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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
namespace Xamarin.Forms
{
internal class ToolbarTracker
{
int _masterDetails;
Page _target;
public IEnumerable<Page> AdditionalTargets { get; set; }
public bool HaveMasterDetail
{
get { return _masterDetails > 0; }
}
public bool SeparateMasterDetail { get; set; }
public Page Target
{
get { return _target; }
set
{
if (_target == value)
return;
UntrackTarget(_target);
_target = value;
if (_target != null)
TrackTarget(_target);
EmitCollectionChanged();
}
}
public IEnumerable<ToolbarItem> ToolbarItems
{
get
{
if (Target == null)
return Enumerable.Empty<ToolbarItem>();
IEnumerable<ToolbarItem> items = GetCurrentToolbarItems(Target);
if (AdditionalTargets != null)
items = items.Concat(AdditionalTargets.SelectMany(t => t.ToolbarItems));
return items.OrderBy(ti => ti.Priority);
}
}
public event EventHandler CollectionChanged;
void EmitCollectionChanged()
{
if (CollectionChanged != null)
CollectionChanged(this, EventArgs.Empty);
}
IEnumerable<ToolbarItem> GetCurrentToolbarItems(Page page)
{
var result = new List<ToolbarItem>();
result.AddRange(page.ToolbarItems);
if (page is MasterDetailPage)
{
var masterDetail = (MasterDetailPage)page;
if (SeparateMasterDetail)
{
if (masterDetail.IsPresented)
{
if (masterDetail.Master != null)
result.AddRange(GetCurrentToolbarItems(masterDetail.Master));
}
else
{
if (masterDetail.Detail != null)
result.AddRange(GetCurrentToolbarItems(masterDetail.Detail));
}
}
else
{
if (masterDetail.Master != null)
result.AddRange(GetCurrentToolbarItems(masterDetail.Master));
if (masterDetail.Detail != null)
result.AddRange(GetCurrentToolbarItems(masterDetail.Detail));
}
}
else if (page is IPageContainer<Page>)
{
var container = (IPageContainer<Page>)page;
if (container.CurrentPage != null)
result.AddRange(GetCurrentToolbarItems(container.CurrentPage));
}
return result;
}
void OnChildAdded(object sender, ElementEventArgs eventArgs)
{
var page = eventArgs.Element as Page;
if (page == null)
return;
RegisterChildPage(page);
}
void OnChildRemoved(object sender, ElementEventArgs eventArgs)
{
var page = eventArgs.Element as Page;
if (page == null)
return;
UnregisterChildPage(page);
}
void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
{
EmitCollectionChanged();
}
void OnPropertyChanged(object sender, PropertyChangedEventArgs propertyChangedEventArgs)
{
if (propertyChangedEventArgs.PropertyName == NavigationPage.CurrentPageProperty.PropertyName || propertyChangedEventArgs.PropertyName == MasterDetailPage.IsPresentedProperty.PropertyName ||
propertyChangedEventArgs.PropertyName == "Detail" || propertyChangedEventArgs.PropertyName == "Master")
{
EmitCollectionChanged();
}
}
void RegisterChildPage(Page page)
{
if (page is MasterDetailPage)
_masterDetails++;
((ObservableCollection<ToolbarItem>)page.ToolbarItems).CollectionChanged += OnCollectionChanged;
page.PropertyChanged += OnPropertyChanged;
}
void TrackTarget(Page page)
{
if (page == null)
return;
if (page is MasterDetailPage)
_masterDetails++;
((ObservableCollection<ToolbarItem>)page.ToolbarItems).CollectionChanged += OnCollectionChanged;
page.Descendants().OfType<Page>().ForEach(RegisterChildPage);
page.DescendantAdded += OnChildAdded;
page.DescendantRemoved += OnChildRemoved;
page.PropertyChanged += OnPropertyChanged;
}
void UnregisterChildPage(Page page)
{
if (page is MasterDetailPage)
_masterDetails--;
((ObservableCollection<ToolbarItem>)page.ToolbarItems).CollectionChanged -= OnCollectionChanged;
page.PropertyChanged -= OnPropertyChanged;
}
void UntrackTarget(Page page)
{
if (page == null)
return;
if (page is MasterDetailPage)
_masterDetails--;
((ObservableCollection<ToolbarItem>)page.ToolbarItems).CollectionChanged -= OnCollectionChanged;
page.Descendants().OfType<Page>().ForEach(UnregisterChildPage);
page.DescendantAdded -= OnChildAdded;
page.DescendantRemoved -= OnChildRemoved;
page.PropertyChanged -= OnPropertyChanged;
}
}
}
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