希望有人可以幫助我以下,因爲我完全卡住了。「System.InvalidOperationException:集合被修改」在MvvmCross TableView綁定
當我在我的TableView上綁定時,我在我的MvvmCross Xamarin.iOS應用程序中收到下面的異常。這隻發生在我更改數據源時(每次更改日期時,TableView都需要更新)。
Incident Identifier: 7E7C2B15-7CC4-4AE7-9891-C4FD82358009
CrashReporter Key: 46CC21C0-DDE1-4313-9658-EC79D767939B
Hardware Model: iPhone7,2
Process: UurwerkiOS [4326]
Path: /var/containers/Bundle/Application/75969477-A516-44C3-A5A3-5B24DDDC89C8/UurwerkiOS.app/UurwerkiOS
Identifier: com.route2it.uurwerk
Version: 1.0 (1.0.96)
Code Type: ARM-64
Parent Process: ??? [1]
Date/Time: 2016-07-04T13:16:38Z
Launch Time: 2016-07-04T13:16:31Z
OS Version: iPhone OS 9.3.2 (13F69)
Report Version: 104
Exception Type: SIGABRT
Exception Codes: #0 at 0x1816ac11c
Crashed Thread: 5
Application Specific Information:
*** Terminating app due to uncaught exception 'System.AggregateException', reason: 'System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException (ExceptionResource resource) <0x10044bec0 + 0x00024> in <filename unknown>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare() <0x1003bf900 + 0x0002f> in <filename unknown>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext() <0x1003bf830 + 0x0009f> in <filename unknown>:0
at MvvmCross.Binding.BindingContext.MvxTaskBasedBindingContext.<OnDataContextChange>b__20_0() <0x1007c1990 + 0x0023f> in <filename unknown>:0
at System.Threading.Tasks.Task.InnerInvoke() <0x10043f1f0 + 0x0005f> in <filename unknown>:0
at System.Threading.Tasks.Task.Execute() <0x10043ea20 + 0x00043> in <filename unknown>:0
--- End of inner exception stack trace ---
---> (Inner Exception #0) System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
at System.ThrowHelper.ThrowInvalidOperationException (ExceptionResource resource) <0x10044bec0 + 0x00024> in <filename unknown>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare() <0x1003bf900 + 0x0002f> in <filename unknown>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext() <0x1003bf830 + 0x0009f> in <filename unknown>:0
at MvvmCross.Binding.BindingContext.MvxTaskBasedBindingContext.<OnDataContextChange>b__20_0() <0x1007c1990 + 0x0023f> in <filename unknown>:0
at System.Threading.Tasks.Task.InnerInvoke() <0x10043f1f0 + 0x0005f> in <filename unknown>:0
at System.Threading.Tasks.Task.Execute() <0x10043ea20 + 0x00043> in <filename unknown>:0
起初我以爲它與我的一個Async方法有關(可能在下一個方法已經運行時沒有及時完成)。所以我刪除了所有的異步代碼,但仍然發生異常。我也確保我自己不改變可枚舉集合。我獲取數據(只是內存數組中的數據)並將其作爲新列表返回給TableView綁定的屬性。下面是代碼片段組成的結合(這是一個很大的信息,但我想盡可能完整):
CalendarViewController:
public override void ViewDidLoad()
{
base.ViewDidLoad();
if (NavigationController != null)
NavigationController.NavigationBarHidden = false;
InitCalendar();
InitNavigationItem();
InitTableView();
ApplyConstraints();
var shiftForDateTableViewSource = new MvxSimpleTableViewSource(_tableView, CalendarTableViewCell.Key, CalendarTableViewCell.Key);
shiftForDateTableViewSource.DeselectAutomatically = true;
_tableView.RowHeight = 45;
_tableView.Source = shiftForDateTableViewSource;
var set = this.CreateBindingSet<CalendarView, CalendarViewModel>();
set.Bind(shiftForDateTableViewSource).To(vm => vm.ShiftsForSelectedDate);
set.Bind(shiftForDateTableViewSource).For(vm => vm.SelectionChangedCommand).To(vm => vm.ShiftSelectedCommand);
set.Apply();
_tableView.ReloadData();
}
private void InitTableView()
{
_tableView = new UITableView();
_tableView.RegisterClassForCellReuse(typeof(UITableViewCell), CalendarTableViewCell.Key);
Add(_tableView);
}
CalendarTableViewCell:
public partial class CalendarTableViewCell : MvxTableViewCell
{
public static readonly NSString Key = new NSString("CalendarTableViewCell");
