System.InvalidOperationException Android

Question

在Xamarin上编写Android应用。

有这个错误

 [MonoDroid] UNHANDLED EXCEPTION: [MonoDroid] System.InvalidOperationException: Operation is not valid due to the current state of the object [MonoDroid] at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x00028> [MonoDroid] at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (object) <0x0003f> [MonoDroid] at Android.App.SyncContext/<Post>c__AnonStorey0.<>m__0 () <0x00027> [MonoDroid] at Java.Lang.Thread/RunnableImplementor.Run () <0x0003f> [MonoDroid] at Java.Lang.IRunnableInvoker.n_Run (intptr,intptr) <0x0003b> [MonoDroid] at (wrapper dynamic-method) object.abf695dd-f4ec-4a71-8e1c-73614b06354b (intptr,intptr) <0x0003b> [AndroidRuntime] Shutting down VM [AndroidRuntime] FATAL EXCEPTION: main [AndroidRuntime] java.lang.RuntimeException: java.lang.reflect.InvocationTargetException [AndroidRuntime] at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608) [AndroidRuntime] at dalvik.system.NativeStart.main(Native Method) [AndroidRuntime] Caused by: java.lang.reflect.InvocationTargetException [AndroidRuntime] at java.lang.reflect.Method.invokeNative(Native Method) [AndroidRuntime] at java.lang.reflect.Method.invoke(Method.java:511) [AndroidRuntime] at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841) [AndroidRuntime] ... 2 more [AndroidRuntime] Caused by: md52ce486a14f4bcd95899665e9d932190b.JavaProxyThrowable: System.InvalidOperationException: Operation is not valid due to the current state of the object [AndroidRuntime] at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x00028> [AndroidRuntime] at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (object) <0x0003f> [AndroidRuntime] at Android.App.SyncContext/<Post>c__AnonStorey0.<>m__0 () <0x00027> [AndroidRuntime] at Java.Lang.Thread/RunnableImplementor.Run () <0x0003f> [AndroidRuntime] at Java.Lang.IRunnableInvoker.n_Run (intptr,intptr) <0x0003b> [AndroidRuntime] at (wrapper dynamic-method) object.abf695dd-f4ec-4a71-8e1c-73614b06354b (intptr,intptr) <0x0003b> [AndroidRuntime] [AndroidRuntime] at mono.java.lang.RunnableImplementor.n_run(Native Method) [AndroidRuntime] at mono.java.lang.RunnableImplementor.run(RunnableImplementor.java:29) [AndroidRuntime] at android.os.Handler.handleCallback(Handler.java:725) [AndroidRuntime] at android.os.Handler.dispatchMessage(Handler.java:92) [AndroidRuntime] at android.os.Looper.loop(Looper.java:153) [AndroidRuntime] at android.app.ActivityThread.main(ActivityThread.java:5330) 

我通过网址做解析器

解析器代码

string url2 = "http://new.murakami.ua/?mkapi=getProductsByCat&cat_id=182";
    JsonValue json = await FetchAsync(url2);

    ParseAndDisplay1(json);
    ParseAndDisplay2(json);
    ParseAndDisplay3(json);
private async Task<JsonValue> FetchAsync(string url2)
{
    // Create an HTTP web request using the URL:
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url2));
    request.ContentType = "application/json";
    request.Method = "GET";`

    // Send the request to the server and wait for the response:
    using (WebResponse response = await request.GetResponseAsync())
    {
        // Get a stream representation of the HTTP web response:
        using (Stream stream = response.GetResponseStream())
        {
            // Use this stream to build a JSON document object:
            JsonValue jsonDoc = await Task.Run(() => JsonObject.Load(stream));

            Console.Out.WriteLine("Response: {0}", jsonDoc.ToString());


            // Return the JSON document:
            return jsonDoc;
        }
    }
}

private void ParseAndDisplay1(JsonValue json)
{


    //ImageButton product = FindViewById<ImageButton>(Resource.Id.vugor);
    TextView productname = FindViewById<TextView>(Resource.Id.posttittle);
    TextView price = FindViewById<TextView>(Resource.Id.price);
    TextView weight = FindViewById<TextView>(Resource.Id.weight);
    JsonValue firstitem = json[43];
    //Console.Out.WriteLine(firstitem["post_title"].ToString());
    productname.Text = firstitem["post_title"];
    price.Text = firstitem["price"] + " грн";
    weight.Text = firstitem["weight"] + "г";
    productname.Click += delegate
    {
        var intent485 = new Intent(this, typeof(LanchiDetails1));
        StartActivity(intent485);
    };



}
private void ParseAndDisplay2(JsonValue json)
{


    //ImageButton product = FindViewById<ImageButton>(Resource.Id.vugor);
    TextView productname = FindViewById<TextView>(Resource.Id.posttittle1);
    TextView price = FindViewById<TextView>(Resource.Id.price1);
    TextView weight = FindViewById<TextView>(Resource.Id.weight1);
    JsonValue firstitem = json[3];
    //Console.Out.WriteLine(firstitem["post_title"].ToString());
    productname.Text = firstitem["post_title"];
    price.Text = firstitem["price"] + " грн";
    weight.Text = firstitem["weight"] + "г";

    productname.Click += delegate
    {
        var intent486 = new Intent(this, typeof(LanchiDetails2));
        StartActivity(intent486);
    };



