权限处理程序颤动多个权限错误

Posted 2023-02-19

【中文标题】权限处理程序颤动多个权限错误

【英文标题】：Permission Handler flutter multiple permissions error

【发布时间】：2021-11-28 16:50:18

【问题描述】：

我正在尝试添加两个权限，即存储和摄像头。我已经在 androidmanifest.xml 文件中完成了所需的设置，并且在 main.dart 中使用 switch 调用了这两个请求。它给出了错误，但应用程序可以正常工作并且权限也会更新

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:get_storage/get_storage.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:firebase_core/firebase_core.dart';

import 'package:teamup/Connectivity/network_binding.dart';
import 'package:teamup/Views/Login/sign_in.dart';
import 'package:teamup/Views/OnboardingScreen/onboarding_screen.dart';
import 'Views/OnboardingScreen/onboarding_constants.dart';

void main() async 
  await GetStorage.init();
  WidgetsFlutterBinding.ensureInitialized();
  runApp(const MyApp());


class MyApp extends StatefulWidget 
  const MyApp(Key? key) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();


class _MyAppState extends State<MyApp> 
  late Permission cameraPermission;
  late Permission storagePermission;
  PermissionStatus cameraPermissionStatus = PermissionStatus.denied;
  PermissionStatus storagePermissionStatus = PermissionStatus.denied;

  void _listenForPermission() async 
    final cameraStatus = await Permission.camera.status;
    final storageStatus = await Permission.storage.status;
    setState(() 
      cameraPermissionStatus = cameraStatus;
      storagePermissionStatus = storageStatus;
    );

    switch (cameraStatus) 
      case PermissionStatus.denied:
        requestForPermission();
        break;
      case PermissionStatus.granted:
        break;
      case PermissionStatus.restricted:
        Navigator.pop(context);
        break;
      case PermissionStatus.limited:
        Navigator.pop(context);
        break;
      case PermissionStatus.permanentlyDenied:
        Navigator.pop(context);
        break;
    

    switch (storageStatus) 
      case PermissionStatus.denied:
        requestForPermission();
        break;
      case PermissionStatus.granted:
        break;
      case PermissionStatus.restricted:
        Navigator.pop(context);
        break;
      case PermissionStatus.limited:
        Navigator.pop(context);
        break;
      case PermissionStatus.permanentlyDenied:
        Navigator.pop(context);
        break;
    
  

  Future<void> requestForPermission() async 
    final cameraStatus = await Permission.camera.request();
    final storageStatus = await Permission.storage.request();
    setState(() 
      cameraPermissionStatus = cameraStatus;
      storagePermissionStatus = storageStatus;
    );
  

  @override
  void initState() 
    super.initState();
    _listenForPermission();
    isViewed.writeIfNull('key', 0);
    print(isViewed.read('key'));
  

  @override
  Widget build(BuildContext context) 
    return GetMaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(primarySwatch: Colors.blue, fontFamily: 'Glory'),
      initialBinding: NetworkBinding() ,
      home: isViewed.read('key') != 0
          ? const SignInPage()
          : const OnboardingPage(),
    );
  

这是安装后显示的消息

Launching lib\main.dart on Redmi Note 4 in debug mode...
Running Gradle task 'assembleDebug'...
√  Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...
W/FlutterActivityAndFragmentDelegate(21677): A splash screen was provided to Flutter, but this is deprecated. See flutter.dev/go/android-splash-migration for migration steps.
Debug service listening on ws://127.0.0.1:56092/dh3Yn3XCkGg=/ws
Syncing files to device Redmi Note 4...
I/FA      (21677): Tag Manager is not found and thus will not be used
I/flutter (21677): 0
[GETX] Instance "GetMaterialController" has been created
[GETX] Instance "GetMaterialController" has been initialized
[GETX] Instance "GetXNetworkManager" has been created
[GETX] Instance "GetXNetworkManager" has been initialized
I/Timeline(21677): Timeline: Activity_launch_request time:267480997 intent:Intent  act=android.content.pm.action.REQUEST_PERMISSIONS pkg=com.google.android.packageinstaller (has extras) 
E/flutter (21677): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: PlatformException(PermissionHandler.PermissionManager, A request for permissions is already running, please wait for it to finish before doing another request (note that you can request multiple permissions at the same time)., null, null)
E/flutter (21677): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:607:7)
E/flutter (21677): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:156:18)
E/flutter (21677): <asynchronous suspension>
E/flutter (21677): #2      MethodChannelPermissionHandler.requestPermissions (package:permission_handler_platform_interface/src/method_channel/method_channel_permission_handler.dart:71:9)
E/flutter (21677): <asynchronous suspension>
E/flutter (21677): #3      PermissionActions.request (package:permission_handler/permission_handler.dart:44:31)
E/flutter (21677): <asynchronous suspension>
E/flutter (21677): #4      _MyAppState.requestForPermission (package:teamup/main.dart:75:26)
E/flutter (21677): <asynchronous suspension>
E/flutter (21677): 
I/Timeline(21677): Timeline: Activity_launch_request time:267501469 intent:Intent  act=android.content.pm.action.REQUEST_PERMISSIONS pkg=com.google.android.packageinstaller (has extras) 

【参考方案1】：

_listenForPermission 中的 switch 语句将调用 requestForPermission 两次，如果 cameraStatus 和 storageStatus 的状态为 PermissionStatus.denied。因此你得到了例外：

PlatformException(PermissionHandler.PermissionManager, A request for permissions is already running, please wait for it to finish before doing another request (note that you can request multiple permissions at the same time)., null, null)

permission_handler package 允许您在一次调用中请求多个权限，如下所示：

// You can request multiple permissions at once.
Map<Permission, PermissionStatus> statuses = await [
  Permission.location,
  Permission.storage,
].request();
print(statuses[Permission.location]);