Question

当我使用SocketActivityTrigger时，为什么需要检查pushNotifications功能？它的目的是什么？

Answer 1

You don't.

Push notification capability (ID_CAP_PUSH_NOTIFICATION) is for Windows Phone 8/8.1 Silverlight.

Both Windows Runtime 8.1 and UWP (Windows 10) do not have a push notifications capability, see the list of all capabilities in UWP.

If you check the official sample for SocketActivityTrigger, you'll see it only uses capabilities for internet connectivity.

<Capabilities>
    <Capability Name="internetClient" />
    <Capability Name="privateNetworkClientServer" />
</Capabilities>