Flutter 如何判断给定的路径是图像还是视频

请使用套餐https://pub.dev/packages/mime
扩展和MIME类型映射 https://github.com/dart-lang/mime/blob/master/lib/src/default_extension_map.dart
video/*表示视频，image/*表示图像

代码片段

String mimeStr = lookupMimeType(_path);
var fileType = mimeStr.split('/');
print('file type ${fileType}');

完整代码，文件 Select 器演示添加判断mime类型的函数_openFileExplorer()

import 'package:flutter/material.dart';

import 'package:flutter/services.dart';
import 'package:file_picker/file_picker.dart';
import 'package:mime/mime.dart';

class FilePickerDemo extends StatefulWidget {
  @override
  _FilePickerDemoState createState() => new _FilePickerDemoState();
}

class _FilePickerDemoState extends State<FilePickerDemo> {
  String _fileName;
  String _path;
  Map<String, String> _paths;
  String _extension;
  bool _loadingPath = false;
  bool _multiPick = false;
  bool _hasValidMime = false;
  FileType _pickingType;
  TextEditingController _controller = new TextEditingController();

  @override
  void initState() {
    super.initState();
    _controller.addListener(() => _extension = _controller.text);
  }

  void _openFileExplorer() async {
    if (_pickingType != FileType.CUSTOM || _hasValidMime) {
      setState(() => _loadingPath = true);
      try {
        if (_multiPick) {
          _path = null;
          _paths = await FilePicker.getMultiFilePath(
              type: _pickingType, fileExtension: _extension);
        } else {
          _paths = null;
          _path = await FilePicker.getFilePath(
              type: _pickingType, fileExtension: _extension);

          String mimeStr = lookupMimeType(_path);
          var fileType = mimeStr.split('/');
          print('file type ${fileType}');
        }
      } on PlatformException catch (e) {
        print("Unsupported operation" + e.toString());
      }
      if (!mounted) return;
      setState(() {
        _loadingPath = false;
        _fileName = _path != null
            ? _path.split('/').last
            : _paths != null ? _paths.keys.toString() : '...';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: const Text('File Picker example app'),
        ),
        body: new Center(
            child: new Padding(
          padding: const EdgeInsets.only(left: 10.0, right: 10.0),
          child: new SingleChildScrollView(
            child: new Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                new Padding(
                  padding: const EdgeInsets.only(top: 20.0),
                  child: new DropdownButton(
                      hint: new Text('LOAD PATH FROM'),
                      value: _pickingType,
                      items: <DropdownMenuItem>[
                        new DropdownMenuItem(
                          child: new Text('FROM AUDIO'),
                          value: FileType.AUDIO,
                        ),
                        new DropdownMenuItem(
                          child: new Text('FROM IMAGE'),
                          value: FileType.IMAGE,
                        ),
                        new DropdownMenuItem(
                          child: new Text('FROM VIDEO'),
                          value: FileType.VIDEO,
                        ),
                        new DropdownMenuItem(
                          child: new Text('FROM ANY'),
                          value: FileType.ANY,
                        ),
                        new DropdownMenuItem(
                          child: new Text('CUSTOM FORMAT'),
                          value: FileType.CUSTOM,
                        ),
                      ],
                      onChanged: (value) => setState(() {
                            _pickingType = value;
                            if (_pickingType != FileType.CUSTOM) {
                              _controller.text = _extension = '';
                            }
                          })),
                ),
                new ConstrainedBox(
                  constraints: BoxConstraints.tightFor(width: 100.0),
                  child: _pickingType == FileType.CUSTOM
                      ? new TextFormField(
                          maxLength: 15,
                          autovalidate: true,
                          controller: _controller,
                          decoration:
                              InputDecoration(labelText: 'File extension'),
                          keyboardType: TextInputType.text,
                          textCapitalization: TextCapitalization.none,
                          validator: (value) {
                            RegExp reg = new RegExp(r'[^a-zA-Z0-9]');
                            if (reg.hasMatch(value)) {
                              _hasValidMime = false;
                              return 'Invalid format';
                            }
                            _hasValidMime = true;
                            return null;
                          },
                        )
                      : new Container(),
                ),
                new ConstrainedBox(
                  constraints: BoxConstraints.tightFor(width: 200.0),
                  child: new SwitchListTile.adaptive(
                    title: new Text('Pick multiple files',
                        textAlign: TextAlign.right),
                    onChanged: (bool value) =>
                        setState(() => _multiPick = value),
                    value: _multiPick,
                  ),
                ),
                new Padding(
                  padding: const EdgeInsets.only(top: 50.0, bottom: 20.0),
                  child: new RaisedButton(
                    onPressed: () => _openFileExplorer(),
                    child: new Text("Open file picker"),
                  ),
                ),
                new Builder(
                  builder: (BuildContext context) => _loadingPath
                      ? Padding(
                          padding: const EdgeInsets.only(bottom: 10.0),
                          child: const CircularProgressIndicator())
                      : _path != null || _paths != null
                          ? new Container(
                              padding: const EdgeInsets.only(bottom: 30.0),
                              height: MediaQuery.of(context).size.height * 0.50,
                              child: new Scrollbar(
                                  child: new ListView.separated(
                                itemCount: _paths != null && _paths.isNotEmpty
                                    ? _paths.length
                                    : 1,
                                itemBuilder: (BuildContext context, int index) {
                                  final bool isMultiPath =
                                      _paths != null && _paths.isNotEmpty;
                                  final String name = 'File $index: ' +
                                      (isMultiPath
                                          ? _paths.keys.toList()[index]
                                          : _fileName ?? '...');
                                  final path = isMultiPath
                                      ? _paths.values.toList()[index].toString()
                                      : _path;

                                  return new ListTile(
                                    title: new Text(
                                      name,
                                    ),
                                    subtitle: new Text(path),
                                  );
                                },
                                separatorBuilder:
                                    (BuildContext context, int index) =>
                                        new Divider(),
                              )),
                            )
                          : new Container(),
                ),
              ],
            ),
          ),
        )),
      ),
    );
  }
}

演示输出

I/flutter (21426): file type [image, png]

个