src/Tizen.NUI.Components/Controls/RecyclerView/CollectionView.cs

   1 /* Copyright (c) 2021 Samsung Electronics Co., Ltd.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at
   6  *
   7  * http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  *
  15  */
  16 using System;
  17 using System.Linq;
  18 using System.Collections;
  19 using System.Collections.Generic;
  20 using System.Collections.Specialized;
  21 using System.Windows.Input;
  22 using System.ComponentModel;
  23 using Tizen.NUI.BaseComponents;
  24 using Tizen.NUI.Binding;
  25
  26 namespace Tizen.NUI.Components
  27 {
  28     /// <summary>
  29     /// Selectable RecyclerView that presenting a collection of items with variable layouters.
  30     /// </summary>
  31     /// <since_tizen> 9 </since_tizen>
  32     public class CollectionView : RecyclerView
  33     {
  34         /// <summary>
  35         /// Binding Property of selected item in single selection.
  36         /// </summary>
  37         /// <since_tizen> 9 </since_tizen>
  38         public static readonly BindableProperty SelectedItemProperty =
  39             BindableProperty.Create(nameof(SelectedItem), typeof(object), typeof(CollectionView), null,
  40                 propertyChanged: (bindable, oldValue, newValue) =>
  41                 {
  42                     var colView = (CollectionView)bindable;
  43                     oldValue = colView.selectedItem;
  44                     colView.selectedItem = newValue;
  45                     var args = new SelectionChangedEventArgs(oldValue, newValue);
  46
  47                     foreach (RecyclerViewItem item in colView.ContentContainer.Children.Where((item) => item is RecyclerViewItem))
  48                     {
  49                         if (item.BindingContext == null) continue;
  50                         if (item.BindingContext == oldValue) item.IsSelected = false;
  51                         else if (item.BindingContext == newValue) item.IsSelected = true;
  52                     }
  53
  54                     SelectionPropertyChanged(colView, args);
  55                 },
  56                 defaultValueCreator: (bindable) =>
  57                 {
  58                     var colView = (CollectionView)bindable;
  59                     return colView.selectedItem;
  60                 });
  61
  62         /// <summary>
  63         /// Binding Property of selected items list in multiple selection.
  64         /// </summary>
  65         /// <since_tizen> 9 </since_tizen>
  66         public static readonly BindableProperty SelectedItemsProperty =
  67             BindableProperty.Create(nameof(SelectedItems), typeof(IList<object>), typeof(CollectionView), null,
  68                 propertyChanged: (bindable, oldValue, newValue) =>
  69                 {
  70                     var colView = (CollectionView)bindable;
  71                     var oldSelection = colView.selectedItems ?? selectEmpty;
  72                     //FIXME : CoerceSelectedItems calls only isCreatedByXaml
  73                     var newSelection = (SelectionList)CoerceSelectedItems(colView, newValue);
  74                     colView.selectedItems = newSelection;
  75                     colView.SelectedItemsPropertyChanged(oldSelection, newSelection);
  76                 },
  77                 defaultValueCreator: (bindable) =>
  78                 {
  79                     var colView = (CollectionView)bindable;
  80                     colView.selectedItems = colView.selectedItems ?? new SelectionList(colView);
  81                     return colView.selectedItems;
  82                 });
  83
  84         /// <summary>
  85         /// Binding Property of selected items list in multiple selection.
  86         /// </summary>
  87         /// <since_tizen> 9 </since_tizen>
  88         public static readonly BindableProperty SelectionModeProperty =
  89             BindableProperty.Create(nameof(SelectionMode), typeof(ItemSelectionMode), typeof(CollectionView), ItemSelectionMode.None,
  90                 propertyChanged: (bindable, oldValue, newValue) =>
  91                 {
  92                     var colView = (CollectionView)bindable;
  93                     oldValue = colView.selectionMode;
  94                     colView.selectionMode = (ItemSelectionMode)newValue;
  95                     SelectionModePropertyChanged(colView, oldValue, newValue);
  96                 },
  97                 defaultValueCreator: (bindable) =>
  98                 {
  99                     var colView = (CollectionView)bindable;
 100                     return colView.selectionMode;
 101                 });
 102
 103         /// <summary>
 104         /// Binding Property of items data source.
 105         /// </summary>
 106         [EditorBrowsable(EditorBrowsableState.Never)]
 107         public static readonly BindableProperty ItemsSourceProperty =
 108             BindableProperty.Create(nameof(ItemsSource), typeof(IEnumerable), typeof(CollectionView), null,
 109                 propertyChanged: (bindable, oldValue, newValue) =>
 110                 {
 111                     var colView = (CollectionView)bindable;
 112                     oldValue = colView.itemsSource;
 113
 114                     if (oldValue != null)
 115                     {
 116                         // Clearing old data!
