Question

我有一个listview，其数据来自sqlite数据库。当用户选择上一页的数据来自JSON的列表时，将创建数据库。代码：

ConnectionProfile connections = NetworkInformation.GetInternetConnectionProfile();
            if (connections != null && connections.GetNetworkConnectivityLevel() == NetworkConnectivityLevel.InternetAccess)
            {
                loading.IsIndeterminate = true;

                try
                {
                    string urlPath = "https://.../tryout_perid";
                    var httpClient = new HttpClient(new HttpClientHandler());

                    var values = new List<KeyValuePair<string, string>>
                    {
                        new KeyValuePair<string, string>("tid", ((App)(App.Current)).ID)
                    };

                    var response = await httpClient.PostAsync(urlPath, new FormUrlEncodedContent(values));
                    response.EnsureSuccessStatusCode();

                    if (!response.IsSuccessStatusCode)
                    {
                        loading.IsIndeterminate = false;
                        RequestException();
                    }
                    string jsonText = await response.Content.ReadAsStringAsync();
                    JsonObject jsonObject = JsonObject.Parse(jsonText);
                    JsonArray jsonData = jsonObject["data"].GetArray();

                    foreach (JsonValue groupValue1 in jsonData)
                    {
                        JsonObject groupObject2 = groupValue1.GetObject();
                        string id = groupObject2["id"].GetString();
                        string title = groupObject2["judul"].GetString();

                        QuizHome quiz = new QuizHome();
                        quiz.ID = id;
                        ((App)(App.Current)).ID = quiz.ID.ToString();
                        quiz.Title = title;
                        quizDataSource.Add(quiz);

                        if (quizDataSource.Count > 0)
                        {
                            string InsertQuiz = @"INSERT INTO DBName (ID,Judul) SELECT '" + id.ToString() + "','" + title.ToString() + "','" + "' WHERE not exists " +
                                "(select ID and Judul FROM DBName WHERE ID='" + id.ToString() + "' and Judul='" + title.ToString() + "')";
                            var quizName = objConn.Prepare(InsertQuiz);
                            quizName.Step();
                        }

                        JsonArray jsonDataSoal = groupObject2["list_soal"].GetArray();
                        foreach (JsonValue groupValueSoal in jsonDataSoal)
                        {
                            JsonObject groupObjectSoal = groupValueSoal.GetObject();

                            string qid = groupObjectSoal["qid"].GetString();
                            string pertanyaan = groupObjectSoal["question"].GetString();

                            QuizQuestion question = new QuizQuestion();
                            question.QID = qid;
                            question.Pertanyaan = pertanyaan;
                            questionDataSource.Add(question);

                            if (questionDataSource.Count > 0)
                            {
                                string InsertQuestion = @"INSERT INTO DBQuestion (QID,Pertanyaan) SELECT '" + qid.ToString() + "','" + pertanyaan.ToString() + "' WHERE not exists " +
                                    "(select QID and Pertanyaan FROM DBQuestion WHERE OID='" + qid.ToString() + "' and Pertanyaan='" + pertanyaan.ToString() + "')";
                                var quizQuestion = objConn.Prepare(InsertQuestion);
                                quizQuestion.Step();
                            }

                            JsonArray jsonDataOption = groupObjectSoal["jawaban"].GetArray();
                            foreach (JsonValue groupValueOption in jsonDataOption)
                            {
                                JsonObject groupObjectOption = groupValueOption.GetObject();

                                string oid = groupObjectOption["oid"].GetString();
                                string option = groupObjectOption["q_option"].GetString();
                                string score = groupObjectOption["score"].GetString();

                                QuizOption pilihan = new QuizOption();
                                pilihan.OID = oid;
                                pilihan.Option = option;
                                optionDataSource.Add(pilihan);

                                if (optionDataSource.Count > 0)
                                {
                                    string InsertOption = @"INSERT INTO DBOption (OID,Option) SELECT '" + oid.ToString() + "','" + option.ToString() + "','" + "' WHERE not exists " +
                                        "(select OID and Option FROM DBOption WHERE OID='" + oid.ToString() + "' and Option='" + option.ToString() + "')";
                                    var quizOption = objConn.Prepare(InsertOption);
                                    quizOption.Step();
                                }
                            }
                        }
                        this.Loaded += ReadTryoutList_Loaded;
                        loading.IsIndeterminate = false;
                    }
                }

private void ReadTryoutList_Loaded(object sender, RoutedEventArgs e)
        {
            ReadAllDBName dbName = new ReadAllDBName();
            DB_TryoutList = dbName.GetAllDBName();
            ListTryout.ItemsSource = DB_TryoutList.OrderByDescending(i => i.ID).ToList();//Binding DB data to LISTBOX and Latest contact ID can Display first.  
            if (DB_TryoutList.Count == 0)
            {
                statuskosongStack.Visibility = Visibility.Visible;
                ListTryout.Visibility = Visibility.Collapsed;
            }
            else
            {
                statuskosongStack.Visibility = Visibility.Collapsed;
                ListTryout.Visibility = Visibility.Visible;
            }
        }

我遇到了问题，即当用户选择上一页上的列表并且数据已成功存储在数据库中时，但listview上的数据量不会增加。如果我单击后退按钮并再次在此页面上输入，则listview上的数据会增加。如何在成功保存数据时使listview增加数据量？

Answer 1

此问题是由代码中的异步方法引起的。单击该项后，导航到TryoutLibrary1页面。在此页面上，您将数据保存到数据库，同时从Page.Loaded事件中获取数据库中的数据源。但是当您获得数据时，单击的项目尚未插入到数据库中，因此在您重新加载数据之前它不会显示在页面上（再次重新输入页面）。

因此，您应该在ItemClick事件中重新考虑您的逻辑，您应该确保数据已保存到数据库中，然后您将数据设置为ListView.ItemsSource。例如，当您单击该项时，您可以创建一个对象并将其放入本地ObservableCollection对象，然后将ObservableCollection设置为ListView itemsSource以使其显示在UI上，在其他您可以将项目保存到数据库中。

当数据成功存储在uwp

1 个答案: