C# 如何在Android中从多个活动调用同一服务实例

我刚刚开始研究Xamarin，只是不知道如何使多个活动具有同一服务实例的引用

我正在从

main活动启动
按键接收程序
，并开始监听电源按钮是否被按下

当进行三次单击时，我调用服务方法
InitCancelActivity
，它开始播放mp3文件并打开
CancelActivity

在
CancelActivity
中有一个文本字段和一个按钮。当用户按下此按钮时，我希望文本字段中的值传递到
GeneralService
方法
KillAlert

问题是如何从
CancelActivity
引用
GeneralService
（已创建）的实例，以便调用
KillAlert

这部分呢

if (_service == null)
    _service = new GeneralService();

看起来完全错了。我应该在
main活动中实例化它
并传递给
KeyPressedReceiver
构造函数吗

[Activity(Label = "TTTT", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    KeyPressedReceiver receiver;
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Main);

        receiver = new KeyPressedReceiver();
        RegisterReceiver(receiver, new IntentFilter(Intent.ActionScreenOn));
    }
}


[BroadcastReceiver(Enabled = true)]
public class KeyPressedReceiver : BroadcastReceiver
{
    private GeneralService _service;
    private int _clicks = 0;
    public override void OnReceive(Context context, Intent intent)
    {
         if (_service == null)
            _service = new GeneralService();

        _clicks++;

        if (_clicks > 5)
        {
            _service.InitCancelActivity();
        }
    }
}


[Service(Name = "com.ff.GeneralService")]
public class GeneralService : Service {
    private readonly Android.Media.MediaPlayer _player;

    public GeneralService()
    {
        _player = new Android.Media.MediaPlayer(); 
    }

    public void RaiseAlert()
    {
        // start playing .mp3 file
    }

    public void KillAlert(string pass)
    {
        // stop playing .mp3 file
    }

    public void InitCancelActivity()
    {
        this.RaiseAlert();

        var i = new Intent(this, typeof(CancelActivity));
        i.SetFlags(ActivityFlags.NewTask);
        this.StartActivity(i);
    }
}

[Activity(Label = "CancelActivity")]
public class CancelActivity : Activity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.cancel);

        this.FindViewById(Resource.Id.cancelButtonYes).Click += delegate
        {
            var password = this.FindViewById(Resource.Id.cancelPassword);

            // call KillAlert method from GeneralServic
        };
    }
}

创建静态GeneralService实例并在取消活动中使用。
比如说

[Service(Name = "com.ff.GeneralService")]
public class GeneralService : Service {
    private readonly Android.Media.MediaPlayer _player;
    public static generalService;
    public GeneralService()
    {
        _player = new Android.Media.MediaPlayer(); 
         generalService=this
    }

    public void RaiseAlert()
    {
        // start playing .mp3 file
    }

    public void KillAlert(string pass)
    {
        // stop playing .mp3 file
    }

    public void InitCancelActivity()
    {
        this.RaiseAlert();

        var i = new Intent(this, typeof(CancelActivity));
        i.SetFlags(ActivityFlags.NewTask);
        this.StartActivity(i);
    }
}

并在取消活动中使用，如下面的示例所示

[Activity(Label = "CancelActivity")]
public class CancelActivity : Activity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.cancel);

        this.FindViewById(Resource.Id.cancelButtonYes).Click += delegate
        {
            var password = this.FindViewById(Resource.Id.cancelPassword);

            // call KillAlert method from GeneralServic
          GeneralService.generalService.KillAlert(password.TEXT);

        };
    }
}

创建静态GeneralService实例并在取消活动中使用。
比如说

[Service(Name = "com.ff.GeneralService")]
public class GeneralService : Service {
    private readonly Android.Media.MediaPlayer _player;
    public static generalService;
    public GeneralService()
    {
        _player = new Android.Media.MediaPlayer(); 
         generalService=this
    }

    public void RaiseAlert()
    {
        // start playing .mp3 file
    }

    public void KillAlert(string pass)
    {
        // stop playing .mp3 file
    }

    public void InitCancelActivity()
    {
        this.RaiseAlert();

        var i = new Intent(this, typeof(CancelActivity));
        i.SetFlags(ActivityFlags.NewTask);
        this.StartActivity(i);
    }
}

并在取消活动中使用，如下面的示例所示

[Activity(Label = "CancelActivity")]
public class CancelActivity : Activity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.cancel);

        this.FindViewById(Resource.Id.cancelButtonYes).Click += delegate
        {
            var password = this.FindViewById(Resource.Id.cancelPassword);

            // call KillAlert method from GeneralServic
          GeneralService.generalService.KillAlert(password.TEXT);

        };
    }
}

这就是我现在所拥有的，但出于某种原因，这似乎是错误的。但也许这就是我现在拥有的，但出于某种原因，它似乎是错的。但也许只有我一个人