 117                         if (oldValue is INotifyCollectionChanged prevNotifyCollectionChanged)
 118                         {
 119                             prevNotifyCollectionChanged.CollectionChanged -= colView.CollectionChanged;
 120                         }
 121                         if (colView.selectedItem != null) colView.selectedItem = null;
 122                         colView.selectedItems?.Clear();
 123                     }
 124
 125                     colView.itemsSource = (IEnumerable)newValue;
 126
 127                     if (newValue == null)
 128                     {
 129                         colView.InternalItemSource?.Dispose();
 130                         colView.InternalItemSource = null;
 131                         colView.itemsLayouter?.Clear();
 132                         colView.ClearCache();
 133                         return;
 134                     }
 135                     if (newValue is INotifyCollectionChanged newNotifyCollectionChanged)
 136                     {
 137                         newNotifyCollectionChanged.CollectionChanged += colView.CollectionChanged;
 138                     }
 139
 140                     colView.InternalItemSource?.Dispose();
 141                     colView.InternalItemSource = ItemsSourceFactory.Create(colView);
 142
 143                     if (colView.itemsLayouter == null) return;
 144
 145                     colView.needInitalizeLayouter = true;
 146                     colView.Init();
 147                 },
 148                 defaultValueCreator: (bindable) =>
 149                 {
 150                     var colView = (CollectionView)bindable;
 151                     return colView.itemsSource;
 152                 });
 153
 154
 155         private static readonly IList<object> selectEmpty = new List<object>(0);
 156         private DataTemplate itemTemplate = null;
 157         private IEnumerable itemsSource = null;
 158         private ItemsLayouter itemsLayouter = null;
 159         private DataTemplate groupHeaderTemplate;
 160         private DataTemplate groupFooterTemplate;
 161         private bool isGrouped;
 162         private bool wasRelayouted = false;
 163         private bool needInitalizeLayouter = false;
 164         private object selectedItem;
 165         private SelectionList selectedItems;
 166         private bool suppressSelectionChangeNotification;
 167         private ItemSelectionMode selectionMode = ItemSelectionMode.None;
 168         private RecyclerViewItem header;
 169         private RecyclerViewItem footer;
 170         private View focusedView;
 171         private int prevFocusedDataIndex = 0;
 172         private List<RecyclerViewItem> recycleGroupHeaderCache { get; } = new List<RecyclerViewItem>();
 173         private List<RecyclerViewItem> recycleGroupFooterCache { get; } = new List<RecyclerViewItem>();
 174         private bool delayedScrollTo;
 175         private (float position, bool anim) delayedScrollToParam;
 176
 177         private bool delayedIndexScrollTo;
 178         private (int index, bool anim, ItemScrollTo scrollTo) delayedIndexScrollToParam;
 179
 180         /// <summary>
 181         /// Base constructor.
 182         /// </summary>
 183         /// <since_tizen> 9 </since_tizen>
 184         public CollectionView() : base()
 185         {
 186             FocusGroup = true;
 187             SetKeyboardNavigationSupport(true);
 188         }
 189
 190         /// <summary>
 191         /// Base constructor with ItemsSource
 192         /// </summary>
 193         /// <param name="itemsSource">item's data source</param>
 194         /// <since_tizen> 9 </since_tizen>
 195         public CollectionView(IEnumerable itemsSource) : this()
 196         {
 197             ItemsSource = itemsSource;
 198         }
 199
 200         /// <summary>
 201         /// Base constructor with ItemsSource, ItemsLayouter and ItemTemplate
 202         /// </summary>
 203         /// <param name="itemsSource">item's data source</param>
 204         /// <param name="layouter">item's layout manager</param>
 205         /// <param name="template">item's view template with data bindings</param>
 206         [EditorBrowsable(EditorBrowsableState.Never)]
 207         public CollectionView(IEnumerable itemsSource, ItemsLayouter layouter, DataTemplate template) : this()
 208         {
 209             ItemsSource = itemsSource;
 210             ItemTemplate = template;
 211             ItemsLayouter = layouter;
 212         }
 213
 214         /// <summary>
 215         /// Event of Selection changed.
 216         /// previous selection list and current selection will be provided.
 217         /// </summary>
 218         /// <since_tizen> 9 </since_tizen>
 219         public event EventHandler<SelectionChangedEventArgs> SelectionChanged;
 220
 221         /// <summary>
 222         /// Align item in the viewport when ScrollTo() calls.
 223         /// </summary>
 224         /// <since_tizen> 9 </since_tizen>
 225         public enum ItemScrollTo
 226         {
 227             /// <summary>
 228             /// Scroll to show item in nearest viewport on scroll direction.
 229             /// item is above the scroll viewport, item will be came into front,
 230             /// item is under the scroll viewport, item will be came into end,
 231             /// item is in the scroll viewport, no scroll.
 232             /// </summary>
 233             /// <since_tizen> 9 </since_tizen>
 234             Nearest,
 235             /// <summary>
 236             /// Scroll to show item in start of the viewport.
 237             /// </summary>
 238             /// <since_tizen> 9 </since_tizen>
 239             Start,
 240             /// <summary>
 241             /// Scroll to show item in center of the viewport.
 242             /// </summary>
 243             /// <since_tizen> 9 </since_tizen>
 244             Center,
 245             /// <summary>
 246             /// Scroll to show item in end of the viewport.
 247             /// </summary>
 248             /// <since_tizen> 9 </since_tizen>
 249             End,
 250         }
 251
 252         /// <summary>
 253         /// Item's source data in IEnumerable.
 254         /// </summary>
 255         /// <since_tizen> 9 </since_tizen>
 256         public override IEnumerable ItemsSource
 257         {
 258             get => (IEnumerable)GetValue(ItemsSourceProperty);
 259             set => SetValue(ItemsSourceProperty, value);
 260         }
 261
 262         /// <summary>
 263         /// DataTemplate for items.
 264         /// Create visual contents and binding properties.
 265         /// return object type is restricted RecyclerViewItem.
 266         /// <seealso cref="Tizen.NUI.Binding.DataTemplate" />
 267         /// </summary>
 268         /// <since_tizen> 9 </since_tizen>
 269         public override DataTemplate ItemTemplate
 270         {
 271             get
 272             {
 273                 return itemTemplate;
 274             }
 275             set
 276             {
 277                 itemTemplate = value;
 278                 if (value == null)
 279                 {
 280                     return;
 281                 }
 282
 283                 needInitalizeLayouter = true;
 284                 Init();
 285             }
 286         }
 287
 288         /// <summary>
 289         /// Items Layouter.
 290         /// Layouting items on the scroll ContentContainer.
