src/Tizen.NUI.Components/Controls/ScrollableBase.cs

   1 /* Copyright (c) 2020 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 Tizen.NUI.BaseComponents;
  18 using System.ComponentModel;
  19 using System.Diagnostics;
  20
  21 namespace Tizen.NUI.Components
  22 {
  23     /// <summary>
  24     /// [Draft] This class provides a View that can scroll a single View with a layout. This View can be a nest of Views.
  25     /// </summary>
  26     /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
  27     [EditorBrowsable(EditorBrowsableState.Never)]
  28     public class ScrollableBase : Control
  29     {
  30         static bool LayoutDebugScrollableBase = false; // Debug flag
  31         private Direction mScrollingDirection = Direction.Vertical;
  32         private bool mScrollEnabled = true;
  33         private int mPageWidth = 0;
  34
  35         private class ScrollableBaseCustomLayout : LayoutGroup
  36         {
  37             protected override void OnMeasure(MeasureSpecification widthMeasureSpec, MeasureSpecification heightMeasureSpec)
  38             {
  39                 Extents padding = Padding;
  40                 float totalHeight = padding.Top + padding.Bottom;
  41                 float totalWidth = padding.Start + padding.End;
  42
  43                 MeasuredSize.StateType childWidthState = MeasuredSize.StateType.MeasuredSizeOK;
  44                 MeasuredSize.StateType childHeightState = MeasuredSize.StateType.MeasuredSizeOK;
  45
  46                 Direction scrollingDirection = Direction.Vertical;
  47                 ScrollableBase scrollableBase = this.Owner as ScrollableBase;
  48                 if (scrollableBase)
  49                 {
  50                     scrollingDirection = scrollableBase.ScrollingDirection;
  51                 }
  52
  53                 // measure child, should be a single scrolling child
  54                 foreach (LayoutItem childLayout in LayoutChildren)
  55                 {
  56                     if (childLayout != null)
  57                     {
  58                         // Get size of child
  59                         // Use an Unspecified MeasureSpecification mode so scrolling child is not restricted to it's parents size in Height (for vertical scrolling)
  60                         // or Width for horizontal scrolling
  61                         MeasureSpecification unrestrictedMeasureSpec = new MeasureSpecification(heightMeasureSpec.Size, MeasureSpecification.ModeType.Unspecified);
  62
  63                         if (scrollingDirection == Direction.Vertical)
  64                         {
  65                             MeasureChildWithMargins(childLayout, widthMeasureSpec, new LayoutLength(0), unrestrictedMeasureSpec, new LayoutLength(0));  // Height unrestricted by parent
  66                         }
  67                         else
  68                         {
  69                             MeasureChildWithMargins(childLayout, unrestrictedMeasureSpec, new LayoutLength(0), heightMeasureSpec, new LayoutLength(0));  // Width unrestricted by parent
  70                         }
  71
  72                         float childWidth = childLayout.MeasuredWidth.Size.AsDecimal();
  73                         float childHeight = childLayout.MeasuredHeight.Size.AsDecimal();
  74
  75                         // Determine the width and height needed by the children using their given position and size.
  76                         // Children could overlap so find the left most and right most child.
  77                         Position2D childPosition = childLayout.Owner.Position2D;
  78                         float childLeft = childPosition.X;
  79                         float childTop = childPosition.Y;
  80
  81                         // Store current width and height needed to contain all children.
  82                         Extents childMargin = childLayout.Margin;
  83                         totalWidth = childWidth + childMargin.Start + childMargin.End;
  84                         totalHeight = childHeight + childMargin.Top + childMargin.Bottom;
  85
  86                         if (childLayout.MeasuredWidth.State == MeasuredSize.StateType.MeasuredSizeTooSmall)
  87                         {
  88                             childWidthState = MeasuredSize.StateType.MeasuredSizeTooSmall;
  89                         }
  90                         if (childLayout.MeasuredWidth.State == MeasuredSize.StateType.MeasuredSizeTooSmall)
  91                         {
  92                             childHeightState = MeasuredSize.StateType.MeasuredSizeTooSmall;
  93                         }
  94                     }
  95                 }
  96
  97
  98                 MeasuredSize widthSizeAndState = ResolveSizeAndState(new LayoutLength(totalWidth + Padding.Start + Padding.End), widthMeasureSpec, MeasuredSize.StateType.MeasuredSizeOK);
  99                 MeasuredSize heightSizeAndState = ResolveSizeAndState(new LayoutLength(totalHeight + Padding.Top + Padding.Bottom), heightMeasureSpec, MeasuredSize.StateType.MeasuredSizeOK);
 100                 totalWidth = widthSizeAndState.Size.AsDecimal();
 101                 totalHeight = heightSizeAndState.Size.AsDecimal();
 102
 103                 // Ensure layout respects it's given minimum size
 104                 totalWidth = Math.Max(totalWidth, SuggestedMinimumWidth.AsDecimal());
 105                 totalHeight = Math.Max(totalHeight, SuggestedMinimumHeight.AsDecimal());
 106
 107                 widthSizeAndState.State = childWidthState;
 108                 heightSizeAndState.State = childHeightState;
 109
 110                 SetMeasuredDimensions(ResolveSizeAndState(new LayoutLength(totalWidth + Padding.Start + Padding.End), widthMeasureSpec, childWidthState),
 111                                        ResolveSizeAndState(new LayoutLength(totalHeight + Padding.Top + Padding.Bottom), heightMeasureSpec, childHeightState));
 112
 113                 // Size of ScrollableBase is changed. Change Page width too.
