MvvmCross - how to bind to SelectedItem in iOS TableView? - xamarin

Question

I have a TableView in iOS and, in my ViewModel, I have a property to Selected Item in TableView, but I don't know how to bind the Selected Item for this property. How can I do that? My project is cross-platform. I have an Android project and an iOS project. In Android project, I did the bind:
<Mvx.MvxListView
android:id="#+id/lstViewTasks"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:focusableInTouchMode="true"
android:choiceMode="multipleChoice"
local:MvxBind="ItemsSource Tasks; SelectedItem SelectedTask; ItemClick ShowTaskCommand"
local:MvxItemTemplate="#layout/projectmytasksitem" />
but I can't do a equivalent bind in iOS.
That's my TableViewController:
[Register("ProjectMyTasksViewc")]
public class ProjectMyTasksViews : MvxTableViewController<ProjectMyTasksViewModel>
{
//other things
var source = new MvxSimpleTableViewSource(TableView, ProjectMyTasksItem.Key, ProjectMyTasksItem.Key);
TableView.Source = source;
this.CreateBinding(source).To<ProjectMyTasksViewModel>(viewModel => viewModel.Tasks).Apply();
this.CreateBinding(source).For(s => s.SelectedItem).To<ProjectMyTasksViewModel>(viewModel => viewModel.SelectedTask).Apply();
this.CreateBinding(source).For(tableSource => tableSource.SelectionChangedCommand).To<ProjectMyTasksViewModel>(viewModel => viewModel.ShowTaskCommand).Apply();
}
Here is my ViewModel:
public class ProjectMyTasksViewModel : MvxViewModel
{
public Action ShowTaskCommandAction { get; set; }
private IList<Task> _tasks;
public IList<Task> Tasks
{
get { return _tasks; }
set { _tasks = value; RaisePropertyChanged(() => Tasks); }
}
private Task _selectedTask;
public Task SelectedTask
{
get { return _selectedTask; }
set { _selectedTask = value; RaisePropertyChanged(() => SelectedTask); }
}
private MvxCommand _showTaskCommand;
public MvxCommand ShowTaskCommand
{
get
{
_showTaskCommand = _showTaskCommand ?? (_showTaskCommand = new MvxCommand(ExecuteShowTaskCommand));
return _showTaskCommand;
}
}
private void ExecuteShowTaskCommand()
{
if (!SelectedTask.IsCompleted)
{
ShowTaskCommandAction?.Invoke();
}
}
}

Answer 1

I believe it has to do with the timing of your ShowTaskCommand getting executed vs the set of SelectedTask. So if you commented out the code inside ExecuteShowTaskCommand and place a breakpoint inside ExecuteShowTaskCommand as well as the set of SelectedTask you would find that the ExecuteShowTaskCommand is running first and then the set of the SelectedTask.
Alternative implementation
To avoid the timing issue you can instead pass the selected task into your command as a parameter.
MvxCommand<Task> _showTaskCommand;
public MvxCommand<Task> ShowTaskCommand =>
_showTaskCommand ?? (_showTaskCommand = new MvxCommand<Task>(ExecuteShowTaskCommand));
private void ExecuteShowTaskCommand(Task selectedTask)
{
if (!selectedTask.IsCompleted)
{
ShowTaskCommandAction?.Invoke();
}
}