MAUI 依赖服务获取返回 null

Question

我正在尝试在我的 MAUI 应用程序中使用手机上的蓝牙。我关注了这篇文章。 我知道这可能不是最好的资源，但我找不到其他资源。 我是否在某个地方犯了错误，或者这不是正确的策略？

对于上下文，我正在尝试通过 HC-05 模块连接到我的 arduino。

但是，当我尝试使用 DependencyService.Get 时，它返回 null。

这是我的界面，位于 App.xaml.cs 中：

namespace RobotControl
{

    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();

            MainPage = new AppShell();

        }
    }

    


    public interface IBluetoothConnector
    {
        List<string> GetConnectedDevices();
        void Connect(string deviceName);

        public void Write(byte[] data);
    }
}

这是我的实现，位于 Platforms/Android/BluetoothConnector.cs:

using Android.Bluetooth;
using Java.Util;
using RobotControl.Platforms.Android.Bluetooth;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
[assembly: Dependency(typeof(RobotControl.Platforms.Android.Bluetooth.BluetoothConnector))]
namespace RobotControl.Platforms.Android.Bluetooth
{
    class BluetoothConnector : IBluetoothConnector
    {

        BluetoothAdapter adapter;
        private const string SspUuid = "00001101-0000-1000-8000-00805f9b34fb";
        private BluetoothSocket? socket;
        public void Connect(string deviceName)
        {
            var device = adapter.BondedDevices.FirstOrDefault(d=> d.Name == deviceName);
            socket = device.CreateRfcommSocketToServiceRecord(UUID.FromString(SspUuid));
            socket.Connect();
        
        }

        public void Write(byte[] data) 
        { 
        
        }


        public List<string> GetConnectedDevices()
        {
            adapter = BluetoothAdapter.DefaultAdapter;
            if (adapter == null) 
            {
                throw new Exception("No Bluetooth adapter");
            }

            if (adapter.IsEnabled)
            { 
                if(adapter.BondedDevices.Count >0)
                {
                    return adapter.BondedDevices.Select(x => x.Name).ToList();
                }
            
            }
            else
            {
                Console.WriteLine("BT is not enabled");
            }

            return new List<string>();
                
        }
    }



}
namespace RobotControl
{

    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();

            MainPage = new AppShell();

        }
    }

    


    public interface IBluetoothConnector
    {
        List<string> GetConnectedDevices();
        void Connect(string deviceName);

        public void Write(byte[] data);
    }
}

我正在尝试访问该服务。 Lhand.xaml.cs

namespace RobotControl
{

    public partial class LHand : ContentPage
    {
        public int L_PinkyAngle;
        public int L_RingAngle;
        public int L_MiddleAngle;
        public int L_IndexAngle;
        public int L_ThumbAngle;
        public int L_RotaAngle;




        public LHand()
        {
            InitializeComponent();


        }

        private async void SPinky_ValueChanged(object sender, ValueChangedEventArgs e)
        {

            var connector = DependencyService.Get<IBluetoothConnector>();
            
            if(connector == null)
            {
                await DisplayAlert("er", "connector is null", "huh");
            }
            else
            {
                await DisplayAlert("er", "isnt null", "huh");
            }

            string x = "";
            foreach(string s in connector.GetConnectedDevices())
            {
                x += s + "\n";
            }

            await DisplayAlert("er", x+ "", "huh");



        }

        private void SRing_ValueChanged(object sender, ValueChangedEventArgs e)
        {

        }

        private void SMiddle_ValueChanged(object sender, ValueChangedEventArgs e)
        {

        }

        private void SIndex_ValueChanged(object sender, ValueChangedEventArgs e)
        {

        }

        private void SThumb_ValueChanged(object sender, ValueChangedEventArgs e)
        {

        }
    }
}

感谢您的帮助。

Answer 1

您注册了该服务吗？

// App.xaml.cs
DependencyService.Register<IBluetoothConnector, BluetoothConnector>();

另外，请参阅这个问题MAUI：DependencyService.Get（）返回null