c# - Xamarin Forms 服务与 IsolatedProcess 崩溃

Question

我正在使用 Xamarin Forms 开发一个 Android 应用程序，它由一个界面和一个后台服务组成。我需要该服务在界面应用程序关闭时也能正常工作。如果我将“IsolatedProcess = true”添加到服务中，图形界面仍然有效，但服务崩溃了。我阅读了很多可能的解决方案的帖子，但它们不起作用。 (我尝试在 Release模式下编译并删除“使用共享运行时”标志)。

我正在使用 Android 8.1 (Oreo) 作为目标框架进行编译。目标环境为Android 4.2。

我在 MainActivity 类的 OnCreate 方法中启动服务:

Intent testIntent = new Intent(this.BaseContext, typeof(TestService));
StartService(testIntent);

服务类:

[Service(IsolatedProcess = true, Exported = true, Label = "TestService")]
public class TestService : Service
{

    public override IBinder OnBind(Intent intent)
    {
        return null;
    }

    public override void OnCreate()
    {
        base.OnCreate();

    }

    [return: GeneratedEnum]
    public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
    {            
        Device.StartTimer(new TimeSpan(0, 0, 40), () =>
        {
            //Code executed every 40 seconds
        });

        base.OnStartCommand(intent, flags, startId);
        return StartCommandResult.Sticky;

    }

    public override bool StopService(Intent name)
    {
        return base.StopService(name);
    }

}

如果我删除“IsolatedProcess = true”，该服务会工作，但当我关闭应用程序接口(interface)进程时它会停止。

Answer 1

我通过将属性 IsolatedProcess 的值更改为 true、删除 Device.StartTimer 指令并引入 BroadcastReceiver 解决了这个问题。

MainActivity 类:

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        public static Intent testServiceIntent;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);

            testServiceIntent = new Intent(this.BaseContext, typeof(TestService));

            LoadApplication(new App());
        }
    }

服务类:

[Service(IsolatedProcess = false, Exported = true, Label = "TestService")]
    public class TestService : Service
    {
System.Threading.Timer _timer;

        public override IBinder OnBind(Intent intent)
        {
            return null;
        }

        public override void OnCreate()
        {
            base.OnCreate();
        }

        [return: GeneratedEnum]
        public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
        {
            businessLogicMethod();

            base.OnStartCommand(intent, flags, startId);
            return StartCommandResult.Sticky;

        }

public void businessLogicMethod()
        {
 //My business logic in a System.Threading.Timer

}
}

广播接收器类:

[BroadcastReceiver]
    [IntentFilter(new[] { Intent.ActionBootCompleted })]
    public class TestApplicationBroadcastReceiver : BroadcastReceiver
    {
        public override void OnReceive(Context context, Intent intent)
        {
            Log.Info("TestApp", "******* Loading Application *******");

            try
            {
                if (intent.Action.Equals(Intent.ActionBootCompleted))
                {                    
                    Intent service = new Intent(context, typeof(TestService));
                    service.AddFlags(ActivityFlags.NewTask);
                    context.StartService(service);
                }
            }
            catch (Exception ex)
            {
                Log.Error("TestApp", "******* Error message *******: " + ex.Message);
            }
        }
    }

我希望这对某人有用。