 291         /// <seealso cref="ItemsLayouter" />
 292         /// <seealso cref="LinearLayouter" />
 293         /// <seealso cref="GridLayouter" />
 294         /// </summary>
 295         /// <since_tizen> 9 </since_tizen>
 296         public virtual ItemsLayouter ItemsLayouter
 297         {
 298             get
 299             {
 300                 return itemsLayouter;
 301             }
 302             set
 303             {
 304                 itemsLayouter?.Clear();
 305                 ClearCache();
 306
 307                 itemsLayouter = value;
 308                 base.InternalItemsLayouter = itemsLayouter;
 309                 if (value == null)
 310                 {
 311                     needInitalizeLayouter = false;
 312                     return;
 313                 }
 314
 315                 needInitalizeLayouter = true;
 316
 317                 var styleName = "Tizen.NUI.Components." + (itemsLayouter is LinearLayouter? "LinearLayouter" : (itemsLayouter is GridLayouter ? "GridLayouter" : "ItemsLayouter"));
 318                 ViewStyle layouterStyle = ThemeManager.GetStyle(styleName);
 319                 if (layouterStyle != null)
 320                 {
 321                     itemsLayouter.Padding = new Extents(layouterStyle.Padding);
 322                 }
 323                 Init();
 324             }
 325         }
 326
 327         /// <summary>
 328         /// Scrolling direction to display items layout.
 329         /// </summary>
 330         /// <since_tizen> 9 </since_tizen>
 331         public new Direction ScrollingDirection
 332         {
 333             get
 334             {
 335                 return base.ScrollingDirection;
 336             }
 337             set
 338             {
 339                 if (base.ScrollingDirection != value)
 340                 {
 341                     base.ScrollingDirection = value;
 342                     needInitalizeLayouter = true;
 343                     Init();
 344                 }
 345             }
 346         }
 347
 348         /// <summary>
 349         /// Selected item in single selection.
 350         /// </summary>
 351         /// <since_tizen> 9 </since_tizen>
 352         public object SelectedItem
 353         {
 354             get => GetValue(SelectedItemProperty);
 355             set => SetValue(SelectedItemProperty, value);
 356         }
 357
 358         /// <summary>
 359         /// Selected items list in multiple selection.
 360         /// </summary>
 361         /// <since_tizen> 9 </since_tizen>
 362         public IList<object> SelectedItems
 363         {
 364             get => (IList<object>)GetValue(SelectedItemsProperty);
 365             // set => SetValue(SelectedItemsProperty, new SelectionList(this, value));
 366         }
 367
 368         /// <summary>
 369         /// Selection mode to handle items selection. See ItemSelectionMode for details.
 370         /// </summary>
 371         /// <since_tizen> 9 </since_tizen>
 372         public ItemSelectionMode SelectionMode
 373         {
 374             get => (ItemSelectionMode)GetValue(SelectionModeProperty);
 375             set => SetValue(SelectionModeProperty, value);
 376         }
 377
 378         /// <summary>
 379         /// Command of selection changed.
 380         /// </summary>
 381         [EditorBrowsable(EditorBrowsableState.Never)]
 382         public ICommand SelectionChangedCommand { set; get; }
 383
 384         /// <summary>
 385         /// Command parameter of selection changed.
 386         /// </summary>
 387         [EditorBrowsable(EditorBrowsableState.Never)]
 388         public object SelectionChangedCommandParameter { set; get; }
 389
 390         /// <summary>
 391         /// Header item placed in top-most position.
 392         /// </summary>
 393         /// <remarks>Please note that, internal index will be increased by header.</remarks>
 394         /// <since_tizen> 9 </since_tizen>
 395         public RecyclerViewItem Header
 396         {
 397             get => header;
 398             set
 399             {
 400                 if (header != null)
 401                 {
 402                     //ContentContainer.Remove(header);
 403                     Utility.Dispose(header);
 404                 }
 405                 if (value != null)
 406                 {
 407                     value.Index = 0;
 408                     value.ParentItemsView = this;
 409                     value.IsHeader = true;
 410                     ContentContainer.Add(value);
 411                 }
 412                 header = value;
 413                 if (InternalItemSource != null)
 414                 {
 415                     InternalItemSource.HasHeader = (value != null);
 416                 }
 417                 needInitalizeLayouter = true;
 418                 Init();
 419             }
 420         }
 421
 422         /// <summary>
 423         /// Footer item placed in bottom-most position.
 424         /// </summary>
 425         /// <remarks>Please note that, internal index will be increased by footer.</remarks>
 426         /// <since_tizen> 9 </since_tizen>
 427         public RecyclerViewItem Footer
 428         {
 429             get => footer;
 430             set
 431             {
 432                 if (footer != null)
 433                 {
 434                     //ContentContainer.Remove(footer);
 435                     Utility.Dispose(footer);
 436                 }
 437                 if (value != null)
 438                 {
 439                     value.Index = InternalItemSource?.Count ?? 0;
 440                     value.ParentItemsView = this;
 441                     value.IsFooter = true;
 442                     ContentContainer.Add(value);
 443                 }
 444                 footer = value;
 445                 if (InternalItemSource != null)
 446                 {
 447                     InternalItemSource.HasFooter = (value != null);
 448                 }
 449                 needInitalizeLayouter = true;
 450                 Init();
 451             }
 452         }
 453
 454         /// <summary>
 455         /// Enable groupable view.
 456         /// </summary>
 457         [EditorBrowsable(EditorBrowsableState.Never)]
 458         public bool IsGrouped
 459         {
 460             get => isGrouped;
 461             set
 462             {
 463                 isGrouped = value;
 464                 needInitalizeLayouter = true;
 465                 //Need to re-intialize Internal Item Source.
 466                 if (InternalItemSource != null)
 467                 {
 468                     InternalItemSource.Dispose();
 469                     InternalItemSource = null;
 470                 }
 471                 if (ItemsSource != null)
 472                     InternalItemSource = ItemsSourceFactory.Create(this);
 473                 Init();
 474             }
 475         }
 476
 477         /// <summary>
 478         ///  DataTemplate of group header.
 479         /// </summary>
 480         /// <remarks>Please note that, internal index will be increased by group header.
 481         /// GroupHeaderTemplate is essential for groupable view.</remarks>
 482         [EditorBrowsable(EditorBrowsableState.Never)]
 483         public DataTemplate GroupHeaderTemplate
 484         {
 485             get
 486             {
 487                 return groupHeaderTemplate;
 488             }
 489             set
 490             {
 491                 groupHeaderTemplate = value;
 492                 needInitalizeLayouter = true;
 493                 //Need to re-intialize Internal Item Source.
