Question

我正在开发一个使用位置数据的应用。因此，在登陆屏幕中，我将检查是否授予访问位置数据的权限。我使用 geolocator 包来做到这一点。当用户授予权限时，我会收集当前位置等数据，然后我想自动移动到另一个屏幕，即应用程序的主屏幕。有什么办法可以做到这一点吗？

Answer 1

如果您希望主屏幕取决于值或条件，我认为您可以在家中简单地使用 Streambuilder，其 streamcontroller 接收一个布尔值，取决于它会返回一个屏幕或其他。

例如，我在这里使用了这个 Streambuilder 来监听布尔值。我将通过按下按钮将此布尔值的值更改为 true。在我家的 Streambuilder 中，我的条件是，如果收到的信息 snapshot.data 为真，那么它不应该返回 MyHomePage，而是返回 TheOtherRoute。

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

void main() {
  runApp(MyApp());
}

final StreamController<bool> _streamController =
    StreamController<bool>.broadcast();

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: StreamBuilder(
        stream: _streamController.stream,
        builder: (context, snapshot) {
            if(snapshot.data == true){
              return TheOtherRoute();
            }
          return MyHomePage();
        },
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('this is a testo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              child: FlatButton(
                color: Colors.black38,
                child: Text('Change boolean'),
                onPressed: () {
                  _streamController.add(true);
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class FirstRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('First Route'),
      ),
      body: Center(
        child: Text('Your boolean changed. Your home page is now FirstRoute()'),
      ),
    );
  }
}

试试看告诉我。

Answer 2

我正在制作一个简单的应用程序来演示基于结果的权限检查和导航的正确处理。您可以查看以下代码和注释以了解流程：

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: SomeScreen(),
    );
  }
}

class SomeScreen extends StatelessWidget {
  final _scaffoldKey = GlobalKey<ScaffoldState>();

  void _determinePosition(context) async {
    bool serviceEnabled;
    LocationPermission permission;
    serviceEnabled = await Geolocator.isLocationServiceEnabled();
    
    // Checking if the service is enabled
    if (!serviceEnabled) {
      // If not, display a Snackbar
      _scaffoldKey.currentState.showSnackBar(SnackBar(
        content: Text('Location services are disabled.'),
        duration: Duration(seconds: 2),
      ));
    }

    // Checking the permission here
    permission = await Geolocator.checkPermission();
    if (permission == LocationPermission.denied) {
      permission = await Geolocator.requestPermission();
      if (permission == LocationPermission.deniedForever) {
        _scaffoldKey.currentState.showSnackBar(SnackBar(
          content: Text(
              'Location permissions are permanently denied, we cannot request permissions.'),
          duration: Duration(seconds: 2),
        ));
      }

      if (permission == LocationPermission.denied) {
        _scaffoldKey.currentState.showSnackBar(SnackBar(
          content: Text('Location permissions are denied'),
          duration: Duration(seconds: 2),
        ));
      }
    }

    // Finally if the permission is granted, navigate the user to new screen
    Position position = await Geolocator.getCurrentPosition();
    Navigator.push(context,
        MaterialPageRoute(builder: (context) => Home(position: position)));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      body: Container(
        alignment: Alignment.center,
        color: Colors.blue,
        child: FlatButton(
          onPressed: () => _determinePosition(context),
          child: Text("Check permission"),
          color: Colors.red,
        ),
      ),
    );
  }
}

//  A simple screen to display the position
class Home extends StatefulWidget {
  final Position position;

  Home({this.position});

  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: Center(
          child: Text(
              'Location: ${widget.position.altitude} ${widget.position.longitude}'),
        ),
      ),
    );
  }
}

自动浏览颤动屏幕

2 个答案: