在过去的3天里，我一直在尝试远程创建和使用Windows 10 UWP AppService。当AppService在一台笔记本电脑上运行而客户端在另一台笔记本电脑（桌面到桌面）上运行时，我就完成了所有工作。但是，当我在手机上安装客户端时，IBackgroundTaskInstance取消原因：SystemPolicy。我不知道为什么在手机到桌面的情况下它不起作用。任何人都知道从哪里开始寻找？
以下是我的服务类
using Newtonsoft.Json;
using SharedObjects;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
using Windows.ApplicationModel;
using Windows.ApplicationModel.AppService;
using Windows.ApplicationModel.Background;
using Windows.ApplicationModel.Core;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.Management.Deployment;
using Windows.Storage.Streams;
namespace AppStarterService
{
public sealed class AppStarterTask : IBackgroundTask
{
BackgroundTaskDeferral serviceDeferral;
AppServiceConnection connection;
public void Run(IBackgroundTaskInstance taskInstance)
{
try
{
serviceDeferral = taskInstance.GetDeferral();
taskInstance.Canceled += OnTaskCanceled;
var details = taskInstance.TriggerDetails as AppServiceTriggerDetails;
if (details.Name == "com.poctools.appstarter")
{
connection = details.AppServiceConnection;
connection.RequestReceived += OnRequestReceived;
connection.ServiceClosed += Connection_ServiceClosed;
}
else
{
serviceDeferral.Complete();
}
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
throw;
}
}
async void OnRequestReceived(AppServiceConnection sender, AppServiceRequestReceivedEventArgs args)
{
var messageDeferral = args.GetDeferral();
try
{
var input = args.Request.Message;
var packageList = await GetPackageListInfo();
var json = JsonConvert.SerializeObject(packageList, Formatting.None);
var result = new ValueSet();
result.Add("result", json);
Debug.WriteLine(json);
var response = await args.Request.SendResponseAsync(result); //returns Success, even on the phone-to-desktop scenario
Debug.WriteLine($"Send result: {response}");
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
finally
{
messageDeferral.Complete();
}
}
private void Connection_ServiceClosed(AppServiceConnection sender, AppServiceClosedEventArgs args)
{
Debug.WriteLine($"Service closed: {args.Status}");
}
private void OnTaskCanceled(IBackgroundTaskInstance sender, BackgroundTaskCancellationReason reason)
{
Debug.WriteLine($"Task cancelled: {reason}");
if (serviceDeferral != null)
{
serviceDeferral.Complete();
serviceDeferral = null;
}
if (connection != null)
{
connection.Dispose();
connection = null;
}
}
private async Task<List<PackageInfo>> GetPackageListInfo()
{
try
{
List<PackageInfo> PackageInfoList = new List<PackageInfo>();
PackageManager packageManager = new PackageManager();
var Packages = packageManager.FindPackagesForUser("");
foreach (var package in Packages.Where(p => p.SignatureKind == PackageSignatureKind.Store && !p.IsFramework))
{
IReadOnlyList<AppListEntry> entryList = await package.GetAppListEntriesAsync();
if (entryList != null)
{
foreach (var entry in entryList)
{
if (entry != null)
{
Debug.WriteLine(entry.DisplayInfo.DisplayName);
var name = entry.DisplayInfo.DisplayName;
RandomAccessStreamReference stream = entry.DisplayInfo.GetLogo(new Size(150, 150));
if (stream != null)
{
var streamContent = await stream.OpenReadAsync();
if (streamContent != null)
{
byte[] buffer = new byte[streamContent.Size];
await streamContent.ReadAsync(buffer.AsBuffer(), (uint)streamContent.Size, InputStreamOptions.None);
string logo = Convert.ToBase64String(buffer);
PackageInfoList.Add(new PackageInfo(name, package.Id.FamilyName, logo));
}
}
}
}
}
Debug.WriteLine($"{package.Id.Name} - {package.SignatureKind}");
}
return PackageInfoList;
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
throw;
}
}
}
}
可以在主机和客户端之间发送数据包大小的限制，显然我的手机只有几KB。 GetPackageListInfo（）方法获取主机上所有已安装应用程序的列表，其中包含名称和徽标。一些应用程序有大徽标（Minecraft有一个9 KB的徽标，它很大，Paint 3D的徽标是27 KB）。最后我让服务一次返回1个PackageInfo，让客户端调用服务直到服务返回最后一个PackageInfo，并减少任何大于8KB的徽标。
https://docs.microsoft.com/en-us/windows/uwp/launch-resume/how-to-create-and-consume-an-app-service的另一个兴趣点