 494                 if (InternalItemSource != null)
 495                 {
 496                     InternalItemSource.Dispose();
 497                     InternalItemSource = null;
 498                 }
 499                 if (ItemsSource != null)
 500                     InternalItemSource = ItemsSourceFactory.Create(this);
 501                 Init();
 502             }
 503         }
 504
 505         /// <summary>
 506         /// DataTemplate of group footer. Group feature is not supported yet.
 507         /// </summary>
 508         /// <remarks>Please note that, internal index will be increased by group footer.</remarks>
 509         [EditorBrowsable(EditorBrowsableState.Never)]
 510         public DataTemplate GroupFooterTemplate
 511         {
 512             get
 513             {
 514                 return groupFooterTemplate;
 515             }
 516             set
 517             {
 518                 groupFooterTemplate = value;
 519                 needInitalizeLayouter = true;
 520                 //Need to re-intialize Internal Item Source.
 521                 if (InternalItemSource != null)
 522                 {
 523                     InternalItemSource.Dispose();
 524                     InternalItemSource = null;
 525                 }
 526                 if (ItemsSource != null)
 527                     InternalItemSource = ItemsSourceFactory.Create(this);
 528                 Init();
 529             }
 530         }
 531
 532         /// <summary>
 533         /// Internal encapsulated items data source.
 534         /// </summary>
 535         internal new IGroupableItemSource InternalItemSource
 536         {
 537             get
 538             {
 539                 return (base.InternalItemSource as IGroupableItemSource);
 540             }
 541             set
 542             {
 543                 base.InternalItemSource = value;
 544             }
 545         }
 546
 547         /// <summary>
 548         /// Size strategy of measuring scroll content. see details in ItemSizingStrategy.
 549         /// </summary>
 550         [EditorBrowsable(EditorBrowsableState.Never)]
 551         internal ItemSizingStrategy SizingStrategy { get; set; }
 552
 553         /// <inheritdoc/>
 554         /// <since_tizen> 9 </since_tizen>
 555         public override void OnRelayout(Vector2 size, RelayoutContainer container)
 556         {
 557             base.OnRelayout(size, container);
 558
 559             wasRelayouted = true;
 560             if (needInitalizeLayouter) Init();
 561         }
 562
 563         /// <inheritdoc/>
 564         [EditorBrowsable(EditorBrowsableState.Never)]
 565         public override void NotifyDataSetChanged()
 566         {
 567             if (selectedItem != null)
 568             {
 569                 selectedItem = null;
 570             }
 571             if (selectedItems != null)
 572             {
 573                 selectedItems.Clear();
 574             }
 575
 576             base.NotifyDataSetChanged();
 577         }
 578
 579         /// <inheritdoc/>
 580         [EditorBrowsable(EditorBrowsableState.Never)]
 581         public override View GetNextFocusableView(View currentFocusedView, View.FocusDirection direction, bool loopEnabled)
 582         {
 583             View nextFocusedView = null;
 584
 585             if (focusedView == null)
 586             {
 587                 // If focusedView is null, find child which has previous data index
 588                 if (ContentContainer.Children.Count > 0 && InternalItemSource.Count > 0)
 589                 {
 590                     for (int i = 0; i < ContentContainer.Children.Count; i++)
 591                     {
 592                         RecyclerViewItem item = Children[i] as RecyclerViewItem;
 593                         if (item?.Index == prevFocusedDataIndex)
 594                         {
 595                             nextFocusedView = item;
 596                             break;
 597                         }
 598                     }
 599                 }
 600             }
 601             else
 602             {
 603                 // If this is not first focus, request next focus to Layouter
 604                 nextFocusedView = ItemsLayouter.RequestNextFocusableView(currentFocusedView, direction, loopEnabled);
 605             }
 606
 607             if (nextFocusedView != null)
 608             {
 609                 // Check next focused view is inside of visible area.
 610                 // If it is not, move scroll position to make it visible.
 611                 Position scrollPosition = ContentContainer.CurrentPosition;
 612                 float targetPosition = -(ScrollingDirection == Direction.Horizontal ? scrollPosition.X : scrollPosition.Y);
 613
 614                 float left = nextFocusedView.Position.X;
 615                 float right = nextFocusedView.Position.X + nextFocusedView.Size.Width;
 616                 float top = nextFocusedView.Position.Y;
 617                 float bottom = nextFocusedView.Position.Y + nextFocusedView.Size.Height;
 618
 619                 float visibleRectangleLeft = -scrollPosition.X;
 620                 float visibleRectangleRight = -scrollPosition.X + Size.Width;
 621                 float visibleRectangleTop = -scrollPosition.Y;
 622                 float visibleRectangleBottom = -scrollPosition.Y + Size.Height;
 623
 624                 if (ScrollingDirection == Direction.Horizontal)
 625                 {
 626                     if ((direction == View.FocusDirection.Left || direction == View.FocusDirection.Up) && left < visibleRectangleLeft)
 627                     {
 628                         targetPosition = left;
 629                     }
 630                     else if ((direction == View.FocusDirection.Right || direction == View.FocusDirection.Down) && right > visibleRectangleRight)
 631                     {
 632                         targetPosition = right - Size.Width;
 633                     }
 634                 }
 635                 else
 636                 {
 637                     if ((direction == View.FocusDirection.Up || direction == View.FocusDirection.Left) && top < visibleRectangleTop)
 638                     {
 639                         targetPosition = top;
 640                     }
 641                     else if ((direction == View.FocusDirection.Down || direction == View.FocusDirection.Right) && bottom > visibleRectangleBottom)
 642                     {
 643                         targetPosition = bottom - Size.Height;
 644                     }
 645                 }
 646
 647                 focusedView = nextFocusedView;
 648                 prevFocusedDataIndex = (nextFocusedView as RecyclerViewItem)?.Index ?? -1;
 649
 650                 ScrollTo(targetPosition, true);
 651             }
 652             else
 653             {
 654                 // If nextView is null, it means that we should move focus to outside of Control.
