/
VisualElementPackager.cs
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/
VisualElementPackager.cs
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using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using Xamarin.Forms.Internals;
using Android.Views;
using AView = Android.Views.View;
namespace Xamarin.Forms.Platform.Android
{
public class VisualElementPackager : IDisposable
{
readonly EventHandler<ElementEventArgs> _childAddedHandler;
readonly EventHandler<ElementEventArgs> _childRemovedHandler;
readonly EventHandler _childReorderedHandler;
List<IVisualElementRenderer> _childViews;
Dictionary<BindableObject, VisualElementPackager> _childPackagers;
bool _disposed;
IVisualElementRenderer _renderer;
VisualElement _element;
IElementController ElementController => _element;
public VisualElementPackager(IVisualElementRenderer renderer, VisualElement element = null)
{
if (renderer == null)
throw new ArgumentNullException(nameof(renderer));
_element = element ?? renderer.Element;
_childAddedHandler = OnChildAdded;
_childRemovedHandler = OnChildRemoved;
_childReorderedHandler = OnChildrenReordered;
_renderer = renderer;
_renderer.ElementChanged += OnElementChanged;
if (renderer.View is ILayoutChanges layout)
layout.LayoutChange += OnInitialLayoutChange;
}
void OnInitialLayoutChange(object sender, AView.LayoutChangeEventArgs e)
{
// this is used to adjust any relative elevations on the child elements that still need to settle
// the default elevation is set on Button after it's already added to the view hierarchy
// but this appears to only be the case when the app first starts
if (sender is ILayoutChanges layout)
layout.LayoutChange -= OnInitialLayoutChange;
EnsureChildOrder(true);
}
void OnElementChanged(object sender, VisualElementChangedEventArgs e)
=> SetElement(e.OldElement, e.NewElement);
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (_disposed)
return;
_disposed = true;
if (disposing)
{
if (_renderer != null)
{
_renderer.ElementChanged -= OnElementChanged;
if (_renderer.Element != null)
{
_renderer.Element.ChildAdded -= _childAddedHandler;
_renderer.Element.ChildRemoved -= _childRemovedHandler;
_renderer.Element.ChildrenReordered -= _childReorderedHandler;
}
if (_renderer.View is ILayoutChanges layout)
layout.LayoutChange -= OnInitialLayoutChange;
SetElement(_element, null);
if (_childViews != null)
{
_childViews.Clear();
_childViews = null;
}
if (_childPackagers != null)
{
foreach (var kvp in _childPackagers)
kvp.Value.Dispose();
_childPackagers.Clear();
_childPackagers = null;
}
_renderer = null;
}
}
}
public void Load()
{
SetElement(null, _element);
}
void AddChild(VisualElement view, IVisualElementRenderer oldRenderer = null, RendererPool pool = null, bool sameChildren = false)
{
Performance.Start(out string reference);
if (CompressedLayout.GetIsHeadless(view))
{
var packager = new VisualElementPackager(_renderer, view);
if (_childPackagers == null)
_childPackagers = new Dictionary<BindableObject, VisualElementPackager>();
view.IsPlatformEnabled = true;
packager.Load();
_childPackagers[view] = packager;
}
else
{
if (_childViews == null)
_childViews = new List<IVisualElementRenderer>();
IVisualElementRenderer renderer = oldRenderer;
if (pool != null)
renderer = pool.GetFreeRenderer(view);
if (renderer == null || (renderer.View?.Handle ?? IntPtr.Zero) == IntPtr.Zero)
{
Performance.Start(reference, "New renderer");
renderer = Platform.CreateRenderer(view, _renderer.View.Context);
Performance.Stop(reference, "New renderer");
}
if (renderer == oldRenderer)
{
renderer.Element?.ClearValue(Platform.RendererProperty);
renderer.SetElement(view);
}
Performance.Start(reference, "Set renderer");
Platform.SetRenderer(view, renderer);
Performance.Stop(reference, "Set renderer");
Performance.Start(reference, "Add view");
if (!sameChildren)
{
(_renderer.View as ViewGroup)?.AddView(renderer.View);
_childViews.Add(renderer);
}
Performance.Stop(reference, "Add view");
}
Performance.Stop(reference);
}
void EnsureChildOrder() => EnsureChildOrder(false);
void EnsureChildOrder(bool onlyUpdateElevations)
{
float elevationToSet = 0;
for (var i = 0; i < ElementController.LogicalChildren.Count; i++)
{