 114                 scrollableBase.mPageWidth = (int)MeasuredWidth.Size.AsRoundedValue();
 115             }
 116
 117             protected override void OnLayout(bool changed, LayoutLength left, LayoutLength top, LayoutLength right, LayoutLength bottom)
 118             {
 119                 foreach (LayoutItem childLayout in LayoutChildren)
 120                 {
 121                     if (childLayout != null)
 122                     {
 123                         LayoutLength childWidth = childLayout.MeasuredWidth.Size;
 124                         LayoutLength childHeight = childLayout.MeasuredHeight.Size;
 125
 126                         Position2D childPosition = childLayout.Owner.Position2D;
 127                         Extents padding = Padding;
 128                         Extents childMargin = childLayout.Margin;
 129
 130                         LayoutLength childLeft = new LayoutLength(childPosition.X + childMargin.Start + padding.Start);
 131                         LayoutLength childTop = new LayoutLength(childPosition.Y + childMargin.Top + padding.Top);
 132
 133                         childLayout.Layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight);
 134                     }
 135                 }
 136             }
 137         } //  ScrollableBaseCustomLayout
 138
 139         /// <summary>
 140         /// The direction axis to scroll.
 141         /// </summary>
 142         /// <since_tizen> 6 </since_tizen>
 143         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
 144         [EditorBrowsable(EditorBrowsableState.Never)]
 145         public enum Direction
 146         {
 147             /// <summary>
 148             /// Horizontal axis.
 149             /// </summary>
 150             /// <since_tizen> 6 </since_tizen>
 151             Horizontal,
 152
 153             /// <summary>
 154             /// Vertical axis.
 155             /// </summary>
 156             /// <since_tizen> 6 </since_tizen>
 157             Vertical
 158         }
 159
 160         /// <summary>
 161         /// [Draft] Configurable speed threshold that register the gestures as a flick.
 162         /// If the flick speed less than the threshold then will not be considered a flick.
 163         /// </summary>
 164         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
 165         [EditorBrowsable(EditorBrowsableState.Never)]
 166         public float FlickThreshold { get; set; } = 0.2f;
 167
 168         /// <summary>
 169         /// [Draft] Configurable duration modifer for the flick animation.
 170         /// Determines the speed of the scroll, large value results in a longer flick animation. Range (0.1 - 1.0)
 171         /// </summary>
 172         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 173         [EditorBrowsable(EditorBrowsableState.Never)]
 174         public float FlickAnimationSpeed { get; set; } = 0.4f;
 175
 176         /// <summary>
 177         /// [Draft] Configurable modifer for the distance to be scrolled when flicked detected.
 178         /// It a ratio of the ScrollableBase's length. (not child's length).
 179         /// First value is the ratio of the distance to scroll with the weakest flick.
 180         /// Second value is the ratio of the distance to scroll with the strongest flick.
 181         /// Second > First.
 182         /// </summary>
 183         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 184         [EditorBrowsable(EditorBrowsableState.Never)]
 185         public Vector2 FlickDistanceMultiplierRange { get; set; } = new Vector2(0.6f, 1.8f);
 186
 187         /// <summary>
 188         /// [Draft] Scrolling direction mode.
 189         /// Default is Vertical scrolling.
 190         /// </summary>
 191         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 192         [EditorBrowsable(EditorBrowsableState.Never)]
 193         public Direction ScrollingDirection
 194         {
 195             get
 196             {
 197                 return mScrollingDirection;
 198             }
 199             set
 200             {
 201                 if (value != mScrollingDirection)
 202                 {
 203                     mScrollingDirection = value;
 204                     mPanGestureDetector.RemoveDirection(value == Direction.Horizontal ? PanGestureDetector.DirectionVertical : PanGestureDetector.DirectionHorizontal);
 205                     mPanGestureDetector.AddDirection(value == Direction.Horizontal ? PanGestureDetector.DirectionHorizontal : PanGestureDetector.DirectionVertical);
 206                 }
 207             }
 208         }
 209
 210         /// <summary>
 211         /// [Draft] Enable or disable scrolling.