 655                 // Return FocusableView depending on direction.
 656                 switch (direction)
 657                 {
 658                     case View.FocusDirection.Left:
 659                         {
 660                             nextFocusedView = LeftFocusableView;
 661                             break;
 662                         }
 663                     case View.FocusDirection.Right:
 664                         {
 665                             nextFocusedView = RightFocusableView;
 666                             break;
 667                         }
 668                     case View.FocusDirection.Up:
 669                         {
 670                             nextFocusedView = UpFocusableView;
 671                             break;
 672                         }
 673                     case View.FocusDirection.Down:
 674                         {
 675                             nextFocusedView = DownFocusableView;
 676                             break;
 677                         }
 678                 }
 679
 680                 if (nextFocusedView != null)
 681                 {
 682                     focusedView = null;
 683                 }
 684                 else
 685                 {
 686                     //If FocusableView doesn't exist, not move focus.
 687                     nextFocusedView = focusedView;
 688                 }
 689             }
 690
 691             return nextFocusedView;
 692         }
 693
 694         /// <summary>
 695         /// Update selected items list in multiple selection.
 696         /// </summary>
 697         /// <param name="newSelection">updated selection list by user</param>
 698         /// <since_tizen> 9 </since_tizen>
 699         public void UpdateSelectedItems(IList<object> newSelection)
 700         {
 701             var oldSelection = new List<object>(SelectedItems);
 702
 703             suppressSelectionChangeNotification = true;
 704
 705             SelectedItems.Clear();
 706
 707             if (newSelection?.Count > 0)
 708             {
 709                 for (int n = 0; n < newSelection.Count; n++)
 710                 {
 711                     SelectedItems.Add(newSelection[n]);
 712                 }
 713             }
 714
 715             suppressSelectionChangeNotification = false;
 716
 717             SelectedItemsPropertyChanged(oldSelection, newSelection);
 718         }
 719
 720         /// <summary>
 721         /// Scroll to specific position with or without animation.
 722         /// </summary>
 723         /// <param name="position">Destination.</param>
 724         /// <param name="animate">Scroll with or without animation</param>
 725         /// <since_tizen> 9 </since_tizen>
 726         public new void ScrollTo(float position, bool animate)
 727         {
 728             if (ItemsLayouter == null) throw new Exception("Item Layouter must exist.");
 729             if ((InternalItemSource == null) || needInitalizeLayouter)
 730             {
 731                 delayedScrollTo = true;
 732                 delayedScrollToParam = (position, animate);
 733                 return;
 734             }
 735
 736             base.ScrollTo(position, animate);
 737         }
 738
 739         /// <summary>
 740         /// Scrolls to the item at the specified index.
 741         /// </summary>
 742         /// <param name="index">Index of item.</param>
 743         [EditorBrowsable(EditorBrowsableState.Never)]
 744         public new void ScrollToIndex(int index)
 745         {
 746             ScrollTo(index, true, ItemScrollTo.Start);
 747         }
 748
 749         /// <summary>
 750         /// Scroll to specific item's aligned position with or without animation.
 751         /// </summary>
 752         /// <param name="index">Target item index of dataset.</param>
 753         /// <param name="animate">Boolean flag of animation.</param>
 754         /// <param name="align">Align state of item. See details in <see cref="ItemScrollTo"/>.</param>
 755         /// <since_tizen> 9 </since_tizen>
 756         public virtual void ScrollTo(int index, bool animate = false, ItemScrollTo align = ItemScrollTo.Nearest)
 757         {
 758             if (ItemsLayouter == null) throw new Exception("Item Layouter must exist.");
 759             if ((InternalItemSource == null) || needInitalizeLayouter)
 760             {
 761                 delayedIndexScrollTo = true;
 762                 delayedIndexScrollToParam = (index, animate, align);
 763                 return;
 764             }
 765             if (index < 0 || index >= InternalItemSource.Count)
 766             {
 767                 throw new Exception("index is out of boundary. index should be a value between (0, " + InternalItemSource.Count.ToString() + ").");
 768             }
 769
 770             float scrollPos, curPos, curSize, curItemSize;
 771             (float x, float y) = ItemsLayouter.GetItemPosition(index);
 772             (float width, float height) = ItemsLayouter.GetItemSize(index);
 773             if (ScrollingDirection == Direction.Horizontal)
 774             {
 775                 scrollPos = x;
 776                 curPos = ScrollPosition.X;
 777                 curSize = Size.Width;
 778                 curItemSize = width;
 779             }
 780             else
 781             {
 782                 scrollPos = y;
 783                 curPos = ScrollPosition.Y;
 784                 curSize = Size.Height;
 785                 curItemSize = height;
 786             }
 787
 788             //Console.WriteLine("[NUI] ScrollTo [{0}:{1}], curPos{2}, itemPos{3}, curSize{4}, itemSize{5}", InternalItemSource.GetPosition(item), align, curPos, scrollPos, curSize, curItemSize);
 789             switch (align)
 790             {
 791                 case ItemScrollTo.Start:
 792                     //nothing necessary.
 793                     break;
 794                 case ItemScrollTo.Center:
 795                     scrollPos = scrollPos - (curSize / 2) + (curItemSize / 2);
 796                     break;
 797                 case ItemScrollTo.End:
 798                     scrollPos = scrollPos - curSize + curItemSize;
 799                     break;
 800                 case ItemScrollTo.Nearest:
 801                     if (scrollPos < curPos - curItemSize)
 802                     {
 803                         // item is placed before the current screen. scrollTo.Top
 804                     }
 805                     else if (scrollPos >= curPos + curSize + curItemSize)
 806                     {
 807                         // item is placed after the current screen. scrollTo.End
 808                         scrollPos = scrollPos - curSize + curItemSize;
 809                     }
 810                     else
 811                     {
 812                         // item is in the scroller. ScrollTo() is ignored.
