UWP App Services in Windows 10

1.AppServices in Universal Windows Platform(UWP)

UWP 应用服务可以提供给另一个UWP应用。在Win10系统中，一个应用服务当作应用的一个方法和机制来提供服务给其他应用。

一个后台任务的应用服务工作的形式（你可以在后台跑代码，通过后台接口实现）。前台客户端可以引用另一个应用的服务在后台中执行任务。

应用服务就像web 服务一样在Win10设备中使用。

首先，让我们来创建一个 Windows Runtime Component (Universal Windows) 项目命名"MyCalculatorService"。这会是我们的计算服务应用。

创建一个以Calculator 为类名的实现 IBackgroundTask接口。在WCF技术中，你可以说这个类是我们的带操作契约的服务契约

    public sealed class Calculator : IBackgroundTask
    {
        private BackgroundTaskDeferral backgroundTaskDeferral;
        private AppServiceConnection appServiceConnection;
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            this.backgroundTaskDeferral = taskInstance.GetDeferral();

            var details = taskInstance.TriggerDetails as AppServiceTriggerDetails;
            appServiceConnection = details.AppServiceConnection;

            appServiceConnection.RequestReceived += OnRequestReceived;
            taskInstance.Canceled += OnTaskCanceled;
        }

        private async void OnRequestReceived(AppServiceConnection sender, AppServiceRequestReceivedEventArgs args)
        {
            var messageDeferral = args.GetDeferral();
            ValueSet message = args.Request.Message;
            ValueSet returnData = new ValueSet();

            string command = message["Command"] as string;      //Add, Subtract, Multiply, Divide
            int? firstNumber = message["Input1"] as int?;
            int? secondNumber = message["Input2"] as int?;
            int? result = 0;

            if (firstNumber.HasValue && secondNumber.HasValue)
            {
                switch (command)
                {
                    case "Add":
                        {
                            result = firstNumber + secondNumber;
                            returnData.Add("Result", result.ToString());
                            returnData.Add("Status", "Complete");
                            break;
                        }
                    case "Subtract":
                        {
                            result = firstNumber - secondNumber;
                            returnData.Add("Result", result.ToString());
                            returnData.Add("Status", "Complete");
                            break;
                        }
                    case "Multiply":
                        {
                            result = firstNumber * secondNumber;
                            returnData.Add("Result", result.ToString());
                            returnData.Add("Status", "Complete");
                            break;
                        }
                    case "Divide":
                        {
                            result = firstNumber / secondNumber;
                            returnData.Add("Result", result.ToString());
                            returnData.Add("Status", "Complete");
                            break;
                        }
                    default:
                        {
                            returnData.Add("Status", "Fail: unknown command");
                            break;
                        }
                }
            }

            await args.Request.SendResponseAsync(returnData);
            messageDeferral.Complete();
        }

        private void OnTaskCanceled(IBackgroundTaskInstance sender, BackgroundTaskCancellationReason reason)
        {
            if (this.backgroundTaskDeferral != null)
            {
                this.backgroundTaskDeferral.Complete();
            }
        }
    }

View Code

现在下一步来创建一个项目来暴露这个功能在客户端应用（类似WCF环境的宿主）

创建UWP项目命名MyCalculatorServiceProvider。导入 MyCalculatorService 项目从引用里。

现在打开MyCalculatorServiceProvider 项目的Package.appxmanifest文件。右键打开，找到申明应用服务实例命名CalculatorService1 ，

在entry point 中键入MyCalculatorService.Calculator （看上面的代码，这是实现IBackgroundTask的类）

最后一步来运行创建的这个服务客户端，这个服务提供的应用必须要部署在你调用服务之前。你也需要这个服务应用（MyCalculatorServiceProvider ）的包名，为了调用他。

在创建一个UWP项目命名 CalculatorClient。你会注意到这个名字是以服务名定义的，为了得到PackageFamilyName 我们有两种方法。

第一个方法：通过调用 Windows.ApplicationModel.Package.Current.Id.FamilyName 包含在 MyCalculatorServiceProvider 项目中可以跑一下。

第二个方法：找到部署MyCalculatorServiceProvider 项目的全路径

图片选中的 d1238b67-b1ef-4782-9f3e-df718d97e378_8wekyb3d8bbwe 这个就是 PackageFamilyName

这是核心代码

public sealed partial class MainPage : Page
    {
    private AppServiceConnection calculatorService;

    public MainPage()
        {
            this.InitializeComponent();
        }

    private async void button_Click(object sender, RoutedEventArgs e)
    {
        //Add the connection
        if (calculatorService == null)
        {
            calculatorService = new AppServiceConnection();
            calculatorService.AppServiceName = "CalculatorService1";
            calculatorService.PackageFamilyName = "83da5395-2473-49fb-b361-37072e87e9b9_xe3s0d4n4696a";

            var status = await calculatorService.OpenAsync();

            if (status != AppServiceConnectionStatus.Success)
            {
                Result.Content = "Failed to connect";
                return;
            }
        }

        //Call the service
        int num1 = int.Parse(InputtextBox1.Text);
        int num2 = int.Parse(InputtextBox2.Text);
        var message = new ValueSet();

        message.Add("Command", Operation.SelectionBoxItem);
        message.Add("Input1", num1);
        message.Add("Input2", num2);

        AppServiceResponse response = await calculatorService.SendMessageAsync(message);
        string result = "";

        if (response.Status == AppServiceResponseStatus.Success)
        {
            //Get the data that the service sent
            if (response.Message["Status"] as string == "Complete")
            {
                result = response.Message["Result"] as string;
            }
        }
        message.Clear();
        ResulttextBlock.Text = result;
    }
    }