 212         /// </summary>
 213         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 214         [EditorBrowsable(EditorBrowsableState.Never)]
 215         public bool ScrollEnabled
 216         {
 217             get
 218             {
 219                 return mScrollEnabled;
 220             }
 221             set
 222             {
 223                 if (value != mScrollEnabled)
 224                 {
 225                     mScrollEnabled = value;
 226                     if (mScrollEnabled)
 227                     {
 228                         mPanGestureDetector.Detected += OnPanGestureDetected;
 229                         mTapGestureDetector.Detected += OnTapGestureDetected;
 230                     }
 231                     else
 232                     {
 233                         mPanGestureDetector.Detected -= OnPanGestureDetected;
 234                         mTapGestureDetector.Detected -= OnTapGestureDetected;
 235                     }
 236                 }
 237             }
 238         }
 239
 240         /// <summary>
 241         /// [Draft] Pages mode, enables moving to the next or return to current page depending on pan displacement.
 242         /// Default is false.
 243         /// </summary>
 244         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 245         [EditorBrowsable(EditorBrowsableState.Never)]
 246         public bool SnapToPage { set; get; } = false;
 247
 248         /// <summary>
 249         /// [Draft] Get current page.
 250         /// Working propery with SnapToPage property.
 251         /// </summary>
 252         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 253         [EditorBrowsable(EditorBrowsableState.Never)]
 254         public int CurrentPage { get; private set; } = 0;
 255
 256         /// <summary>
 257         /// [Draft] Duration of scroll animation.
 258         /// </summary>
 259         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 260         [EditorBrowsable(EditorBrowsableState.Never)]
 261
 262         public int ScrollDuration { set; get; } = 125;
 263         /// <summary>
 264         /// [Draft] Scroll Available area.
 265         /// </summary>
 266         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 267         [EditorBrowsable(EditorBrowsableState.Never)]
 268         public Vector2 ScrollAvailableArea { set; get; }
 269
 270         /// <summary>
 271         /// ScrollEventArgs is a class to record scroll event arguments which will sent to user.
 272         /// </summary>
 273         /// <since_tizen> 6 </since_tizen>
 274         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 275         [EditorBrowsable(EditorBrowsableState.Never)]
 276         public class ScrollEventArgs : EventArgs
 277         {
 278             Position position;
 279
 280             /// <summary>
 281             /// Default constructor.
 282             /// </summary>
 283             /// <param name="position">Current scroll position</param>
 284             /// <since_tizen> 6 </since_tizen>
 285             /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 286             public ScrollEventArgs(Position position)
 287             {
 288                 this.position = position;
 289             }
 290
 291             /// <summary>
 292             /// [Draft] Current scroll position.
 293             /// </summary>
 294             /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 295             [EditorBrowsable(EditorBrowsableState.Never)]
 296             public Position Position
 297             {
 298                 get
 299                 {
 300                     return position;
 301                 }
 302             }
 303         }
 304
 305         /// <summary>
 306         /// An event emitted when user starts dragging ScrollableBase, user can subscribe or unsubscribe to this event handler.<br />
 307         /// </summary>
 308         /// <since_tizen> 6 </since_tizen>
 309         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 310         [EditorBrowsable(EditorBrowsableState.Never)]
 311         public event EventHandler<ScrollEventArgs> ScrollDragStartEvent;
 312
 313         /// <summary>
 314         /// An event emitted when user stops dragging ScrollableBase, user can subscribe or unsubscribe to this event handler.<br />
 315         /// </summary>
 316         /// <since_tizen> 6 </since_tizen>
 317         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 318         [EditorBrowsable(EditorBrowsableState.Never)]
 319         public event EventHandler<ScrollEventArgs> ScrollDragEndEvent;
 320
 321
 322         /// <summary>
 323         /// An event emitted when the scrolling slide animation starts, user can subscribe or unsubscribe to this event handler.<br />
 324         /// </summary>
 325         /// <since_tizen> 6 </since_tizen>
 326         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 327         [EditorBrowsable(EditorBrowsableState.Never)]
 328         public event EventHandler<ScrollEventArgs> ScrollAnimationStartEvent;
 329
 330         /// <summary>
 331         /// An event emitted when the scrolling slide animation ends, user can subscribe or unsubscribe to this event handler.<br />
 332         /// </summary>
 333         /// <since_tizen> 6 </since_tizen>
 334         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 335         [EditorBrowsable(EditorBrowsableState.Never)]
 336         public event EventHandler<ScrollEventArgs> ScrollAnimationEndEvent;
 337
 338
 339         /// <summary>
 340         /// An event emitted when scrolling, user can subscribe or unsubscribe to this event handler.<br />
 341         /// </summary>
 342         /// <since_tizen> 6 </since_tizen>
 343         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 344         [EditorBrowsable(EditorBrowsableState.Never)]
 345         public event EventHandler<ScrollEventArgs> ScrollEvent;
 346
 347         private Animation scrollAnimation;
 348         private float maxScrollDistance;
 349         private float childTargetPosition = 0.0f;
 350         private PanGestureDetector mPanGestureDetector;
 351         private TapGestureDetector mTapGestureDetector;
 352         private View mScrollingChild;
 353         private View mInterruptTouchingChild;
 354         private float multiplier = 1.0f;
 355         private bool scrolling = false;
 356         private float ratioOfScreenWidthToCompleteScroll = 0.5f;
 357         private float totalDisplacementForPan = 0.0f;
 358
 359         // If false then can only flick pages when the current animation/scroll as ended.
