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Fix FlyoutItem recycling (#13681)
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* Correctly Disable View Recycling Android Flyout

* - fix android to not reset element when items are removed

* - fix iOS to not always recreate cells
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@PureWeen
PureWeen committed Feb 9, 2021
1 parent e08748c commit 053ede6
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Showing 4 changed files with 107 additions and 26 deletions.
69 changes: 52 additions & 17 deletions Xamarin.Forms.Platform.Android/Renderers/ShellFlyoutRecyclerAdapter.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,13 +16,12 @@ public class ShellFlyoutRecyclerAdapter : RecyclerView.Adapter
readonly IShellContext _shellContext;
List<AdapterListItem> _listItems;
List<List<Element>> _flyoutGroupings;
Dictionary<int, DataTemplate> _templateMap = new Dictionary<int, DataTemplate>();
Action<Element> _selectedCallback;
bool _disposed;
ElementViewHolder _elementViewHolder;

public ShellFlyoutRecyclerAdapter(IShellContext shellContext, Action<Element> selectedCallback)
{
HasStableIds = true;
_shellContext = shellContext;

ShellController.FlyoutItemsChanged += OnFlyoutItemsChanged;
Expand All @@ -43,7 +42,22 @@ public ShellFlyoutRecyclerAdapter(IShellContext shellContext, Action<Element> se

public override int GetItemViewType(int position)
{
var item = _listItems[position];
return _listItems[position].Index;
}

DataTemplate GetDataTemplate(int viewTypeId)
{
AdapterListItem item = null;

foreach(var ali in _listItems)
{
if(viewTypeId == ali.Index)
{
item = ali;
break;
}
}

DataTemplate dataTemplate = ShellController.GetFlyoutItemDataTemplate(item.Element);
if (item.Element is IMenuItemController)
{
Expand All @@ -57,18 +71,26 @@ public override int GetItemViewType(int position)
}

var template = dataTemplate.SelectDataTemplate(item.Element, Shell);
var id = ((IDataTemplateController)template).Id;

_templateMap[id] = template;

return id;
return template;
}

public override void OnViewRecycled(Java.Lang.Object holder)
{
if (holder is ElementViewHolder evh)
{
evh.Element = null;
// only clear out the Element if the item has been removed
bool found = false;
foreach(var item in _listItems)
{
if(item.Element == evh.Element)
{
found = true;
break;
}
}

if(!found)
evh.Element = null;
}

base.OnViewRecycled(holder);
Expand Down Expand Up @@ -154,7 +176,7 @@ public override AView FocusSearch([GeneratedEnum] FocusSearchDirection direction

public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
{
var template = _templateMap[viewType];
var template = GetDataTemplate(viewType);

var content = (View)template.CreateContent();

Expand All @@ -175,14 +197,13 @@ public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int
container.LayoutParameters = new LP(LP.MatchParent, LP.WrapContent);
linearLayout.AddView(container);

_elementViewHolder = new ElementViewHolder(content, linearLayout, bar, _selectedCallback, _shellContext.Shell);

return _elementViewHolder;
return new ElementViewHolder(content, linearLayout, bar, _selectedCallback, _shellContext.Shell);
}

protected virtual List<AdapterListItem> GenerateItemList()
{
var result = new List<AdapterListItem>();
_listItems = _listItems ?? result;

List<List<Element>> grouping = ((IShellController)_shellContext.Shell).GenerateFlyoutGrouping();

Expand All @@ -198,7 +219,18 @@ protected virtual List<AdapterListItem> GenerateItemList()
bool first = !skip;
foreach (var element in sublist)
{
result.Add(new AdapterListItem(element, first));
AdapterListItem toAdd = null;
foreach (var existingItem in _listItems)
{
if(existingItem.Element == element)
{
existingItem.DrawTopLine = first;
toAdd = existingItem;
}
}

toAdd = toAdd ?? new AdapterListItem(element, first);
result.Add(toAdd);
first = false;
}
skip = false;
Expand Down Expand Up @@ -229,24 +261,27 @@ protected override void Dispose(bool disposing)
{
((IShellController)Shell).FlyoutItemsChanged -= OnFlyoutItemsChanged;

_elementViewHolder?.Dispose();

