CurrieTechnologies.Blazor.PageVisibility 0.2.2

CurrieTechnologies.Blazor.PageVisibility

This package provides Blazor applications with access to the browser's Page Visibility API

Usage

1. In your Blazor app, add the CurrieTechnologies.Blazor.PageVisibility NuGet package

   Install-Package CurrieTechnologies.Blazor.PageVisibility
   

2. In your Blazor app's Startup.cs, register the 'PageVisibilityService'.

   public void ConfigureServices(IServiceCollection services)
   {
       ...
       services.AddPageVisibility();
       ...
   }
   

3. Now you can inject the PageVisibilityService into any Blazor page and use it like this:

   @inject PageVisibilityService visibility
   
   <div>
     <ul>
       @foreach (var vs in viewStates)
       {
         <li>@vs</li>
       }
     </ul>
     @if (listenerId != Guid.Empty)
     {
       <button onclick="@HandleUnsubscibe">Unsubscribe</button>
     }
     else
     {
       <button onclick="@(async () => listenerId = await visibility.OnVisibilityChangeAsync(OnVisibilityChange, this))">
         Resubscribe
       </button>
     }
   
   </div>
   
   @functions {
     private List<string> viewStates = new List<string>();
     private Guid listenerId = Guid.Empty;
   
     protected override async Task OnInitAsync()
     {
       viewStates.Add(await visibility.GetVisibilityStateAsync());
   
       listenerId = await visibility.OnVisibilityChangeAsync(OnVisibilityChange, this);
   
       await base.OnInitAsync();
     }
   
     Task OnVisibilityChange(VisibilityInfo visibilityInfo)
     {
       viewStates.Add(visibilityInfo.VisibilityState);
       return Task.CompletedTask;
     }
   
     async Task HandleUnsubscibe()
     {
       await visibility.RemoveVisibilityChangeCallbackAsync(listenerId);
       listenerId = Guid.Empty;
     }
   }