 813                         return;
 814                     }
 815                     break;
 816             }
 817
 818             //Console.WriteLine("[NUI] ScrollTo [{0}]-------------------", scrollPos);
 819             base.ScrollTo(scrollPos, animate);
 820         }
 821
 822         /// <summary>
 823         /// Apply style to CollectionView
 824         /// </summary>
 825         /// <param name="viewStyle">The style to apply.</param>
 826         [EditorBrowsable(EditorBrowsableState.Never)]
 827         public override void ApplyStyle(ViewStyle viewStyle)
 828         {
 829             base.ApplyStyle(viewStyle);
 830             if (viewStyle != null)
 831             {
 832                 //Extension = RecyclerViewItemStyle.CreateExtension();
 833             }
 834             if (itemsLayouter != null)
 835             {
 836                 string styleName = "Tizen.NUI.Compoenents." + (itemsLayouter is LinearLayouter? "LinearLayouter" : (itemsLayouter is GridLayouter ? "GridLayouter" : "ItemsLayouter"));
 837                 ViewStyle layouterStyle = ThemeManager.GetStyle(styleName);
 838                 if (layouterStyle != null)
 839                     itemsLayouter.Padding = new Extents(layouterStyle.Padding);
 840             }
 841         }
 842
 843
 844         /// <summary>
 845         /// Scroll to specified item
 846         /// </summary>
 847         /// <remarks>
 848         /// Make sure that the item that is about to receive the accessibility highlight is visible.
 849         /// </remarks>
 850         [EditorBrowsable(EditorBrowsableState.Never)]
 851         protected override bool AccessibilityScrollToChild(View child)
 852         {
 853             foreach (RecyclerViewItem item in ContentContainer.Children.Where((item) => item is RecyclerViewItem))
 854             {
 855                 if (child == item)
 856                 {
 857                     ScrollToIndex(item.Index);
 858                     return true;
 859                 }
 860             }
 861
 862             return false;
 863         }
 864
 865         // Realize and Decorate the item.
 866         internal override RecyclerViewItem RealizeItem(int index)
 867         {
 868             RecyclerViewItem item;
 869             if (index == 0 && Header != null)
 870             {
 871                 Header.Show();
 872                 return Header;
 873             }
 874
 875             if (index == InternalItemSource.Count - 1 && Footer != null)
 876             {
 877                 Footer.Show();
 878                 return Footer;
 879             }
 880
 881             if (isGrouped)
 882             {
 883                 var context = InternalItemSource.GetItem(index);
 884                 if (InternalItemSource.IsGroupHeader(index))
 885                 {
 886                     DataTemplate templ = (groupHeaderTemplate as DataTemplateSelector)?.SelectDataTemplate(context, this) ?? groupHeaderTemplate;
 887
 888                     RecyclerViewItem groupHeader = PopRecycleGroupCache(templ, true);
 889                     if (groupHeader == null)
 890                     {
 891                         groupHeader = (RecyclerViewItem)DataTemplateExtensions.CreateContent(groupHeaderTemplate, context, this);
 892
 893                         groupHeader.Template = templ;
 894                         groupHeader.isGroupHeader = true;
 895                         groupHeader.isGroupFooter = false;
 896                         ContentContainer.Add(groupHeader);
 897                     }
 898
 899                     if (groupHeader != null)
 900                     {
 901                         groupHeader.ParentItemsView = this;
 902                         groupHeader.Index = index;
 903                         groupHeader.ParentGroup = context;
 904                         groupHeader.BindingContext = context;
 905                     }
 906                     //group selection?
 907                     item = groupHeader;
 908                 }
 909                 else if (InternalItemSource.IsGroupFooter(index))
 910                 {
 911                     DataTemplate templ = (groupFooterTemplate as DataTemplateSelector)?.SelectDataTemplate(context, this) ?? groupFooterTemplate;
 912
 913                     RecyclerViewItem groupFooter = PopRecycleGroupCache(templ, false);
 914                     if (groupFooter == null)
 915                     {
 916                         groupFooter = (RecyclerViewItem)DataTemplateExtensions.CreateContent(groupFooterTemplate, context, this);
 917
 918                         groupFooter.Template = templ;
 919                         groupFooter.isGroupHeader = false;
 920                         groupFooter.isGroupFooter = true;
 921                         ContentContainer.Add(groupFooter);
 922                     }
 923
 924                     if (groupFooter != null)
 925                     {
 926                         groupFooter.ParentItemsView = this;
 927                         groupFooter.Index = index;
 928                         groupFooter.ParentGroup = context;
 929                         groupFooter.BindingContext = context;
 930                     }
 931                     //group selection?
 932                     item = groupFooter;
 933                 }
 934                 else
 935                 {
 936                     item = base.RealizeItem(index);
 937                     item.ParentGroup = InternalItemSource.GetGroupParent(index);
 938                 }
 939             }
 940             else
 941             {
 942                 item = base.RealizeItem(index);
 943             }
 944
 945             switch (SelectionMode)
 946             {
 947                 case ItemSelectionMode.Single:
 948                 case ItemSelectionMode.SingleAlways:
 949                     if (item.BindingContext != null && item.BindingContext == SelectedItem)
 950                     {
 951                         item.IsSelected = true;
 952                     }
 953                     break;
 954
 955                 case ItemSelectionMode.Multiple:
 956                     if ((item.BindingContext != null) && (SelectedItems?.Contains(item.BindingContext) ?? false))
 957                     {
 958                         item.IsSelected = true;
 959                     }
 960                     break;
 961                 case ItemSelectionMode.None:
 962                     item.IsSelectable = false;
 963                     break;
 964             }
 965             return item;
 966         }
 967
 968         // Unrealize and caching the item.