_listItems = null;
_selectedCallback = null;
_elementViewHolder = null;
}

base.Dispose(disposing);
}

public class AdapterListItem
{
// This ensures that we have a stable id for each element
// if the elements change position
static int IndexCounter = 0;

public AdapterListItem(Element element, bool drawTopLine = false)
{
DrawTopLine = drawTopLine;
Element = element;
Index = IndexCounter++;
}

public int Index { get; }
public bool DrawTopLine { get; set; }
public Element Element { get; set; }
}
Expand Down
2 changes: 1 addition & 1 deletion Xamarin.Forms.Platform.iOS/Renderers/ShellTableViewController.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,7 @@ protected ShellTableViewSource CreateShellTableViewSource()

void OnFlyoutItemsChanged(object sender, EventArgs e)
{
_source.ClearCache();
_source.ReSyncCache();
TableView.ReloadData();
ShellFlyoutContentManager.UpdateVerticalScrollMode();
}
Expand Down
39 changes: 38 additions & 1 deletion Xamarin.Forms.Platform.iOS/Renderers/ShellTableViewSource.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,41 @@ public List<List<Element>> Groups

protected virtual DataTemplate DefaultMenuItemTemplate => null;

internal void ReSyncCache()
{
var newGroups = ((IShellController)_context.Shell).GenerateFlyoutGrouping();

if (newGroups == _groups)
return;

_groups = newGroups;
if (_cells == null)
{
_cells = new Dictionary<Element, UIContainerCell>();
return;
}

var oldList = _cells;
_cells = new Dictionary<Element, UIContainerCell>();

foreach (var group in newGroups)
{
foreach(var element in group)
{
UIContainerCell result;
if(oldList.TryGetValue(element, out result))
{
_cells.Add(element, result);
oldList.Remove(element);
}
}
}

foreach (var cell in oldList.Values)
cell.Disconnect(_context.Shell);
}


public void ClearCache()
{
var newGroups = ((IShellController)_context.Shell).GenerateFlyoutGrouping();
Expand Down Expand Up @@ -125,7 +160,7 @@ public override UITableViewCell GetCell(UITableView tableView, NSIndexPath index
else
{
var view = _cells[context].View;
cell.Disconnect();
cell.Disconnect(keepRenderer: true);
cell = new UIContainerCell(cellId, view, _context.Shell, context);
}

Expand All @@ -148,8 +183,10 @@ public override nfloat GetHeightForFooter(UITableView tableView, nint section)
{
if (section < Groups.Count - 1)
return 1;

return 0;
}

public override UIView GetViewForFooter(UITableView tableView, nint section)
{
return new SeparatorView();
Expand Down
23 changes: 16 additions & 7 deletions Xamarin.Forms.Platform.iOS/Renderers/UIContainerCell.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,9 +18,14 @@ internal UIContainerCell(string cellId, View view, Shell shell, object context)
View = view;
View.MeasureInvalidated += MeasureInvalidated;
SelectionStyle = UITableViewCellSelectionStyle.None;

_renderer = Platform.CreateRenderer(view);
Platform.SetRenderer(view, _renderer);

_renderer = Platform.GetRenderer(view);

if (_renderer == null)
{
_renderer = Platform.CreateRenderer(view);
Platform.SetRenderer(view, _renderer);
}

ContentView.AddSubview(_renderer.NativeView);
_renderer.NativeView.ClipsToBounds = true;
Expand Down Expand Up @@ -49,15 +54,18 @@ internal void ReloadRow()
TableView.ReloadRows(new[] { IndexPath }, UITableViewRowAnimation.Automatic);
}

internal void Disconnect(Shell shell = null)
internal void Disconnect(Shell shell = null, bool keepRenderer = false)
{
ViewMeasureInvalidated = null;
View.MeasureInvalidated -= MeasureInvalidated;
if (_bindingContext != null && _bindingContext is BaseShellItem baseShell)
baseShell.PropertyChanged -= OnElementPropertyChanged;

_bindingContext = null;
Platform.SetRenderer(View, null);

if (!keepRenderer)
Platform.SetRenderer(View, null);

if (shell != null)
shell.RemoveLogicalChild(shell);

Expand All @@ -70,7 +78,8 @@ internal void Disconnect(Shell shell = null)
public object BindingContext
{
get => _bindingContext;
set {
set
{
if (value == _bindingContext)
return;

Expand All @@ -91,7 +100,7 @@ public object BindingContext
public override void LayoutSubviews()
{
base.LayoutSubviews();
if(View != null)
if (View != null)
View.Layout(Bounds.ToRectangle());
}

Expand Down

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