我正在使用xamarin表格。我试图在日历控件中绑定Web服务。请参阅以下日历控件链接（XamForms.Controls.Calendar）。
https://github.com/rebeccaXam/XamForms.Controls.Calendar
第一个功能是创建7 * 6 = 42个标签和按钮，然后使用“callWebService”方法调用服务函数，这是异步方法从服务获取响应。
protected void FillCalendarWindows()
{
try
{
for (int r = 0; r < 6; r++)
{
for (int c = 0; c < 7; c++)
{
if (r == 0)
{
labels.Add(new Label
{
HorizontalOptions = LayoutOptions.Center,
VerticalOptions = LayoutOptions.Center,
TextColor = Color.Black,
FontSize = 18,
FontAttributes = FontAttributes.Bold
});
DayLabels.Children.Add(labels.Last(), c, r);
}
buttons.Add(new CalendarButton
{
BorderRadius = 0,
BorderWidth = BorderWidth,
BorderColor = BorderColor,
FontSize = DatesFontSize,
BackgroundColor = DatesBackgroundColor,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand
});
buttons.Last().Clicked += DateClickedEvent;
MainCalendar.Children.Add(buttons.Last(), c, r);
}
}
flag = 1;
//Device.BeginInvokeOnMainThread(() => CallWebService(StartDate.Month, StartDate.Year));
CallWebService(StartDate.Month, StartDate.Year);
//CallServiceInNewTask(StartDate.Month, StartDate.Year);
//Device.BeginInvokeOnMainThread(() => ChangeCalendar(CalandarChanges.All));
}
catch (Exception e)
{
}
}
第二个函数是“callWebService”函数，我在列表集合对象中收集响应然后调用“ChangeClaendar”函数，该函数用于绑定标签和按钮文本并填充适当的颜色。
public async void CallWebService(int Month, int Year)
{
try
{
var response = await GetResponseFromWebService.GetResponse<ServiceClasses.RootObject_AttendanceTable>(ServiceURL.GetAttendanceTableList + "Month=" + Month + "&Year=" + Year + "&EmpCd=" + _empCode);
if (response.Flag == true)
{
if (ListObjAttendanceTblList == null)
{
ListObjAttendanceTblList = new List<LstAttendanceDtl>();
}
for (int i = 0; i < response.lstAttendanceDtl.Count; i++)
{
var objAttendanceTableList = new LstAttendanceDtl();
objAttendanceTableList.AttendanceDt = response.lstAttendanceDtl[i].AttendanceDt;
objAttendanceTableList.EarlyDeparture = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.InTime = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.LateArrival = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.OutTime = response.lstAttendanceDtl[i].OutTime;
objAttendanceTableList.OverTime = response.lstAttendanceDtl[i].OverTime;
objAttendanceTableList.Reason = response.lstAttendanceDtl[i].Reason;
objAttendanceTableList.Remark = response.lstAttendanceDtl[i].Remark;
objAttendanceTableList.Shift = response.lstAttendanceDtl[i].Shift;
objAttendanceTableList.WorkingHrs = response.lstAttendanceDtl[i].WorkingHrs;
ListObjAttendanceTblList.Add(objAttendanceTableList);
}
}
else
{
}
if (flag == 1)
{
ChangeCalendar(CalandarChanges.All);
}
else
{
ChangeCalendar(CalandarChanges.StartDate);
}
}
catch (WebException e)
{
}
}
第三个功能是“ChangeCalendar”
protected void ChangeCalendar(CalandarChanges changes)
{
try
{
if (changes.HasFlag(CalandarChanges.StartDate))
{
Device.BeginInvokeOnMainThread(() => CenterLabel.Text = StartDate.ToString(TitleLabelFormat));
}
var start = CalendarStartDate;
var beginOfMonth = false;
var endOfMonth = false;
for (int i = 0; i < buttons.Count; i++)
{
endOfMonth |= beginOfMonth && start.Day == 1;
