flutter-使用permission_handler进行系统权限的申请和操作

import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PermissionPage(),
    );
  }
}
 
class PermissionPage extends StatefulWidget {
  @override
  _PermissionPageState createState() => _PermissionPageState();
}
 
class _PermissionPageState extends State<PermissionPage> {
  PermissionStatus _permissionStatus = PermissionStatus.denied;
 
  Future<void> checkPermission() async {
    final PermissionStatus permissionStatus = await Permission.camera.status;
    setState(() {
      _permissionStatus = permissionStatus;
    });
  }
 
  Future<void> requestPermission() async {
    final PermissionStatus permissionStatus = await Permission.camera.request();
    setState(() {
      _permissionStatus = permissionStatus;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Permission Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Camera permission status: $_permissionStatus\n'),
            RaisedButton(
              child: Text('Check permission status'),
              onPressed: checkPermission,
            ),
            RaisedButton(
              child: Text('Request permission'),
              onPressed: requestPermission,
            ),
          ],
        ),
      ),
    );
  }
}

这段代码演示了如何在Flutter应用中使用permission_handler插件来检查和请求相机权限。代码首先定义了一个_PermissionPageState状态类，其中包含了检查和请求权限的异步函数。在build方法中，它创建了两个按钮，分别用于触发这些函数。这个例子简单明了，对开发者有很好的指导作用。