4')..initialize().then((_) {setState(() {});});

设置倍速和进度条

Center(child: _controller.value.isInitialized // 判断是否已经加载完成? AspectRatio(// 设置视频播放的宽高比aspectRatio: _controller.value.aspectRatio,child: Stack(alignment: Alignment.bottomCenter,children: <Widget>[// 视频播放器VideoPlayer(_controller),// 设置倍速Row(children: [ElevatedButton(onPressed: () {_controller.setPlaybackSpeed(1);},child: const Text("1倍速")),ElevatedButton(onPressed: () {_controller.setPlaybackSpeed(5);},child: const Text("5倍速"))],),// 视频的进度条VideoProgressIndicator(_controller, allowScrubbing: true),],),): Container(),)

chewie

video_player虽然是官方提供的插件，但是很明显它只适合拿来简单的播放视频，就比如前端的video标签功能也很少。在这里推荐一下chewie

简介

chewie是基于video_player实现的，它额外提供了很多功能，比如：倍速、进度条、全屏以及其他的功能

官方文档
https://pub-web.flutter-io.cn/packages/chewie

安装

flutter pub add chewie

默认的弹出菜单是这样的

可以通过设置optionsBuilder来进行自定义显示

class MyHomePage extends StatefulWidget {const MyHomePage({super.key, required this.title});final String title;@overrideState<MyHomePage> createState() => _MyHomePageState();
}class _MyHomePageState extends State<MyHomePage> {// 控制器late VideoPlayerController _controller;late ChewieController _chewieController;late PersistentBottomSheetController<dynamic> _bottomSheetController;// 初始化@overridevoid initState() {super.initState();// 加载网络视频_controller = VideoPlayerController.networkUrl(Uri.parse('https://www.tujuyun.com/pixabay/video/VideoBig/1024927/4006.mp4'))..initialize().then((_) {setState(() {});_chewieController = ChewieController(videoPlayerController: _controller,autoPlay: true,looping: true,optionsBuilder: (context, defaultOptions) async {// 这里面现在是只有一个设置倍速的，我们把它拿出来// for (int i = 0; i < defaultOptions.length; i++) {//   print("默认选项：${defaultOptions[i]}");// }// await showDialog<void>(//   context: context,//   builder: (ctx) {//     // return AlertDialog(//     //   content: ListView.builder(//     //     itemCount: defaultOptions.length,//     //     itemBuilder: (_, i) => ActionChip(//     //       label: Text(defaultOptions[i].title),//     //       onPressed: () => defaultOptions[i].onTap!(),//     //     ),//     //   ),//     // );//   },// );_bottomSheetController =Scaffold.of(context).showBottomSheet((BuildContext context) {return SizedBox(height: 200,child: ListView(children: <Widget>[ListTile(leading: const Icon(Icons.speed),title: const Text('倍速'),onTap: () => defaultOptions[0].onTap!(),),const Divider(color: Colors.grey,thickness: 1.0,),ListTile(leading: const Icon(Icons.download),title: const Text('下载'),onTap: () => print("下载中.."),),const Divider(color: Colors.grey,thickness: 1.0,),ListTile(leading: const Icon(Icons.close),title: const Text('关闭'),onTap: () => _bottomSheetController.close(),),],),);});},);});}@overridevoid dispose() {super.dispose();_controller.dispose();_chewieController.dispose();}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: _controller.value.isInitialized // 判断是否已经加载完成? AspectRatio(// 设置视频播放的宽高比aspectRatio: _controller.value.aspectRatio,child: Chewie(controller: _chewieController,),): Container(),),);}
}

注： chewie 还有很多其他高级功能，比如自定义UI界面、设置弹幕等。需要好好看一下官方文档，才能实现高级功能，不过上面那个例子已经可以满足基本的使用了。

image_picker

简介
用于从相册中挑选图片、视频、使用相机拍摄照片。

官方文档
https://pub-web.flutter-io.cn/packages/image_picker

安装

flutter pub add image_picker

示例：读取单张图片

class _MyHomePageState extends State<MyHomePage> {// 图片文件File? _image;// 错误信息String _error = '';// 图片选择函数Future<void> _pickImage() async {// 从相册中选择图片try {final pickedImage =await ImagePicker().pickImage(source: ImageSource.gallery);if (pickedImage != null) {setState(() {_image = File(pickedImage.path);});}} catch (e) {setState(() {_error = e.toString();});}}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [// 图片存在则显示if (_image != null)Image.file(_image!,width: 200,height: 200,),// 如果错误信息存在if (_error.isNotEmpty) Text("错误：$_error"),const SizedBox(height: 20,),ElevatedButton(onPressed: _pickImage, child: const Text("从相册里选取图片"))],),),);}
}