beginOfMonth |= start.Day == 1;
LstAttendanceDtl objAttendanceDtl = ListObjAttendanceTblList.Find(s => s.AttendanceDt.Equals(start.Date.ToString("dd/MM/yyyy")));
string remarks = string.Empty;
if (i < 7 && WeekdaysShow && changes.HasFlag(CalandarChanges.StartDay))
{
Device.BeginInvokeOnMainThread(() => labels[i].Text = start.ToString(WeekdaysFormat));
//labels[i].Text = start.ToString(WeekdaysFormat);
//DateTime d = Convert.ToDateTime(objAttendanceDtl.AttendanceDt).Date;
}
if (changes.HasFlag(CalandarChanges.All))
{
Device.BeginInvokeOnMainThread(()=>buttons[i].Text = string.Format("{0}", start.Day));
//buttons[i].Text = string.Format("{0}", start.Day);
}
else
{
Device.BeginInvokeOnMainThread(() => buttons[i].TextWithoutMeasure = string.Format("{0}", start.Day));
}
buttons[i].Date = start;
var isInsideMonth = beginOfMonth && !endOfMonth;
if (objAttendanceDtl != null)
{
remarks = objAttendanceDtl.Remark;
if ((remarks.ToLower()).Trim() == stringFullDay.ToLower().Trim())
{
SetButtonPresent(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringAbsent.ToLower().Trim())
{
SetButtonAbsent(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringWeekOff.ToLower().Trim())
{
SetButtonWeekendMood(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringHolidays.ToLower().Trim())
{
SetButtonHolidays(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringSecondhalfAbsent.ToLower().Trim() ||
remarks.ToLower().Trim() == stringFirsthalfAbsent.ToLower().Trim())
{
SetButtonHalfDayMood(buttons[i], isInsideMonth);
}
else
{
SetButtonDisabled(buttons[i]);
}
}
else
{
SetButtonOutSideMonth(buttons[i]);
}
SpecialDate sd = null;
if (SpecialDates != null)
{
sd = SpecialDates.FirstOrDefault(s => s.Date.Date == start.Date);
}
if (sd != null)
{
SetButtonSpecial(buttons[i], sd);
}
else if (SelectedDate.HasValue && start.Date == SelectedDate.Value.Date)
{
SetButtonSelected(buttons[i], isInsideMonth);
}
start = start.AddDays(1);
}
}
catch (Exception e)
{
}
}
问题是：
1。当我尝试直接填写标签列表时，在“Changecalendar”功能中
labels[i].Text = start.ToString(WeekdaysFormat);
它向我显示错误
“UIKit一致性错误：您正在调用只能从UI线程调用的UIKit方法。”所以要删除此错误，我写了
Device.BeginInvokeOnMainThread(() => labels[i].Text = start.ToString(WeekdaysFormat));
Device.BeginInvokeOnMainThread(()=>buttons[i].Text = string.Format("{0}", start.Day));
Device.BeginInvokeOnMainThread(() => buttons[i].TextWithoutMeasure = string.Format("{0}", start.Day));
但它显示错误
System.ArgumentOutOfRangeException：索引超出范围。必须是非负数且小于集合的大小。
2. 如果我把“FillCalendarWindow”中的函数“CallWebService”和“ChangeCalendar”一个接一个地放入，那么列表对象没有绑定，控件就是从函数中出来而直接用ChangeCalendar函数调用并给我空引用对象。
答案 0 :(得分：3)
该问题未提供测试解决方案所需的完整源代码。
回答关于在非异步方法中调用等待函数的问题。你可以使用
CallWebService().Wait(optional timeout);
或
CallWebService().GetAwaiter().GetResult();
您还应该更改功能定义
async void CallWebService(int Month, int Year)
到
async Task CallWebService(int Month, int Year);
正确处理异常和线程切换
如果您可以不阻止地调用CallWebService，那么您也可以
CallWebService(1,2).ContinueWith((task) =>
{
});
答案 1 :(得分：2)
我假设从UI线程调用FillCalendarWindows（）方法，但是你不希望UI线程在外部操作GetResponseFromWebService.GetResponse发生时等待并冻结控件，这就是你在等待的原因CallWebService（）内部的异步调用。