 969         internal override void UnrealizeItem(RecyclerViewItem item, bool recycle = true)
 970         {
 971             if (item == null) return;
 972             if (item == Header)
 973             {
 974                 item?.Hide();
 975                 return;
 976             }
 977             if (item == Footer)
 978             {
 979                 item.Hide();
 980                 return;
 981             }
 982             if (item.isGroupHeader || item.isGroupFooter)
 983             {
 984                 item.Index = -1;
 985                 item.ParentItemsView = null;
 986                 item.BindingContext = null;
 987                 item.IsPressed = false;
 988                 item.IsSelected = false;
 989                 item.IsEnabled = true;
 990                 item.UpdateState();
 991                 //item.Relayout -= OnItemRelayout;
 992                 if (!recycle || !PushRecycleGroupCache(item))
 993                     Utility.Dispose(item);
 994                 return;
 995             }
 996
 997             base.UnrealizeItem(item, recycle);
 998         }
 999
1000         internal void SelectedItemsPropertyChanged(IList<object> oldSelection, IList<object> newSelection)
1001         {
1002             if (suppressSelectionChangeNotification)
1003             {
1004                 return;
1005             }
1006
1007             foreach (RecyclerViewItem item in ContentContainer.Children.Where((item) => item is RecyclerViewItem))
1008             {
1009                 if (item.BindingContext == null) continue;
1010                 if (newSelection.Contains(item.BindingContext))
1011                 {
1012                     if (!item.IsSelected) item.IsSelected = true;
1013                 }
1014                 else
1015                 {
1016                     if (item.IsSelected) item.IsSelected = false;
1017                 }
1018             }
1019             SelectionPropertyChanged(this, new SelectionChangedEventArgs(oldSelection, newSelection));
1020
1021             OnPropertyChanged(SelectedItemsProperty.PropertyName);
1022         }
1023
1024         /// <summary>
1025         /// Internal selection callback.
1026         /// </summary>
1027         /// <since_tizen> 9 </since_tizen>
1028         protected virtual void OnSelectionChanged(SelectionChangedEventArgs args)
1029         {
1030             //Selection Callback
1031         }
1032
1033         /// <summary>
1034         /// Adjust scrolling position by own scrolling rules.
1035         /// Override this function when developer wants to change destination of flicking.(e.g. always snap to center of item)
1036         /// </summary>
1037         /// <param name="position">Scroll position which is calculated by ScrollableBase</param>
1038         /// <returns>Adjusted scroll destination</returns>
1039         [EditorBrowsable(EditorBrowsableState.Never)]
1040         protected override float AdjustTargetPositionOfScrollAnimation(float position)
1041         {
1042             // Destination is depending on implementation of layout manager.
1043             // Get destination from layout manager.
1044             return ItemsLayouter?.CalculateCandidateScrollPosition(position) ?? position;
1045         }
1046
1047         /// <inheritdoc/>
1048         [EditorBrowsable(EditorBrowsableState.Never)]
1049         protected override void ClearCache()
1050         {
1051             foreach (RecyclerViewItem item in recycleGroupHeaderCache)
1052             {
1053                 Utility.Dispose(item);
1054             }
1055             recycleGroupHeaderCache.Clear();
1056             foreach (RecyclerViewItem item in recycleGroupFooterCache)
1057             {
1058                 Utility.Dispose(item);
1059             }
1060             recycleGroupFooterCache.Clear();
1061             base.ClearCache();
1062         }
1063
1064
1065         /// <summary>
1066         /// OnScroll event callback. Requesting layout to the layouter with given scrollPosition.
1067         /// </summary>
1068         /// <param name="source">Scroll source object</param>
1069         /// <param name="args">Scroll event argument</param>
1070         /// <since_tizen> 9 </since_tizen>
1071         protected override void OnScrolling(object source, ScrollEventArgs args)
1072         {
1073             if (disposed) return;
1074
1075             if (needInitalizeLayouter && (ItemsLayouter != null))
1076             {
1077                 ItemsLayouter.Initialize(this);
1078                 needInitalizeLayouter = false;
1079             }
1080
1081             base.OnScrolling(source, args);
1082         }
1083
1084         /// <summary>
1085         /// Dispose ItemsView and all children on it.
1086         /// </summary>
1087         /// <param name="type">Dispose type.</param>
1088         /// <since_tizen> 9 </since_tizen>
1089         protected override void Dispose(DisposeTypes type)
1090         {
1091             if (disposed)
1092             {
1093                 return;
1094             }
1095
1096             if (type == DisposeTypes.Explicit)
1097             {
1098                 // From now on, no need to use this properties,
1099                 // so remove reference, to push it into garbage collector.
1100
1101                 // Arugable to disposing user-created members.