 360         private bool flickWhenAnimating = false;
 361         private PropertyNotification propertyNotification;
 362
 363         // Let's consider more whether this needs to be set as protected.
 364         private float finalTargetPosition;
 365
 366         /// <summary>
 367         /// [Draft] Constructor
 368         /// </summary>
 369         /// <since_tizen> 6 </since_tizen>
 370         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 371         [EditorBrowsable(EditorBrowsableState.Never)]
 372         public ScrollableBase() : base()
 373         {
 374             mPanGestureDetector = new PanGestureDetector();
 375             mPanGestureDetector.Attach(this);
 376             mPanGestureDetector.AddDirection(PanGestureDetector.DirectionVertical);
 377             mPanGestureDetector.Detected += OnPanGestureDetected;
 378
 379             mTapGestureDetector = new TapGestureDetector();
 380             mTapGestureDetector.Attach(this);
 381             mTapGestureDetector.Detected += OnTapGestureDetected;
 382
 383             ClippingMode = ClippingModeType.ClipChildren;
 384
 385             mScrollingChild = new View();
 386             mScrollingChild.Name = "DefaultScrollingChild";
 387
 388             //Interrupt touching when panning is started;
 389             mInterruptTouchingChild = new View()
 390             {
 391                 Name = "InterruptTouchingChild",
 392                 Size = new Size(Window.Instance.WindowSize),
 393                 BackgroundColor = Color.Transparent,
 394             };
 395
 396             mInterruptTouchingChild.TouchEvent += OnIterruptTouchingChildTouched;
 397
 398             Layout = new ScrollableBaseCustomLayout();
 399         }
 400
 401         private bool OnIterruptTouchingChildTouched(object source, View.TouchEventArgs args)
 402         {
 403             return true;
 404         }
 405
 406         private void OnPropertyChanged(object source, PropertyNotification.NotifyEventArgs args)
 407         {
 408             OnScroll();
 409         }
 410
 411         /// <summary>
 412         /// Called after a child has been added to the owning view.
 413         /// </summary>
 414         /// <param name="view">The child which has been added.</param>
 415         /// <since_tizen> 6 </since_tizen>
 416         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 417         [EditorBrowsable(EditorBrowsableState.Never)]
 418         public override void OnChildAdd(View view)
 419         {
 420             if (view.Name != "InterruptTouchingChild")
 421             {
 422                 if (mScrollingChild.Name != "DefaultScrollingChild")
 423                 {
 424                     propertyNotification.Notified -= OnPropertyChanged;
 425                     mScrollingChild.RemovePropertyNotification(propertyNotification);
 426                     mScrollingChild.Relayout -= OnScrollingChildRelayout;
 427                 }
 428
 429                 mScrollingChild = view;
 430                 mScrollingChild.Layout.SetPositionByLayout = false;
 431                 propertyNotification = mScrollingChild?.AddPropertyNotification("position", PropertyCondition.Step(1.0f));
 432                 propertyNotification.Notified += OnPropertyChanged;
 433                 mScrollingChild.Relayout += OnScrollingChildRelayout;
 434             }
 435         }
 436
 437         /// <summary>
 438         /// Called after a child has been removed from the owning view.