public static readonly UINib Nib;
static CalendarTableViewCell()
{
Nib = UINib.FromName("CalendarTableViewCell", NSBundle.MainBundle);
}
protected CalendarTableViewCell(IntPtr handle) : base(handle)
{
}
public override void LayoutSubviews()
{
base.LayoutSubviews();
var set = this.CreateBindingSet<CalendarTableViewCell, Shift>();
set.Bind(StartTimeLabel).To(vm => vm.StartDate).WithConversion("StringFormat", "HH:mm");
set.Bind(EndTimeLabel).To(vm => vm.EndDate).WithConversion("StringFormat", "HH:mm");
set.Bind(ColorBarView).For("BackgroundColor").To(vm => vm.Color).WithConversion("RGB");
set.Bind(TitleLabel).To(vm => vm).WithConversion("ConcatenatedEventTitle");
set.Bind(LocationLabel).To(vm => vm.Location);
set.Apply();
}
}
CalendarViewModel:
public class CalendarViewModel
: MvxViewModel
{
private readonly IShiftService _shiftService;
public CalendarViewModel(IShiftService shiftService)
{
if (shiftService == null)
throw new ArgumentNullException(nameof(shiftService));
_shiftService = shiftService;
}
public override void Start()
{
base.Start();
Shifts = _shiftService.GetShiftsForEmployeeAsync(1);
}
private IEnumerable<Shift> _shifts;
public IEnumerable<Shift> Shifts
{
get { return _shifts; }
set
{
SetProperty(ref _shifts,
value,
nameof(Shifts));
}
}
private IEnumerable<Shift> _shiftsForSelectedDate;
public IEnumerable<Shift> ShiftsForSelectedDate
{
get { return _shiftsForSelectedDate; }
private set
{
if (_shiftsForSelectedDate == value)
return;
SetProperty(ref _shiftsForSelectedDate,
value,
nameof(ShiftsForSelectedDate));
}
}
private DateTime? _selectedDate;
public DateTime? SelectedDate
{
get { return _selectedDate; }
set
{
if (_selectedDate == value)
return;
SetProperty(ref _selectedDate,
value,
nameof(SelectedDate));
if (_selectedDate.HasValue)
FetchShiftsForSelectedDate();
}
}
private void FetchShiftsForSelectedDate()
{
ShiftsForSelectedDate = _shiftService.GetShiftsForSelectedDateAsync(_selectedDate.Value);
}
}
MockShiftService(實現IShiftService接口):
public class MockShiftService
: IShiftService
{
private IList<Shift> _shifts;
public MockShiftService()
{
Initialize();
}
public IEnumerable<Shift> GetShiftsForEmployeeAsync(int employeeId)
{
return _shifts;
}
public IEnumerable<Shift> GetShiftsForSelectedDateAsync(DateTime selectedDate)
{
var endDate = selectedDate.Date.Add(new TimeSpan(23, 59, 59));
return _shifts
.Where(s => s.StartDate <= endDate && s.EndDate >= selectedDate)
.ToList();
}
public Shift GetShiftByIdAsync(int shiftId)
{
return _shifts.First((shift) => shift.Id == shiftId);
}
private void Initialize()
{
var shifts = new List<Shift>();
// The in memory array gets populated here which
// is straight forward creating instances of the
// 'Shift' class and assigning it's properties before
// adding it to the 'shifts' collection. I left
// this code out to keep it as short as possible.
}
}
UPDATE:
我已經直接引用我的項目MvvmCross的調試組件和想通了,拋出異常在MvxTaskBasedBindingContext
類的127行上,並且總是在第二次迭代中發生。從這我得出結論,集合在第一次迭代期間被改變。不幸的是我不知道爲什麼或如何。
我注意到MvxTaskBasedBindingContext
取代MvxBindingContext
(在11-5-2016由softlion更改)。當我強制我的應用程序使用MvxBindingContext
類時,所有的都很好(雖然有點滯後)。這讓我相信問題出在MvxTaskBasedBindingContext
,但我真的不知道爲什麼,任何幫助將不勝感激。
更新2:
經過一些調試和擺弄周圍,我發現該異常有關,我的CalendarTableViewCell
類設置綁定(應定義在tableview中的每個項目提供佈局我的CalendarViewController
。當我註釋掉CalendarTableViewCell
類中的綁定時,異常不會發生(請參閱上面的代碼)。但我仍然不知道可能是錯誤的。
什麼版本的MvvmCross?我認爲這樣的事情已經解決了。 – Cheesebaron
我在版本4.2.0,4.2.1和4.2.2中遇到此問題。 –
我對iOS不太熟悉,但我注意到的一件事是他們傾向於使用'DelayBind'。因此,也許你的MvxTableViewCell綁定包裹在'this.DelayBind(()=> {/ *你的代碼在LayoutSubviews中綁定在這裏* /});'可能有幫助嗎?純粹的猜測,我不知道iOS如何工作。 – Plac3Hold3r