1102                 /*
1103                 if (Header != null)
1104                 {
1105                     Utility.Dispose(Header);
1106                     Header = null;
1107                 }
1108                 if (Footer != null)
1109                 {
1110                     Utility.Dispose(Footer);
1111                     Footer = null;
1112                 }
1113                 */
1114
1115                 groupHeaderTemplate = null;
1116                 groupFooterTemplate = null;
1117
1118                 if (selectedItem != null)
1119                 {
1120                     selectedItem = null;
1121                 }
1122                 if (selectedItems != null)
1123                 {
1124                     selectedItems.Clear();
1125                     selectedItems = null;
1126                 }
1127                 if (InternalItemSource != null)
1128                 {
1129                     InternalItemSource.Dispose();
1130                     InternalItemSource = null;
1131                 }
1132             }
1133
1134             base.Dispose(type);
1135         }
1136
1137         private static void SelectionPropertyChanged(CollectionView colView, SelectionChangedEventArgs args)
1138         {
1139             var command = colView.SelectionChangedCommand;
1140
1141             if (command != null)
1142             {
1143                 var commandParameter = colView.SelectionChangedCommandParameter;
1144
1145                 if (command.CanExecute(commandParameter))
1146                 {
1147                     command.Execute(commandParameter);
1148                 }
1149             }
1150             colView.SelectionChanged?.Invoke(colView, args);
1151             colView.OnSelectionChanged(args);
1152         }
1153
1154         private static object CoerceSelectedItems(BindableObject bindable, object value)
1155         {
1156             if (value == null)
1157             {
1158                 return new SelectionList((CollectionView)bindable);
1159             }
1160
1161             if (value is SelectionList)
1162             {
1163                 return value;
1164             }
1165
1166             return new SelectionList((CollectionView)bindable, value as IList<object>);
1167         }
1168
1169         private static void SelectionModePropertyChanged(BindableObject bindable, object oldValue, object newValue)
1170         {
1171             var colView = (CollectionView)bindable;
1172
1173             var oldMode = (ItemSelectionMode)oldValue;
1174             var newMode = (ItemSelectionMode)newValue;
1175
1176             IList<object> previousSelection = new List<object>();
1177             IList<object> newSelection = new List<object>();
1178
1179             switch (oldMode)
1180             {
1181                 case ItemSelectionMode.None:
1182                     break;
1183                 case ItemSelectionMode.Single:
1184                     if (colView.SelectedItem != null)
1185                     {
1186                         previousSelection.Add(colView.SelectedItem);
1187                     }
1188                     break;
1189                 case ItemSelectionMode.Multiple:
1190                     previousSelection = colView.SelectedItems;
1191                     break;
1192             }
1193
1194             switch (newMode)
1195             {
1196                 case ItemSelectionMode.None:
1197                     break;
1198                 case ItemSelectionMode.Single:
1199                     if (colView.SelectedItem != null)
1200                     {
1201                         newSelection.Add(colView.SelectedItem);
1202                     }
1203                     break;
1204                 case ItemSelectionMode.Multiple:
1205                     newSelection = colView.SelectedItems;
1206                     break;
1207             }
1208
1209             if (previousSelection.Count == newSelection.Count)
1210             {
1211                 if (previousSelection.Count == 0 || (previousSelection[0] == newSelection[0]))
1212                 {
1213                     // Both selections are empty or have the same single item; no reason to signal a change
1214                     return;
1215                 }
1216             }
1217
1218             var args = new SelectionChangedEventArgs(previousSelection, newSelection);
1219             SelectionPropertyChanged(colView, args);
1220         }
1221
1222         private void Init()
1223         {
1224             if (ItemsSource == null) return;
1225             if (ItemsLayouter == null) return;
1226             if (ItemTemplate == null) return;
1227
1228             if (disposed) return;
1229             if (needInitalizeLayouter)
1230             {
1231                 if (InternalItemSource == null) return;
1232
1233                 InternalItemSource.HasHeader = (header != null);
1234                 InternalItemSource.HasFooter = (footer != null);
1235             }
1236
1237             if (!wasRelayouted) return;
1238
1239             if (needInitalizeLayouter)
1240             {
1241                 itemsLayouter.Clear();
1242                 ClearCache();
1243
1244                 ItemsLayouter.Initialize(this);
1245                 needInitalizeLayouter = false;
1246             }
1247             ItemsLayouter.RequestLayout(0.0f, true);
1248
1249             if (delayedScrollTo)
1250             {
1251                 delayedScrollTo = false;
1252                 ScrollTo(delayedScrollToParam.position, delayedScrollToParam.anim);
1253             }
1254
1255             if (delayedIndexScrollTo)
1256             {
1257                 delayedIndexScrollTo = false;
1258                 ScrollTo(delayedIndexScrollToParam.index, delayedIndexScrollToParam.anim, delayedIndexScrollToParam.scrollTo);
1259             }
1260
1261             if (ScrollingDirection == Direction.Horizontal)
1262             {
1263                 ContentContainer.SizeWidth = ItemsLayouter.CalculateLayoutOrientationSize();
1264             }
1265             else
1266             {
1267                 ContentContainer.SizeHeight = ItemsLayouter.CalculateLayoutOrientationSize();
1268             }
1269         }
1270
1271         private bool PushRecycleGroupCache(RecyclerViewItem item)
1272         {
1273             if (item == null) throw new ArgumentNullException(nameof(item));
1274             if (RecycleCache.Count >= 20) return false;
1275             if (item.Template == null) return false;
1276             if (item.isGroupHeader)
1277             {
1278                 recycleGroupHeaderCache.Add(item);
1279             }
1280             else if (item.isGroupFooter)
1281             {
1282                 recycleGroupFooterCache.Add(item);
1283             }
1284             else return false;
1285             item.Hide();
1286             item.Index = -1;
1287             return true;
1288         }
1289
1290         private RecyclerViewItem PopRecycleGroupCache(DataTemplate Template, bool isHeader)
1291         {
1292             RecyclerViewItem viewItem = null;
1293
1294             var Cache = (isHeader ? recycleGroupHeaderCache : recycleGroupFooterCache);
1295             for (int i = 0; i < Cache.Count; i++)
1296             {
1297                 viewItem = Cache[i];
1298                 if (Template == viewItem.Template) break;
1299             }
1300
1301             if (viewItem != null)
1302             {
1303                 Cache.Remove(viewItem);
1304                 viewItem.Show();
1305             }
1306             return viewItem;
1307         }
1308         private void CollectionChanged(object sender, NotifyCollectionChangedEventArgs args)
1309         {
1310             switch (args.Action)
1311             {
1312                 case NotifyCollectionChangedAction.Add:
1313                     break;
1314                 case NotifyCollectionChangedAction.Remove:
1315                     // Clear removed items.
1316                     if (args.OldItems != null)
1317                     {
1318                         if (args.OldItems.Contains(selectedItem))
1319                         {
1320                             selectedItem = null;
1321                         }
1322
1323                         if (selectedItems != null)
1324                         {
1325                             foreach (object removed in args.OldItems)
1326                             {
1327                                 if (selectedItems.Contains(removed))
1328                                 {
1329                                     selectedItems.Remove(removed);
1330                                 }
1331                             }
1332                         }
1333                     }
1334                     break;
1335                 case NotifyCollectionChangedAction.Replace:
1336                     break;
1337                 case NotifyCollectionChangedAction.Move:
1338                     break;
1339                 case NotifyCollectionChangedAction.Reset:
1340                     break;
1341                 default:
1342                     throw new ArgumentOutOfRangeException(nameof(args));
1343             }
1344         }
1345
1346     }
1347 }