 439         /// </summary>
 440         /// <param name="view">The child which has been removed.</param>
 441         /// <since_tizen> 6 </since_tizen>
 442         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 443         [EditorBrowsable(EditorBrowsableState.Never)]
 444         public override void OnChildRemove(View view)
 445         {
 446             if (view.Name != "InterruptTouchingChild")
 447             {
 448                 propertyNotification.Notified -= OnPropertyChanged;
 449                 mScrollingChild.RemovePropertyNotification(propertyNotification);
 450                 mScrollingChild.Relayout -= OnScrollingChildRelayout;
 451
 452                 mScrollingChild.Layout.SetPositionByLayout = true;
 453                 mScrollingChild = new View();
 454             }
 455         }
 456
 457         private void OnScrollingChildRelayout(object source, EventArgs args)
 458         {
 459             // Size is changed. Calculate maxScrollDistance.
 460             maxScrollDistance = CalculateMaximumScrollDistance();
 461         }
 462
 463         /// <summary>
 464         /// Scrolls to the item at the specified index.
 465         /// </summary>
 466         /// <param name="index">Index of item.</param>
 467         /// <since_tizen> 6 </since_tizen>
 468         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 469         [EditorBrowsable(EditorBrowsableState.Never)]
 470         public void ScrollToIndex(int index)
 471         {
 472             if (mScrollingChild.ChildCount - 1 < index || index < 0)
 473             {
 474                 return;
 475             }
 476
 477             if (SnapToPage)
 478             {
 479                 CurrentPage = index;
 480             }
 481
 482             float targetPosition = Math.Min(ScrollingDirection == Direction.Vertical ? mScrollingChild.Children[index].Position.Y : mScrollingChild.Children[index].Position.X, maxScrollDistance);
 483             AnimateChildTo(ScrollDuration, -targetPosition);
 484         }
 485
 486         private void OnScrollDragStart()
 487         {
 488             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 489             ScrollDragStartEvent?.Invoke(this, eventArgs);
 490         }
 491
 492         private void OnScrollDragEnd()
 493         {
 494             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 495             ScrollDragEndEvent?.Invoke(this, eventArgs);
 496         }
 497
 498         private void OnScrollAnimationStart()
 499         {
 500             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 501             ScrollAnimationStartEvent?.Invoke(this, eventArgs);
 502         }
 503
 504         private void OnScrollAnimationEnd()
 505         {
 506             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 507             ScrollAnimationEndEvent?.Invoke(this, eventArgs);
 508         }
 509
 510         private bool readyToNotice = false;
 511
 512         private float noticeAnimationEndBeforePosition = 0.0f;
 513         // Let's consider more whether this needs to be set as protected.
 514         public float NoticeAnimationEndBeforePosition { get => noticeAnimationEndBeforePosition; set => noticeAnimationEndBeforePosition = value; }
 515
 516         private void OnScroll()
 517         {
 518             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 519             ScrollEvent?.Invoke(this, eventArgs);
 520
 521             CheckPreReachedTargetPosition();
 522         }
 523
 524         private void CheckPreReachedTargetPosition()
 525         {
 526             // Check whether we reached pre-reached target position
 527             if (readyToNotice &&
 528                 mScrollingChild.CurrentPosition.Y <= finalTargetPosition + NoticeAnimationEndBeforePosition &&
 529                 mScrollingChild.CurrentPosition.Y >= finalTargetPosition - NoticeAnimationEndBeforePosition)
 530             {
 531                 //Notice first
 532                 readyToNotice = false;
 533                 OnPreReachedTargetPosition(finalTargetPosition);
 534             }
 535         }
 536
 537         /// <summary>
 538         /// This helps developer who wants to know before scroll is reaching target position.
 539         /// </summary>
 540         /// <param name="targetPosition">Index of item.</param>
 541         /// <since_tizen> 6 </since_tizen>
 542         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 543         [EditorBrowsable(EditorBrowsableState.Never)]
 544         protected virtual void OnPreReachedTargetPosition(float targetPosition)
 545         {
 546
 547         }
 548
 549         private void StopScroll()
 550         {
 551             if (scrollAnimation != null)
 552             {
 553                 if (scrollAnimation.State == Animation.States.Playing)
 554                 {
 555                     Debug.WriteLineIf(LayoutDebugScrollableBase, "StopScroll Animation Playing");
 556                     scrollAnimation.Stop(Animation.EndActions.Cancel);
 557                     OnScrollAnimationEnd();
 558                 }
 559                 scrollAnimation.Clear();
 560             }
 561         }
 562
 563         // static constructor registers the control type
 564         static ScrollableBase()
 565         {
 566             // ViewRegistry registers control type with DALi type registry
 567             // also uses introspection to find any properties that need to be registered with type registry
 568             CustomViewRegistry.Instance.Register(CreateInstance, typeof(ScrollableBase));
 569         }
 570
 571         internal static CustomView CreateInstance()
 572         {
 573             return new ScrollableBase();
 574         }
 575
 576         private void AnimateChildTo(int duration, float axisPosition)
 577         {
 578             Debug.WriteLineIf(LayoutDebugScrollableBase, "AnimationTo Animation Duration:" + duration + " Destination:" + axisPosition);
 579             finalTargetPosition = axisPosition;
