Flutter指南针功能插件dchs_flutter_compass的使用

dchs_flutter_compass

一个用于Flutter应用的指南针插件。指南针的方向值范围从0到360度，0表示北方向。

注意：

• Android Only: 当设备上没有可用传感器时，返回的方向值为null。

使用方法

要使用此插件，在pubspec.yaml文件中添加dchs_flutter_compass依赖项。例如：

dependencies:
  dchs_flutter_compass: '^1.0.0'

iOS

确保在Info.plist文件中添加以下键，并附上适当的描述：

• NSLocationWhenInUseUsageDescription
• NSLocationAlwaysAndWhenInUseUsageDescription

Android

确保在app/src/main/AndroidManifest.xml文件中添加以下权限：

• android.permission.INTERNET
• android.permission.ACCESS_COARSE_LOCATION
• android.permission.ACCESS_FINE_LOCATION

推荐支持插件

推荐使用Flutter Permission handler Plugin，它是一个跨平台（iOS, Android）的API，便于请求和检查权限。

完整示例代码

以下是使用dchs_flutter_compass插件的完整示例代码。

import 'dart:math' as math;

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

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

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

  [@override](/user/override)
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _hasPermissions = false;
  CompassEvent? _lastRead;
  DateTime? _lastReadAt;

  [@override](/user/override)
  void initState() {
    super.initState();

    // 获取权限状态
    _fetchPermissionStatus();
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.white,
        appBar: AppBar(
          title: const Text('Dchs Flutter 指南针'),
        ),
        body: Builder(builder: (context) {
          if (_hasPermissions) {
            return Column(
              children: [
                _buildManualReader(), // 手动读取指南针值
                Expanded(child: _buildCompass()), // 实时显示指南针
              ],
            );
          } else {
            return _buildPermissionSheet(); // 请求权限
          }
        }),
      ),
    );
  }

  Widget _buildManualReader() {
    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: Row(
        children: [
          ElevatedButton(
            child: Text('读取值'),
            onPressed: () async {
              final CompassEvent tmp = await FlutterCompass.events!.first;
              setState(() {
                _lastRead = tmp;
                _lastReadAt = DateTime.now();
              });
            },
          ),
          Expanded(
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    '$_lastRead', // 显示最后读取的指南针值
                    style: Theme.of(context).textTheme.bodySmall,
                  ),
                  Text(
                    '$_lastReadAt', // 显示最后读取的时间
                    style: Theme.of(context).textTheme.bodySmall,
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildCompass() {
    return StreamBuilder<CompassEvent>(
      stream: FlutterCompass.events,
      builder: (context, snapshot) {
        if (snapshot.hasError) {
          return Text('错误读取方向: ${snapshot.error}');
        }

        if (snapshot.connectionState == ConnectionState.waiting) {
          return Center(
            child: CircularProgressIndicator(), // 加载指示器
          );
        }

        double? direction = snapshot.data!.heading;

        // 如果方向值为null，说明设备不支持该传感器
        // 显示错误信息
        if (direction == null)
          return Center(
            child: Text("设备不具有传感器！"),
          );

        return Material(
          shape: CircleBorder(),
          clipBehavior: Clip.antiAlias,
          elevation: 4.0,
          child: Container(
            padding: EdgeInsets.all(16.0),
            alignment: Alignment.center,
            decoration: BoxDecoration(
              shape: BoxShape.circle,
            ),
            child: Transform.rotate(
              angle: (direction * (math.pi / 180) * -1), // 旋转图像以匹配指南针方向
              child: Image.asset('assets/compass.jpg'), // 指南针图标
            ),
          ),
        );
      },
    );
  }

  Widget _buildPermissionSheet() {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Text('需要位置权限'),
          ElevatedButton(
            child: Text('请求权限'),
            onPressed: () async {
              try {
                var status = await Permission.locationWhenInUse.request();
                print("权限状态: $status");
              } catch (e) {
                print("请求权限错误: $e");
              }

              Permission.locationWhenInUse.request().then((ignored) {
                _fetchPermissionStatus();
              });
            },
          ),
          SizedBox(height: 16),
          ElevatedButton(
            child: Text('打开应用设置'),
            onPressed: () {
              openAppSettings().then((opened) {
                //
              });
            },
          )
        ],
      ),
    );
  }

  void _fetchPermissionStatus() {
    Permission.locationWhenInUse.status.then((status) {
      if (mounted) {
        setState(() => _hasPermissions = status == PermissionStatus.granted);
      }
    });
  }
}