我认为使用异步CallWebService的更好方法是使用“async all as”，因此您必须将CallWebService上游的所有方法更改为异步方法。这有一个额外的好处，你不需要做Device.BeginInvokeOnMainThread，因为async / await捕获调用者的同步上下文，因此将在UI线程上调用ChangeCalendar。
async void SomeEventHandler()
{
// called from the UI thread (or its equivalent in Xamarin)
await FillCalendarWindows();
}
protected async Task FillCalendarWindows()
{
try
{
//create 7*6 = 42 labels and buttons
await CallWebService(StartDate.Month, StartDate.Year);
}
catch (Exception e)
{
}
}
public async Task CallWebService(int Month, int Year)
{
try
{
await GetResponseFromWebService.GetResponse... ;
// .... same code as in your example
ChangeCalendar(....);
}
catch /*... */
{
}
}
protected void ChangeCalendar(int changes)
{
try
{
/* no need to do Device.BeginInvokeOnMainThread () so you can replace all that with normal calls*/
}
catch (Exception e)
{
/* ... */
}
}
不确定如何引发System.ArgumentOutOfRangeException，我无法在github上找到正确的代码版本，因此我无法调查该特定错误。我的猜测是你有多个线程修改“按钮”集合，当你调用Device.BeginInvokeOnMainThread时，你可能会发现集合的元素少于预期。
TL; DR：一直使用async / await而不是以同步方式调用异步方法，这样可以更容易地找到问题的原因
答案 2 :(得分：2)
尝试以下
protected async Task FillCalendarWindows()
{
try
{
for (int r = 0; r < 6; r++)
{
for (int c = 0; c < 7; c++)
{
if (r == 0)
{
labels.Add(new Label
{
HorizontalOptions = LayoutOptions.Center,
VerticalOptions = LayoutOptions.Center,
TextColor = Color.Black,
FontSize = 18,
FontAttributes = FontAttributes.Bold
});
DayLabels.Children.Add(labels.Last(), c, r);
}
buttons.Add(new CalendarButton
{
BorderRadius = 0,
BorderWidth = BorderWidth,
BorderColor = BorderColor,
FontSize = DatesFontSize,
BackgroundColor = DatesBackgroundColor,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand
});
buttons.Last().Clicked += DateClickedEvent;
MainCalendar.Children.Add(buttons.Last(), c, r);
}
}
flag = 1;
//Device.BeginInvokeOnMainThread(() => CallWebService(StartDate.Month, StartDate.Year));
await CallWebService(StartDate.Month, StartDate.Year);
//CallServiceInNewTask(StartDate.Month, StartDate.Year);
//Device.BeginInvokeOnMainThread(() => await ChangeCalendar(CalandarChanges.All));
}
catch (Exception e)
{
}
}
您的网络服务应该像
public async Task CallWebService(int Month, int Year)
{
try
{
var response = await GetResponseFromWebService.GetResponse<ServiceClasses.RootObject_AttendanceTable>(ServiceURL.GetAttendanceTableList + "Month=" + Month + "&Year=" + Year + "&EmpCd=" + _empCode);
if (response.Flag == true)
{
if (ListObjAttendanceTblList == null)
{
ListObjAttendanceTblList = new List<LstAttendanceDtl>();
}
for (int i = 0; i < response.lstAttendanceDtl.Count; i++)
{
var objAttendanceTableList = new LstAttendanceDtl();
objAttendanceTableList.AttendanceDt = response.lstAttendanceDtl[i].AttendanceDt;
objAttendanceTableList.EarlyDeparture = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.InTime = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.LateArrival = response.lstAttendanceDtl[i].EarlyDeparture;
objAttendanceTableList.OutTime = response.lstAttendanceDtl[i].OutTime;
objAttendanceTableList.OverTime = response.lstAttendanceDtl[i].OverTime;
objAttendanceTableList.Reason = response.lstAttendanceDtl[i].Reason;