 580
 581             StopScroll(); // Will replace previous animation so will stop existing one.
 582
 583             if (scrollAnimation == null)
 584             {
 585                 scrollAnimation = new Animation();
 586                 scrollAnimation.Finished += ScrollAnimationFinished;
 587             }
 588
 589             scrollAnimation.Duration = duration;
 590             scrollAnimation.DefaultAlphaFunction = new AlphaFunction(AlphaFunction.BuiltinFunctions.EaseOutSine);
 591             scrollAnimation.AnimateTo(mScrollingChild, (ScrollingDirection == Direction.Horizontal) ? "PositionX" : "PositionY", axisPosition);
 592             scrolling = true;
 593             OnScrollAnimationStart();
 594             scrollAnimation.Play();
 595         }
 596
 597         /// <summary>
 598         /// Scroll to specific position with or without animation.
 599         /// </summary>
 600         /// <param name="position">Destination.</param>
 601         /// <param name="animate">Scroll with or without animation</param>
 602         [EditorBrowsable(EditorBrowsableState.Never)]
 603         public void ScrollTo(float position, bool animate)
 604         {
 605             float currentPositionX = mScrollingChild.CurrentPosition.X != 0 ? mScrollingChild.CurrentPosition.X : mScrollingChild.Position.X;
 606             float currentPositionY = mScrollingChild.CurrentPosition.Y != 0 ? mScrollingChild.CurrentPosition.Y : mScrollingChild.Position.Y;
 607             float delta = ScrollingDirection == Direction.Horizontal ? currentPositionX : currentPositionY;
 608             // The argument position is the new pan position. So the new position of ScrollableBase becomes (-position).
 609             // To move ScrollableBase's position to (-position), it moves by (-position - currentPosition).
 610             delta = -position - delta;
 611
 612             ScrollBy(delta, animate);
 613         }
 614
 615         private float BoundScrollPosition(float targetPosition)
 616         {
 617             if (ScrollAvailableArea != null)
 618             {
 619                 float minScrollPosition = ScrollAvailableArea.X;
 620                 float maxScrollPosition = ScrollAvailableArea.Y;
 621
 622                 targetPosition = Math.Min(-minScrollPosition, targetPosition);
 623                 targetPosition = Math.Max(-maxScrollPosition, targetPosition);
 624             }
 625             else
 626             {
 627                 targetPosition = Math.Min(0, targetPosition);
 628                 targetPosition = Math.Max(-maxScrollDistance, targetPosition);
 629             }
 630
 631             return targetPosition;
 632         }
 633
 634         private void ScrollBy(float displacement, bool animate)
 635         {
 636             if (GetChildCount() == 0 || maxScrollDistance < 0)
 637             {
 638                 return;
 639             }
 640
 641             float childCurrentPosition = (ScrollingDirection == Direction.Horizontal) ? mScrollingChild.PositionX : mScrollingChild.PositionY;
 642
 643             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy childCurrentPosition:" + childCurrentPosition +
 644                                                    " displacement:" + displacement,
 645                                                    " maxScrollDistance:" + maxScrollDistance);
 646
 647             childTargetPosition = childCurrentPosition + displacement; // child current position + gesture displacement
 648
 649
 650             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy currentAxisPosition:" + childCurrentPosition + "childTargetPosition:" + childTargetPosition);
 651
 652             if (animate)
 653             {
 654                 // Calculate scroll animaton duration
 655                 float scrollDistance = Math.Abs(displacement);
 656                 int duration = (int)((320 * FlickAnimationSpeed) + (scrollDistance * FlickAnimationSpeed));
 657                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Scroll Animation Duration:" + duration + " Distance:" + scrollDistance);
 658
 659                 readyToNotice = true;
 660
 661                 AnimateChildTo(duration, BoundScrollPosition(AdjustTargetPositionOfScrollAnimation(BoundScrollPosition(childTargetPosition))));
 662             }
 663             else
 664             {
 665                 finalTargetPosition = BoundScrollPosition(childTargetPosition);
 666
 667                 // Set position of scrolling child without an animation
 668                 if (ScrollingDirection == Direction.Horizontal)
 669                 {
 670                     mScrollingChild.PositionX = finalTargetPosition;
 671                 }
 672                 else
 673                 {
 674                     mScrollingChild.PositionY = finalTargetPosition;
 675                 }
 676
 677             }
 678         }
 679
 680         /// <summary>
 681         /// you can override it to clean-up your own resources.