看了一下好像不能设置选择的图片格式，只能设置大小、质量

如果设置为ImagePicker().pickImage(source: ImageSource.camera) ，这是调用摄像头来进行获取图片

示例：读取多张图片

class _MyHomePageState extends State<MyHomePage> {// 图片文件列表final List<File> _pickedFileList = [];// 错误信息String _error = '';// 图片选择函数Future<void> _pickImage() async {// 从相册中选择图片try {final pickedImageList = await ImagePicker().pickMultiImage();if (pickedImageList.isNotEmpty) {for (XFile image in pickedImageList) {_pickedFileList.add(File(image.path));}setState(() {});}} catch (e) {setState(() {_error = e.toString();});}}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [Expanded(child: ListView.builder(itemCount: _pickedFileList.length,itemBuilder: (context, index) {return Image.file(_pickedFileList[index],width: 200,height: 200,);})),// 如果错误信息存在if (_error.isNotEmpty) Text("错误：$_error"),const SizedBox(height: 20,),ElevatedButton(onPressed: _pickImage, child: const Text("从相册里选取图片"))],),),);}
}

要长按图片，才能够一次选择多个，最后在点击右上角的选择。轻触会直接选中图片。另外看了下pickMultiImage里的入参好像不支持限制图片的个数

示例：选择单个视频

选择视频稍微复杂一点，还需要借助video_player等插件才能更进行预览。

class _MyHomePageState extends State<MyHomePage> {// 错误信息String _error = '';// 视频信息late File _video;// 视频播放器VideoPlayerController? _videoPlayerController;Future<void>? _videoPlayerInitializer;// 选择视频Future<void> _pickVideo() async {// 从相册中选择视频try {final pickedVideo =await ImagePicker().pickVideo(source: ImageSource.gallery);if (pickedVideo != null) {setState(() {_video = File(pickedVideo.path);_videoPlayerController = VideoPlayerController.file(_video);_videoPlayerInitializer = _videoPlayerController!.initialize();// 播放视频_videoPlayerController!.play();});}} catch (e) {setState(() {_error = e.toString();});}}@overridevoid dispose() {_videoPlayerController?.dispose();super.dispose();}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [if (_videoPlayerController != null)FutureBuilder(future: _videoPlayerInitializer,builder: (BuildContext context, AsyncSnapshot<void> snapshot) {if (snapshot.connectionState == ConnectionState.done) {return SizedBox(width: 300,height: 200,child: AspectRatio(aspectRatio:1.5,child: VideoPlayer(_videoPlayerController!),),);} else {return const CircularProgressIndicator();}},),// 如果错误信息存在if (_error.isNotEmpty) Text("错误：$_error"),const SizedBox(height: 20,),ElevatedButton(onPressed: _pickVideo, child: const Text("从相册里选取视频"))],),),);}
}

file_picker

简介
一个包，允许您使用本机文件资源管理器来选择单个或多个文件，具有扩展筛选支持。

官方文档
https://pub-web.flutter-io.cn/packages/file_picker

安装

flutter pub add file_picker

示例：选择单个文件

class _MyHomePageState extends State<MyHomePage> {// 错误信息String _error = '';// 文件路径String _filePath = '';// 选择文件Future _pickFile() async {try {FilePickerResult? result = await FilePicker.platform.pickFiles(dialogTitle: "选择图片",type: FileType.image, // 设置文件的类型);if (result != null) {setState(() {_filePath = result.files.single.path!;});}} catch (e) {setState(() {_error = e.toString();});}}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [// File 是 io包下的_filePath == '' ? const Text("未选择文件") : Image.file(File(_filePath)),// 如果错误信息存在if (_error.isNotEmpty) Text("错误：$_error"),const SizedBox(height: 20,),ElevatedButton(onPressed: _pickFile, child: const Text("选择一个图片"))],),),);}
}

示例：选择多个文件

FilePickerResult? result = await FilePicker.platform.pickFiles(allowMultiple: true);if (result != null) {List<File> files = result.paths.map((path) => File(path)).toList();
} else {// User canceled the picker
}

其他功能略，可以自行查看官方文档