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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Threading.Tasks;
namespace Xamarin.Forms
{
public abstract class Cell : Element
{
public static readonly BindableProperty IsEnabledProperty = BindableProperty.Create("IsEnabled", typeof(bool), typeof(Cell), true, propertyChanged: OnIsEnabledPropertyChanged);
ObservableCollection<MenuItem> _contextActions;
double _height = -1;
bool _nextCallToForceUpdateSizeQueued;
public IList<MenuItem> ContextActions
{
get
{
if (_contextActions == null)
{
_contextActions = new ObservableCollection<MenuItem>();
_contextActions.CollectionChanged += OnContextActionsChanged;
}
return _contextActions;
}
}
public bool HasContextActions
{
get { return _contextActions != null && _contextActions.Count > 0 && IsEnabled; }
}
public double Height
{
get { return _height; }
set
{
if (_height == value)
return;
OnPropertyChanging("Height");
OnPropertyChanging("RenderHeight");
_height = value;
OnPropertyChanged("Height");
OnPropertyChanged("RenderHeight");
}
}
public bool IsEnabled
{
get { return (bool)GetValue(IsEnabledProperty); }
set { SetValue(IsEnabledProperty, value); }
}
public double RenderHeight
{
get
{
var table = RealParent as TableView;
if (table != null)
return table.HasUnevenRows && Height > 0 ? Height : table.RowHeight;
var list = RealParent as ListView;
if (list != null)
return list.HasUnevenRows && Height > 0 ? Height : list.RowHeight;
return 40;
}
}
public event EventHandler Appearing;
public event EventHandler Disappearing;
public void ForceUpdateSize()
{
if (_nextCallToForceUpdateSizeQueued)
return;
if ((Parent as ListView)?.HasUnevenRows == true)
{
_nextCallToForceUpdateSizeQueued = true;
OnForceUpdateSizeRequested();
}
}
public event EventHandler Tapped;
protected internal virtual void OnTapped()
{
if (Tapped != null)
Tapped(this, EventArgs.Empty);
}
protected virtual void OnAppearing()
{
EventHandler handler = Appearing;
if (handler != null)
handler(this, EventArgs.Empty);
}
protected override void OnBindingContextChanged()
{
base.OnBindingContextChanged();
if (HasContextActions)
{
for (var i = 0; i < _contextActions.Count; i++)
SetInheritedBindingContext(_contextActions[i], BindingContext);
}
}
protected virtual void OnDisappearing()
{
EventHandler handler = Disappearing;
if (handler != null)
handler(this, EventArgs.Empty);
}
protected override void OnParentSet()
{
if (RealParent != null)
{
RealParent.PropertyChanged += OnParentPropertyChanged;
RealParent.PropertyChanging += OnParentPropertyChanging;
}
base.OnParentSet();
}
protected override void OnPropertyChanging(string propertyName = null)
{
if (propertyName == "Parent")
{
if (RealParent != null)
{
RealParent.PropertyChanged -= OnParentPropertyChanged;
RealParent.PropertyChanging -= OnParentPropertyChanging;
}
}
base.OnPropertyChanging(propertyName);
}
internal event EventHandler ForceUpdateSizeRequested;
internal void SendAppearing()
{
OnAppearing();
var container = RealParent as IListViewController;
if (container != null)
container.SendCellAppearing(this);
}
internal void SendDisappearing()
{
OnDisappearing();
var container = RealParent as IListViewController;
if (container != null)
container.SendCellDisappearing(this);
}
void OnContextActionsChanged(object sender, NotifyCollectionChangedEventArgs e)
{
for (var i = 0; i < _contextActions.Count; i++)
SetInheritedBindingContext(_contextActions[i], BindingContext);
OnPropertyChanged("HasContextActions");
}
async void OnForceUpdateSizeRequested()
{
// don't run more than once per 16 milliseconds
await Task.Delay(TimeSpan.FromMilliseconds(16));
EventHandler handler = ForceUpdateSizeRequested;
if (handler != null)
handler(this, null);
_nextCallToForceUpdateSizeQueued = false;
}
static void OnIsEnabledPropertyChanged(BindableObject bindable, object oldvalue, object newvalue)
{
(bindable as Cell).OnPropertyChanged("HasContextActions");
}
void OnParentPropertyChanged(object sender, PropertyChangedEventArgs e)
{
// Technically we might be raising this even if it didn't change, but I'm taking the bet that
// its uncommon enough that we don't want to take the penalty of N GetValue calls to verify.
if (e.PropertyName == "RowHeight")
OnPropertyChanged("RenderHeight");
}
void OnParentPropertyChanging(object sender, PropertyChangingEventArgs e)
{
if (e.PropertyName == "RowHeight")
OnPropertyChanging("RenderHeight");
}
}
}
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