}
private void ParseAndDisplay3(JsonValue json)
{


    //ImageButton product = FindViewById<ImageButton>(Resource.Id.vugor);
    TextView productname = FindViewById<TextView>(Resource.Id.posttittle2);
    TextView price = FindViewById<TextView>(Resource.Id.price2);
    TextView weight = FindViewById<TextView>(Resource.Id.weight2);
    JsonValue firstitem = json[2];
    //Console.Out.WriteLine(firstitem["post_title"].ToString());
    productname.Text = firstitem["post_title"];
    price.Text = firstitem["price"] + " грн";
    weight.Text = firstitem["weight"] + "г";
    productname.Click += delegate
    {
        var intent487 = new Intent(this, typeof(LanchiDetails3));
        StartActivity(intent487);
    };


}

我尝试评论ParseAndDisplay- ParseAndDisplay3

并查看响应

但是，当我取消注释ParseAndDisplay -ParseAndDisplay3时，出现错误“应用程序已停止”。

代码有什么问题？

Answer 1

您的异步任务（FetchAsync）仍在运行时，似乎正在调用您对ParseAndDisplay的调用。

在您的ParseAndDisplay函数中，检查json的值，您可能会发现它为null。

您需要等待FetchAsync完成才能调用ParseAndDisplay。 或者您可以从FetchAsync调用ParseAndDisplay

Answer 2

解决方案是这样的：

旧API

 Array ( [43] => WP_Post Object ( [ID] => 4378 [post_author] => 4 [post_date] => 2015-10-01 12:47:54 [post_date_gmt] => 2015-10-01 08:47:54 [post_content] => [post_title] => Ямато [post_excerpt] => Курячий бульйон з яйцем / салат овочевий з заправкою насу / крохмальна локшина з овочами та свининою [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => yamato-0 [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:38:18 [post_modified_gmt] => 2015-10-08 10:38:18 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/yamato-0/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/YAmato.jpg [visibility] => visible [price] => 99.00 [weight] => 225/110/175 [energy] => [sku] => 172 [category] => 182 ) [3] => WP_Post Object ( [ID] => 4377 [post_author] => 4 [post_date] => 2015-10-01 12:47:54 [post_date_gmt] => 2015-10-01 08:47:54 [post_content] => [post_title] => Хонсю [post_excerpt] => Місо суп / салат овочевий з лососем / курячі крильця теріякі з сирним соусом [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => honsyu [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:37:27 [post_modified_gmt] => 2015-10-08 10:37:27 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/honsyu/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/Honsyu.jpg [visibility] => visible [price] => 99.00 [weight] => 165/120/180/40 [energy] => [sku] => 156 [category] => 182 ) [4] => WP_Post Object ( [ID] => 4237 [post_author] => 7 [post_date] => 2015-09-08 12:29:11 [post_date_gmt] => 2015-09-08 08:29:11 [post_content] => [post_title] => Фудзіяма [post_excerpt] => Суп суймоно з кальмаром / салат теріякі з куркою / рол з огірком / рис смажений з грибами [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => fudziyama [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:38:51 [post_modified_gmt] => 2015-10-08 10:38:51 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/fudziyama/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/Fudziyama.jpg [visibility] => visible [price] => 99.00 [weight] => 210/140/116/180 [energy] => [sku] => 471 [category] => 182 ) ) 

新API

 Array ( [0] => WP_Post Object ( [ID] => 4378 [post_author] => 4 [post_date] => 2015-10-01 12:47:54 [post_date_gmt] => 2015-10-01 08:47:54 [post_content] => [post_title] => Ямато [post_excerpt] => Курячий бульйон з яйцем / салат овочевий з заправкою насу / крохмальна локшина з овочами та свининою [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => yamato-0 [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:38:18 [post_modified_gmt] => 2015-10-08 10:38:18 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/yamato-0/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/YAmato.jpg [visibility] => visible [price] => 99.00 [weight] => 225/110/175 [energy] => [sku] => 172 [category] => 182 ) [1] => WP_Post Object ( [ID] => 4377 [post_author] => 4 [post_date] => 2015-10-01 12:47:54 [post_date_gmt] => 2015-10-01 08:47:54 [post_content] => [post_title] => Хонсю [post_excerpt] => Місо суп / салат овочевий з лососем / курячі крильця теріякі з сирним соусом [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => honsyu [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:37:27 [post_modified_gmt] => 2015-10-08 10:37:27 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/honsyu/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/Honsyu.jpg [visibility] => visible [price] => 99.00 [weight] => 165/120/180/40 [energy] => [sku] => 156 [category] => 182 ) [2] => WP_Post Object ( [ID] => 4237 [post_author] => 7 [post_date] => 2015-09-08 12:29:11 [post_date_gmt] => 2015-09-08 08:29:11 [post_content] => [post_title] => Фудзіяма [post_excerpt] => Суп суймоно з кальмаром / салат теріякі з куркою / рол з огірком / рис смажений з грибами [post_status] => publish [comment_status] => open [ping_status] => closed [post_password] => [post_name] => fudziyama [to_ping] => [pinged] => [post_modified] => 2015-10-08 14:38:51 [post_modified_gmt] => 2015-10-08 10:38:51 [post_content_filtered] => [post_parent] => 0 [guid] => http://new.murakami.ua/shop/fudziyama/ [menu_order] => 0 [post_type] => product [post_mime_type] => [comment_count] => 0 [filter] => raw [img_url] => http://new.murakami.ua/wp-content/uploads/Fudziyama.jpg [visibility] => visible [price] => 99.00 [weight] => 210/140/116/180 [energy] => [sku] => 471 [category] => 182 ) ) 

我们无序的感觉到像物体