xamarin.forms加载指示器未显示

Question

在我的xamarin.forms应用程序中，我使用 Acr.Userdialogs 来显示加载指示符。我试图做的是单击一个按钮时将执行一个同步方法。 api将调用并根据api结果从该页面进行导航。api调用和导航工作正常。但是我无法使用Acr.user对话框显示加载指示器。应该是什么问题？我应该在 Device.BeginInvokeOnMainThread 上运行整个方法吗？请指教。

我的按钮点击

  private  void submit_clicked(object sender, EventArgs args)
        {
            UserDialogs.Instance.ShowLoading("Submitting data...");
            SubmitData();
        }
        private void SubmitData()
        {            
                 if (userMappedStateListData.Entry[0].State.Contains(State_picker.Text))
                 {
                    try
                    {
                       //<=================My API CALL =======================>

                            ............................................
                            ............................................
                            ............................................



                      // Result of Api is placed in a list called transactions


                        if (transactions[0].Questions.Count < 5)
                        {
                            UserDialogs.Instance.HideLoading();                           
                            PopupNavigation.PushAsync(new NoDataPopUp());
                        }
                        else
                        {
                            foreach (Question ques in transactions[0].Questions)
                            {
                                foreach (Answer ans in ques.Answers)
                                {
                                    if (ans.Text != CommonValues.none && ans.Correct == true)
                                    {
                                        ObjQuestionData.Add(ques);
                                        truequescount = ObjQuestionData.Count.ToString();
                                    }
                                }
                            }
                            if (ObjQuestionData.Count < 1)
                            {                              
                                UserDialogs.Instance.HideLoading();                       
                                PopupNavigation.PushAsync(new InsuffQdata());

                            }
                            else
                            {
                                foreach (Question ques in transactions[0].Questions)
                                {
                                    if (ObjQuestionData.Count < 5)
                                    {
                                        foreach (Answer ans in ques.Answers)
                                        {
                                            if (ans.Text == CommonValues.none && ans.Correct == true)
                                            {
                                                ObjQuestionData.Add(ques);
                                            }
                                        }
                                    }
                                }
                            }
                        }
                        Tranzaction tranzaction = new Tranzaction()
                        {
                            TransactionId = transactions[0].TransactionId,
                            Questions = ObjQuestionData.GetRange(0, 5)
                        };

                        List<String> formdata = new List<String>() { first_name.Text, last_name.Text, street_name.Text, State_picker.Text, zip_code.Text, SSN.Text, BAN.Text, truequescount };

                            UserDialogs.Instance.HideLoading();                  
                            Navigation.PushAsync(new SecurityQuestionScreen(tranzaction, formdata));

                    }
                    catch (Exception)
                    {
                    }
                }
                else
                {
                    try
                    {
                        List<String> formdata = new List<String>() { first_name.Text, last_name.Text, street_name.Text, State_picker.Text, zip_code.Text, SSN.Text, BAN.Text };


                            UserDialogs.Instance.HideLoading();
                            PopupNavigation.PushAsync(new FormVerificationPopup(formdata));                 
                    }
                    catch (Exception ex)
                    {
                    }
                }
        }

Answer 1

如果您在线程中具有UI交互，则可以通过Device.BeginInvokeOnMainThread来实现。

private void Button_Clicked(object sender, EventArgs e)
    {
        UserDialogs.Instance.ShowLoading("Submitting data...");
        Task.Run(async () =>
        {
            // Run code here
             await Task.Delay(4000);
            Device.BeginInvokeOnMainThread(() =>
            {
                // UI interaction goes here

                UserDialogs.Instance.HideLoading();

            });
        });
    }

有一个相关的博客。 http://lukealderton.com/blog/posts/2016/october/xamarin-forms-working-with-threads/

上传数据

这里是在调用api之后添加一个导航页面。