 682         /// </summary>
 683         /// <param name="type">DisposeTypes</param>
 684         /// <since_tizen> 6 </since_tizen>
 685         /// This will be public opened in tizen_5.5 after ACR done. Before ACR, need to be hidden as inhouse API.
 686         [EditorBrowsable(EditorBrowsableState.Never)]
 687         protected override void Dispose(DisposeTypes type)
 688         {
 689             if (disposed)
 690             {
 691                 return;
 692             }
 693
 694             if (type == DisposeTypes.Explicit)
 695             {
 696                 StopScroll();
 697
 698                 if (mPanGestureDetector != null)
 699                 {
 700                     mPanGestureDetector.Detected -= OnPanGestureDetected;
 701                     mPanGestureDetector.Dispose();
 702                     mPanGestureDetector = null;
 703                 }
 704
 705                 if (mTapGestureDetector != null)
 706                 {
 707                     mTapGestureDetector.Detected -= OnTapGestureDetected;
 708                     mTapGestureDetector.Dispose();
 709                     mTapGestureDetector = null;
 710                 }
 711             }
 712             base.Dispose(type);
 713         }
 714
 715         private float CalculateDisplacementFromVelocity(float axisVelocity)
 716         {
 717             // Map: flick speed of range (2.0 - 6.0) to flick multiplier of range (0.7 - 1.6)
 718             float speedMinimum = FlickThreshold;
 719             float speedMaximum = FlickThreshold + 6.0f;
 720             float multiplierMinimum = FlickDistanceMultiplierRange.X;
 721             float multiplierMaximum = FlickDistanceMultiplierRange.Y;
 722
 723             float flickDisplacement = 0.0f;
 724
 725             float speed = Math.Min(4.0f, Math.Abs(axisVelocity));
 726
 727             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollableBase Candidate Flick speed:" + speed);
 728
 729             if (speed > FlickThreshold)
 730             {
 731                 // Flick length is the length of the ScrollableBase.
 732                 float flickLength = (ScrollingDirection == Direction.Horizontal) ? CurrentSize.Width : CurrentSize.Height;
 733
 734                 // Calculate multiplier by mapping speed between the multiplier minimum and maximum.
 735                 multiplier = ((speed - speedMinimum) / ((speedMaximum - speedMinimum) * (multiplierMaximum - multiplierMinimum))) + multiplierMinimum;
 736
 737                 // flick displacement is the product of the flick length and multiplier
 738                 flickDisplacement = ((flickLength * multiplier) * speed) / axisVelocity;  // *speed and /velocity to perserve sign.
 739
 740                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Calculated FlickDisplacement[" + flickDisplacement + "] from speed[" + speed + "] multiplier:"
 741                                                         + multiplier);
 742             }
 743             return flickDisplacement;
 744         }
 745
 746         private float CalculateMaximumScrollDistance()
 747         {
 748             int scrollingChildLength = 0;
 749             int scrollerLength = 0;
 750             if (ScrollingDirection == Direction.Horizontal)
 751             {
 752                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Horizontal");
 753
 754                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredWidth.Size.AsRoundedValue();
 755                 scrollerLength = CurrentSize.Width;
 756             }
 757             else
 758             {
 759                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Vertical");
 760                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredHeight.Size.AsRoundedValue();
 761                 scrollerLength = CurrentSize.Height;
 762             }
 763
 764             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy maxScrollDistance:" + (scrollingChildLength - scrollerLength) +
 765                                                    " parent length:" + scrollerLength +
 766                                                    " scrolling child length:" + scrollingChildLength);
 767
 768             return Math.Max(scrollingChildLength - scrollerLength, 0);
 769         }
 770
 771         private void PageSnap()
 772         {
 773             Debug.WriteLineIf(LayoutDebugScrollableBase, "PageSnap with pan candidate totalDisplacement:" + totalDisplacementForPan +
 774                                                                 " currentPage[" + CurrentPage + "]");
 775
 776             //Increment current page if total displacement enough to warrant a page change.