objAttendanceTableList.Remark = response.lstAttendanceDtl[i].Remark;
objAttendanceTableList.Shift = response.lstAttendanceDtl[i].Shift;
objAttendanceTableList.WorkingHrs = response.lstAttendanceDtl[i].WorkingHrs;
ListObjAttendanceTblList.Add(objAttendanceTableList);
}
}
else
{
}
if (flag == 1)
{
await ChangeCalendar(CalandarChanges.All);
}
else
{
await ChangeCalendar(CalandarChanges.StartDate);
}
}
catch (WebException e)
{
}
}
你的ChnageCalender方法应该像
protected async Task ChangeCalendar(CalandarChanges changes)
{
try
{
if (changes.HasFlag(CalandarChanges.StartDate))
{
Device.BeginInvokeOnMainThread(() => CenterLabel.Text = StartDate.ToString(TitleLabelFormat));
}
var start = CalendarStartDate;
var beginOfMonth = false;
var endOfMonth = false;
for (int i = 0; i < buttons.Count; i++)
{
endOfMonth |= beginOfMonth && start.Day == 1;
beginOfMonth |= start.Day == 1;
LstAttendanceDtl objAttendanceDtl = ListObjAttendanceTblList.Find(s => s.AttendanceDt.Equals(start.Date.ToString("dd/MM/yyyy")));
string remarks = string.Empty;
if (i < 7 && WeekdaysShow && changes.HasFlag(CalandarChanges.StartDay))
{
Device.BeginInvokeOnMainThread(() => labels[i].Text = start.ToString(WeekdaysFormat));
//labels[i].Text = start.ToString(WeekdaysFormat);
//DateTime d = Convert.ToDateTime(objAttendanceDtl.AttendanceDt).Date;
}
if (changes.HasFlag(CalandarChanges.All))
{
Device.BeginInvokeOnMainThread(()=>buttons[i].Text = string.Format("{0}", start.Day));
//buttons[i].Text = string.Format("{0}", start.Day);
}
else
{
Device.BeginInvokeOnMainThread(() => buttons[i].TextWithoutMeasure = string.Format("{0}", start.Day));
}
buttons[i].Date = start;
var isInsideMonth = beginOfMonth && !endOfMonth;
if (objAttendanceDtl != null)
{
remarks = objAttendanceDtl.Remark;
if ((remarks.ToLower()).Trim() == stringFullDay.ToLower().Trim())
{
SetButtonPresent(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringAbsent.ToLower().Trim())
{
SetButtonAbsent(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringWeekOff.ToLower().Trim())
{
SetButtonWeekendMood(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringHolidays.ToLower().Trim())
{
SetButtonHolidays(buttons[i], isInsideMonth);
}
else if (remarks.ToLower().Trim() == stringSecondhalfAbsent.ToLower().Trim() ||
remarks.ToLower().Trim() == stringFirsthalfAbsent.ToLower().Trim())
{
SetButtonHalfDayMood(buttons[i], isInsideMonth);
}
else
{
SetButtonDisabled(buttons[i]);
}
}
else
{
SetButtonOutSideMonth(buttons[i]);
}
SpecialDate sd = null;
if (SpecialDates != null)
{
sd = SpecialDates.FirstOrDefault(s => s.Date.Date == start.Date);
}
if (sd != null)
{
SetButtonSpecial(buttons[i], sd);
}
else if (SelectedDate.HasValue && start.Date == SelectedDate.Value.Date)
{
SetButtonSelected(buttons[i], isInsideMonth);
}
start = start.AddDays(1);
}
}
catch (Exception e)
{
}
}
答案 3 :(得分：1)
我发现你的评论中至少有两个问题
＆＃34;如果（response.flag == true）（控件退出该功能）并直接调用ChangeCalendar（） - 显然是因为您没有等待。
您的按钮数量（42）与标签数量（7）不同，所以当您尝试使用相同的标签[i]和按钮[i]时，＃34; i＆＃34 ;您正在获得标签索引的ArgumentOutOfRangeException。注意if(r==0)将标签数限制为7。
for (int r = 0; r < 6; r++)
{
for (int c = 0; c < 7; c++)
{
if (r == 0)
{
labels.Add(new Label