Flutterpermission_handler 检查之前是否请求过权限

Question

我正在使用工作正常的permission_handler，但现在我需要知道某个

Permission

之前是否已经是

requested

。

所以我正在寻找类似

PermissionStatus.notDetermined

的东西。这个套餐提供类似的东西吗？我找不到它，但至少对我来说这是一件非常重要的事情。

我知道

firebase_messaging

包中有类似的东西。

如果之前未请求过 systemPermissionStatus，我只想显示一个弹出窗口。

这当然也可以通过在

SharedPreferences

中保存一些值来完成，例如“wasRequested”，但我认为这个用例必须有一个现有的函数？

如果您需要更多信息，请告诉我。

更新

我还注意到

status

和从

status

返回的

.request

是不同的。

这对我来说没有任何意义，这太令人困惑了。

final stat = await Permission.notification.status; // -> denied
final req = await Permission.notification.request(); // -> permanentlyDenied

Answer 1

您可以在文档的如何使用部分中看到第一个示例，它使用

Permission.camera.status.isDenied

来确定权限是否被拒绝或尚未询问。代码注释中这么说：

if (status.isDenied) {
  // We haven't asked for permission yet or the permission has been denied before, but not permanently.
}

所以您可以使用

isDenied

作为您的

notDetermined

。

我提供了使用

isDenied

来调节弹出窗口的示例代码

import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';

class PermissionHandlerPage extends StatefulWidget {
  const PermissionHandlerPage({super.key});

  @override
  State<PermissionHandlerPage> createState() => _PermissionHandlerPageState();
}

class _PermissionHandlerPageState extends State<PermissionHandlerPage> {
  String status = '-';

  void _showRequestPermissionDialog() {
    AlertDialog alert(BuildContext context) {
      Widget title = const Text('Permission');

      Widget content = const Text(
        'This application need location permission to run.',
      );

      Widget cancel = OutlinedButton(
        onPressed: () => Navigator.pop(context),
        child: const Text('Cancel'),
      );

      Future<void> handleRequest() async {
        // Request [locationWhenInUse] permission.
        final status = await Permission.locationWhenInUse.request();
        this.status = status.name;
        setState(() {});
      }

      Widget request = ElevatedButton(
        onPressed: handleRequest,
        child: const Text('Request Permission'),
      );

      return AlertDialog(
        title: title,
        content: content,
        actions: [cancel, request],
      );
    }

    showDialog(context: context, builder: alert);
  }

  Future<void> _checkPermission() async {
    final status = await Permission.location.status;

    if (status.isDenied) {
      // [Permission.location.status] As per official documentation:
      // "We haven't asked for permission yet or the permission has been
      // denied before, but not permanently."
      //
      // https://pub.dev/packages/permission_handler
      print('Permission is denied or not asked yet.');

      // Show dialog to inform user that permission not granted yet.
      _showRequestPermissionDialog();
    } else if (status.isPermanentlyDenied) {
      print('Permission is permanently denied');
    } else if (status.isGranted) {
      print('Permission granted');
    }

    this.status = status.name;
    setState(() {});
  }

  @override
  void initState() {
    super.initState();

    // Check permission at the first time page opened.
    _checkPermission();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Permission Handler')),
      body: SafeArea(
        child: Center(
          child: Text('Permission status: $status'),
        ),
      ),
    );
  }
}