 777             if (Math.Abs(totalDisplacementForPan) > (mPageWidth * ratioOfScreenWidthToCompleteScroll))
 778             {
 779                 if (totalDisplacementForPan < 0)
 780                 {
 781                     CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1, 0), ++CurrentPage);
 782                 }
 783                 else
 784                 {
 785                     CurrentPage = Math.Max(0, --CurrentPage);
 786                 }
 787             }
 788
 789             // Animate to new page or reposition to current page
 790             float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width / 2 - CurrentSize.Width / 2); // set to middle of current page
 791             Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to page[" + CurrentPage + "] to:" + destinationX + " from:" + mScrollingChild.PositionX);
 792             AnimateChildTo(ScrollDuration, destinationX);
 793         }
 794
 795         private void Flick(float flickDisplacement)
 796         {
 797             if (SnapToPage)
 798             {
 799                 if ((flickWhenAnimating && scrolling == true) || (scrolling == false))
 800                 {
 801                     if (flickDisplacement < 0)
 802                     {
 803                         CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1, 0), CurrentPage + 1);
 804                         Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap - to page:" + CurrentPage);
 805                     }
 806                     else
 807                     {
 808                         CurrentPage = Math.Max(0, CurrentPage - 1);
 809                         Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap + to page:" + CurrentPage);
 810                     }
 811
 812                     float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width / 2.0f - CurrentSize.Width / 2.0f); // set to middle of current page
 813                     Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to :" + destinationX);
 814                     AnimateChildTo(ScrollDuration, destinationX);
 815                 }
 816             }
 817             else
 818             {
 819                 ScrollBy(flickDisplacement, true); // Animate flickDisplacement.
 820             }
 821         }
 822
 823         private void OnPanGestureDetected(object source, PanGestureDetector.DetectedEventArgs e)
 824         {
 825             if (e.PanGesture.State == Gesture.StateType.Started)
 826             {
 827                 Add(mInterruptTouchingChild);
 828                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Gesture Start");
 829                 if (scrolling && !SnapToPage)
 830                 {
 831                     StopScroll();
 832                 }
 833                 totalDisplacementForPan = 0.0f;
 834                 OnScrollDragStart();
 835             }
 836             else if (e.PanGesture.State == Gesture.StateType.Continuing)
 837             {
 838                 if (ScrollingDirection == Direction.Horizontal)
 839                 {
 840                     ScrollBy(e.PanGesture.Displacement.X, false);
 841                     totalDisplacementForPan += e.PanGesture.Displacement.X;
 842                 }
 843                 else
 844                 {
 845                     ScrollBy(e.PanGesture.Displacement.Y, false);
 846                     totalDisplacementForPan += e.PanGesture.Displacement.Y;
 847                 }
 848                 Debug.WriteLineIf(LayoutDebugScrollableBase, "OnPanGestureDetected Continue totalDisplacementForPan:" + totalDisplacementForPan);
 849             }
 850             else if (e.PanGesture.State == Gesture.StateType.Finished)
 851             {
 852                 float axisVelocity = (ScrollingDirection == Direction.Horizontal) ? e.PanGesture.Velocity.X : e.PanGesture.Velocity.Y;
 853                 float flickDisplacement = CalculateDisplacementFromVelocity(axisVelocity);
 854
 855                 Debug.WriteLineIf(LayoutDebugScrollableBase, "FlickDisplacement:" + flickDisplacement + "TotalDisplacementForPan:" + totalDisplacementForPan);
 856                 OnScrollDragEnd();
 857
 858                 if (flickDisplacement > 0 | flickDisplacement < 0)// Flick detected
 859                 {
 860                     Flick(flickDisplacement);
 861                 }
 862                 else
 863                 {
 864                     // End of panning gesture but was not a flick
 865                     if (SnapToPage)
 866                     {
 867                         PageSnap();
 868                     }
 869                     else
 870                     {
 871                         ScrollBy(0, true);
 872                     }
 873                 }
 874                 totalDisplacementForPan = 0;
 875
 876                 Remove(mInterruptTouchingChild);
 877             }
 878         }
 879
 880         private new void OnTapGestureDetected(object source, TapGestureDetector.DetectedEventArgs e)
 881         {
 882             if (e.TapGesture.Type == Gesture.GestureType.Tap)
 883             {
 884                 // Stop scrolling if tap detected (press then relase).
 885                 // Unless in Pages mode, do not want a page change to stop part way.
 886                 if (scrolling && !SnapToPage)
 887                 {
 888                     StopScroll();
 889                 }
 890             }
 891         }
 892
 893         private void ScrollAnimationFinished(object sender, EventArgs e)
 894         {
 895             scrolling = false;
 896             CheckPreReachedTargetPosition();
 897             OnScrollAnimationEnd();
 898         }
 899
 900         /// <summary>
 901         /// Adjust scrolling position by own scrolling rules.
 902         /// Override this function when developer wants to change destination of flicking.(e.g. always snap to center of item)
 903         /// </summary>
 904         /// <since_tizen> 6 </since_tizen>
 905         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 906         [EditorBrowsable(EditorBrowsableState.Never)]
 907         protected virtual float AdjustTargetPositionOfScrollAnimation(float position)
 908         {
 909             return position;
 910         }
 911
 912     }
 913
 914 } // namespace