public MainPage()
{
InitializeComponent();
//Set binding context
vm = new MainPageViewModel(this);
BindingContext = vm;
// Hook up event handlers
PlanetListView.SelectionMode = ListViewSelectionMode.Single; //Default
PlanetListView.ItemTapped += PlanetListView_ItemTapped; //User tapped
PlanetListView.ItemSelected += PlanetListView_ItemSelected; //Selection changed
// *****************************************************************
// DATA TEMPLATE
// *****************************************************************
//Data template will instantiate a cell "when required"
//Two options: I like the second but the first is more common
//DataTemplate DataTemplate = new DataTemplate(typeof(TextCell));
DataTemplate dataTemplate = new DataTemplate(() =>
{
//Return a subclass of Cell
TextCell cell = new TextCell();
//We can set properties on cell
MenuItem m1 = new MenuItem
{
Text = "Delete",
IsDestructive = true
};
//Commanding - command is bound directly to the ICommand DeleteCommand = DeleteCommand<SolPlanet> property in ViewModel
//This presumably uses reflection to determine the parameter type
m1.SetBinding(MenuItem.CommandProperty, new Binding("DeleteCommand", source: this.BindingContext));
// See https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/listview/interactivity#context-actions
// The BindingContext for m1 is the data behind the cell (a specific element in the itemsource of the listview)
// See last para on p559 of the book by Charles Petzold
m1.SetBinding(MenuItem.CommandParameterProperty, new Binding("."));
// Or you could use an event handler
/*
* m1.Clicked += (object sender, System.EventArgs e) => {
* //Note that conditional statements evaluate left to right - && will short-circuit if the first condition is not true
* if ((sender is MenuItem mi) && (mi.CommandParameter is SolPlanet p))
* {
* Debug.WriteLine($"Vogons are destroying {p.Name}");
* vm.DeleteItem(p);
* }
* };
*/
//Add menu item to the cell
cell.ContextActions.Add(m1);
return(cell);
});
//Binding proxy: When the DataTemplate instantiates a cell, it will also set up the binding as specified below
//The source will be a data elelement
dataTemplate.SetBinding(TextCell.TextProperty, "Name");
dataTemplate.SetBinding(TextCell.DetailProperty, "Distance");
//Finally, set the ItemTemplate property (type DataTemplate)
PlanetListView.ItemTemplate = dataTemplate;
// *****************************************************************
}
