我收到一個(gè)錯(cuò)誤,我無(wú)法理解：

我在void方法中有這個(gè)簡(jiǎn)單的警告對(duì)話框構(gòu)建器

private void startAction() {
                AlertDialog.Builder builder;
                builder = new AlertDialog.Builder (this);
                var ad = builder.Create ();
                builder.SetMessage ("Some text");
                builder.SetPositiveButton ("OK", delegate { 
                    ad.Dismiss ();
                    ShowDialog (0);
                });
                builder.SetNegativeButton ("Cancel", delegate { 
                    ad.Cancel ();
                });
                builder.SetCancelable (true);                    
                builder.Show ();
}

Xamarin Insights向我展示了一份我不能復(fù)制或理解的崩潰報(bào)告(多次).

System.ArgumentException'jobject' must not be IntPtr.Zero. Parameter name: jobject
Raw
Android.Runtime.JNIEnv.CallVoidMethod(IntPtr jobject, IntPtr jmethod)
Android.App.Dialog.Dismiss()
SpoonacularApp.Droid.ShoppingListActivity.<startAction>c__AnonStorey3.<>m__0(object, DialogClickEventArgs)
Android.Content.IDialogInterfaceOnClickListenerImplementor.OnClick(IDialogInterface dialog, int which)
Android.Content.IDialogInterfaceOnClickListenerInvoker.n_OnClick_Landroid_content_DialogInterface_I(IntPtr jnienv, IntPtr native__this, IntPtr native_dialog, int which)
at (wrapper dynamic-method) System.Object:ba5962df-899a-46fd-a4bd-6c9ffe426b75 (intptr,intptr,intptr,int)

這個(gè)例外談?wù)摰氖悄膫€(gè)論點(diǎn)？

我得到了與Android.App.Dialog.Cancel()而不是Android.App.Dialog.Dismiss()相同的錯(cuò)誤消息.

解決方法:

AlertDialog廣告的peer connection;已被切斷;雖然該對(duì)象仍然可以在.NET中使用(通過(guò)點(diǎn)擊處理程序),但它已經(jīng)收集了Java對(duì)應(yīng)物.這兩個(gè)對(duì)象之間的綁定保存在存儲(chǔ)在IntPtr Handle屬性中的全局引用中,用于實(shí)現(xiàn)IJavaObject的.NET中的所有對(duì)象.

當(dāng)發(fā)生跨VM收集周期時(shí),Handle設(shè)置為IntPtr.Zero并釋放全局Java引用以使Dalvik(Java)能夠收集Java對(duì)象.

您看到此次崩潰是因?yàn)樵搼?yīng)用可能已經(jīng)落后,并且Android已觸發(fā)了應(yīng)用流程的集合.這導(dǎo)致大多數(shù)Java資源被Dalviks垃圾收集器破壞,但它們相應(yīng)的.NET對(duì)象仍處于活動(dòng)狀態(tài),現(xiàn)在指向無(wú)效的Java對(duì)象.

解決此問(wèn)題的方法是使用following code snippet檢查AlertDialog的單擊處理程序內(nèi)的對(duì)等連接：

public static class PeerConnectionHelper
{
    public static bool HasPeerConnection(Java.Lang.Object jObj)
    {
        return !(jObj == null || jObj.Handle == System.IntPtr.Zero);
    }

    public static bool HasPeerConnection (Android.Runtime.IJavaObject jObj)
    {
        return !(jObj == null || jObj.Handle == System.IntPtr.Zero);
    }
}

這將實(shí)現(xiàn)如下：

builder.SetPositiveButton ("OK", delegate { 
    if (!PeerConnectionHelper.HasPeerConnection(ad)) {
        return;
    }

    ad.Dismiss ();
    ShowDialog (0);
});
builder.SetNegativeButton ("Cancel", delegate { 
    if (!PeerConnectionHelper.HasPeerConnection(ad)) {
        return;
    }

    ad.Cancel ();
});