Xamarin - Android - Plugin.InAppBilling 异常

Question

我正在尝试使用插件 InAppBilling为 Xamarin 表单解决方案实现（应用程序内计费）我找不到这个插件的任何完整代码示例或文档，除了这个我一步一步按照说明进行操作，但是当我运行我的代码时，我得到这个例外

{System.NullReferenceException: Current Context/Activity is null，确保 MainApplication.cs 文件在您的源代码中设置 CurrentActivity，以便 In App Billing 可以使用它。在 Plugin.InAppBilling.InAppBillingImplementation.get_Context () [0x00000] 在 C:\projects\inappbillingplugin\src\Plugin.InAppBilling.Android\InAppBillingImplementation.cs:59 在 Plugin.InAppBilling.InAppBillingImplements. itemType) [0x00000] in C:\projects\inappbillingplugin\src\Plugin.InAppBilling.Android\InAppBillingImplementation.cs:372 at myproject.MainPage+d__28.MoveNext () [0x00051] in C:\Users\xuser\source\repos \myproject\MainPage.xaml.cs:415 }

我的示例代码
此代码位于（共享/可移植类库/.NET 标准）

主页.xaml.cs

 public partial class MainPage : ContentPage
    {

     void OnPurchased(object sender, EventArgs e)
            {
              InAppBilling();
            }
     async void InAppBilling()
            {
                try
                {
                    var productId = "xxxxx.xxxx_appbilling";
                    var connected = await CrossInAppBilling.Current.ConnectAsync();
                    if (!connected)
                    {
                        //Couldn't connect to billing, could be offline, alert user
                        return;
                    }
                    //try to purchase item
                    var purchase = await CrossInAppBilling.Current.PurchaseAsync(productId, ItemType.InAppPurchase, "apppayload");
                    if (purchase == null)
                    {
                        //Not purchased, alert the user
                    }
                    else
                    {
                        //Purchased, save this information
                        var id = purchase.Id;
                        var token = purchase.PurchaseToken;
                        var state = purchase.State;
                    }
                }
                catch (Exception ex)
                {
                    //Something bad has occurred, alert user
                }
                finally
                {
                    //Disconnect, it is okay if we never connected
                    await CrossInAppBilling.Current.DisconnectAsync();
                }

            }
}

以及 Droid Project 中的这段代码

 public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
  protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);
            InAppBillingImplementation.HandleActivityResult(requestCode, resultCode, data);
        }
    }

Answer 1

您缺少在OnCreate方法中设置当前活动（上下文）的文档的一部分：

Plugin.CurrentActivity.CrossCurrentActivity.Current.Activity = this;

Android 当前活动设置

该插件使用 Current Activity Plugin 来访问当前的 Android Activity。如果 MainApplication.cs 文件未自动添加到您的应用程序，请务必完成完整设置。请完整阅读当前活动插件文档。您必须至少在 Activity 的 OnCreate 方法中设置以下内容：

• https://jamesmontemagno.github.io/InAppBillingPlugin/GettingStarted.html