应用服务的生命周期取决于呼叫者：
码：
async void OnRequestReceived(AppServiceConnection sender, AppServiceRequestReceivedEventArgs args)
{
var messageDeferral = args.GetDeferral();
try
{
var inputs = args.Request.Message;
if (Singleton.Instance.PackageList == null)
Singleton.Instance.PackageList = await GetPackageListInfo();
var itemsSend = inputs["items"] as string[]; //keep track of items already send
inputs["items"] = null; //clear to keep response data small (it will be filled again when a new request comes in)
var package = Singleton.Instance.PackageList.FirstOrDefault(p => !itemsSend.Contains(p.Id));
if (package == null)
{
inputs["status"] = "stop"; //let the client know it's time to stop requesting
inputs["package"] = null;
}
else
{
var json = JsonConvert.SerializeObject(package);
inputs["package"] = json;
}
var response = await args.Request.SendResponseAsync(inputs);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
finally
{
messageDeferral?.Complete();
}
}
ResizeImage
async Task<byte[]> ResizeImage(byte[] imageData, int reqWidth, int reqHeight)
{
var memStream = new MemoryStream(imageData);
using (IRandomAccessStream imageStream = memStream.AsRandomAccessStream())
{
//Get BitmapDecoder based on the original image
var decoder = await BitmapDecoder.CreateAsync(imageStream);
if (decoder.PixelHeight > reqHeight || decoder.PixelWidth > reqWidth)
{
//BitmapTransform defines a set of transformation to be applied to the original image (we're just interessted in scaling down)
BitmapTransform transform = new BitmapTransform()
{
ScaledHeight = (uint)reqHeight,
ScaledWidth = (uint)reqWidth,
InterpolationMode = BitmapInterpolationMode.Linear
};
PixelDataProvider pixelData = await decoder.GetPixelDataAsync(
BitmapPixelFormat.Rgba8,
BitmapAlphaMode.Straight,
transform,
ExifOrientationMode.IgnoreExifOrientation,
ColorManagementMode.ColorManageToSRgb);
var resizedStream = new InMemoryRandomAccessStream();
BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, resizedStream);
var pixels = pixelData.DetachPixelData();
encoder.SetPixelData(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Straight, (uint)reqWidth, (uint)reqHeight, 96, 96, pixels);
await encoder.FlushAsync();
var outBuffer = new byte[resizedStream.Size];
await resizedStream.ReadAsync(outBuffer.AsBuffer(), (uint)resizedStream.Size, InputStreamOptions.None);
return outBuffer;
}
}
return imageData;
}
GetPackageListInfo
private async Task<List<PackageInfo>> GetPackageListInfo()
{
try
{
List<PackageInfo> PackageInfoList = new List<PackageInfo>();
PackageManager packageManager = new PackageManager();
IEnumerable<Package> Packages = packageManager.FindPackagesForUser("");
foreach (var package in Packages.Where(p => p.SignatureKind == PackageSignatureKind.Store && !p.IsFramework))
{
IReadOnlyList<AppListEntry> entryList = await package.GetAppListEntriesAsync();
if (entryList != null)
{
foreach (var entry in entryList)
{
if (entry != null)
{
var name = entry.DisplayInfo.DisplayName;
RandomAccessStreamReference stream = entry.DisplayInfo.GetLogo(new Size(50, 50));
if (stream != null)
{
var streamContent = await stream.OpenReadAsync();
if (streamContent != null)
{
byte[] buffer = new byte[streamContent.Size];
await streamContent.ReadAsync(buffer.AsBuffer(), (uint)streamContent.Size, InputStreamOptions.None);
if (streamContent.Size < 9000)
{
PackageInfoList.Add(new PackageInfo(package.Id.FullName, name, package.Id.FamilyName, buffer));
}
else
{
byte[] resizedBuffer = await ResizeImage(buffer, 50, 50);
if (resizedBuffer.Length < 8192)//8kb
PackageInfoList.Add(new PackageInfo(package.Id.FullName, name, package.Id.FamilyName, resizedBuffer));
}
}
}
}
}
}
//Debug.WriteLine($"{package.Id.Name} - {package.SignatureKind}");
}
return PackageInfoList;
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
throw;
}
}