Element child = ElementController.LogicalChildren[i];
var element = (VisualElement)child;
if (element != null)
{
IVisualElementRenderer r = Platform.GetRenderer(element);
if (r != null)
{
if (Forms.IsLollipopOrNewer)
{
var elevation = ElevationHelper.GetElevation(r.View) ?? 0;
var elementElevation = ElevationHelper.GetElevation(element, r.View.Context);
if (elementElevation == null)
{
if (elevation > elevationToSet)
elevationToSet = elevation;
if(r.View.Elevation != elevationToSet)
r.View.Elevation = elevationToSet;
}
}
if (!onlyUpdateElevations)
(_renderer.View as ViewGroup)?.BringChildToFront(r.View);
}
}
}
}
void OnChildAdded(object sender, ElementEventArgs e)
{
var view = e.Element as VisualElement;
if (view != null)
AddChild(view);
int itemCount = ElementController.LogicalChildren.Count;
if (itemCount <= 1)
return;
Element lastChild = ElementController.LogicalChildren[itemCount - 1];
if (lastChild != view)
{
EnsureChildOrder();
return;
}
if (!Forms.IsLollipopOrNewer)
return;
Element previousChild = ElementController.LogicalChildren[itemCount - 2];
IVisualElementRenderer lastRenderer = null;
IVisualElementRenderer previousRenderer = null;
if (lastChild is VisualElement last)
lastRenderer = Platform.GetRenderer(last);
if (previousChild is VisualElement previous)
previousRenderer = Platform.GetRenderer(previous);
if (ElevationHelper.GetElevation(lastRenderer?.View) < ElevationHelper.GetElevation(previousRenderer?.View))
EnsureChildOrder();
}
void OnChildRemoved(object sender, ElementEventArgs e)
{
Performance.Start(out string reference);
var view = e.Element as VisualElement;
if (view != null)
RemoveChild(view);
Performance.Stop(reference);
}
void OnChildrenReordered(object sender, EventArgs e)
{
EnsureChildOrder();
}
void RemoveChild(VisualElement view)
{
IVisualElementRenderer renderer = Platform.GetRenderer(view);
if (renderer == null) // child is itself a compressed layout
{
if (_childPackagers != null && _childPackagers.TryGetValue(view, out VisualElementPackager packager))
{
foreach (var child in view.LogicalChildren)
{
if (child is VisualElement ve)
packager.RemoveChild(ve);
}
}
}
else
{
_childViews.Remove(renderer);
if (renderer.View.IsAlive())
{
renderer.View.RemoveFromParent();
}
renderer.Dispose();
}
}
void SetElement(VisualElement oldElement, VisualElement newElement)
{
Performance.Start(out string reference);
var sameChildrenTypes = false;
ReadOnlyCollection<Element> newChildren = null, oldChildren = null;
RendererPool pool = null;
if (oldElement != null)
{
oldElement.ChildAdded -= _childAddedHandler;
oldElement.ChildRemoved -= _childRemovedHandler;
oldElement.ChildrenReordered -= _childReorderedHandler;
oldChildren = ((IElementController)oldElement).LogicalChildren;
if (newElement != null)
{
sameChildrenTypes = true;
newChildren = ((IElementController)newElement).LogicalChildren;
if (oldChildren.Count == newChildren.Count)
{
for (var i = 0; i < oldChildren.Count; i++)
{
if (oldChildren[i].GetType() != newChildren[i].GetType())
{
sameChildrenTypes = false;
break;
}
}
}
else
sameChildrenTypes = false;
}
else
{
for (var i = 0; i < oldChildren.Count; i++)
{
RemoveChild((VisualElement)oldChildren[i]);
}
}
if (!sameChildrenTypes)
{
_childViews = new List<IVisualElementRenderer>();
pool = new RendererPool(_renderer, oldElement);
pool.ClearChildrenRenderers();
}
}
if (newElement != null)
{
Performance.Start(reference, "Setup");
newElement.ChildAdded += _childAddedHandler;
newElement.ChildRemoved += _childRemovedHandler;
newElement.ChildrenReordered += _childReorderedHandler;
newChildren = newChildren ?? ((IElementController)newElement).LogicalChildren;
for (var i = 0; i < newChildren.Count; i++)
{
IVisualElementRenderer oldRenderer = null;
if (oldChildren != null && sameChildrenTypes && _childViews != null)
oldRenderer = _childViews[i];
AddChild((VisualElement)newChildren[i], oldRenderer, pool, sameChildrenTypes);
}
#if DEBUG
//if (renderer.Element.LogicalChildren.Any() && renderer.ViewGroup.ChildCount != renderer.Element.LogicalChildren.Count)
// throw new InvalidOperationException ("SetElement did not create the correct number of children");
#endif
EnsureChildOrder();
Performance.Stop(reference, "Setup");
}
Performance.Stop(reference);
}
}
}