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                             MeasureChild(childLayout, widthMeasureSpec, unrestrictedMeasureSpec);  // Height unrestricted by parent
  66                         }
  67                         else
  68                         {
  69                             MeasureChild(childLayout, unrestrictedMeasureSpec, heightMeasureSpec);  // 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         protected float finalTargetPosition;
 363
 364         /// <summary>
 365         /// [Draft] Constructor
 366         /// </summary>
 367         /// <since_tizen> 6 </since_tizen>
 368         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 369         [EditorBrowsable(EditorBrowsableState.Never)]
 370         public ScrollableBase() : base()
 371         {
 372             mPanGestureDetector = new PanGestureDetector();
 373             mPanGestureDetector.Attach(this);
 374             mPanGestureDetector.AddDirection(PanGestureDetector.DirectionVertical);
 375             mPanGestureDetector.Detected += OnPanGestureDetected;
 376
 377             mTapGestureDetector = new TapGestureDetector();
 378             mTapGestureDetector.Attach(this);
 379             mTapGestureDetector.Detected += OnTapGestureDetected;
 380
 381
 382             ClippingMode = ClippingModeType.ClipToBoundingBox;
 383
 384             mScrollingChild = new View();
 385             mScrollingChild.Name = "DefaultScrollingChild";
 386
 387             //Interrupt touching when panning is started;
 388             mInterruptTouchingChild = new View()
 389             {
 390                 Name = "InterruptTouchingChild",
 391                 Size = new Size(Window.Instance.WindowSize),
 392                 BackgroundColor = Color.Transparent,
 393             };
 394
 395             mInterruptTouchingChild.TouchEvent += (object source, View.TouchEventArgs args) =>
 396             {
 397                 return true;
 398             };
 399
 400             Layout = new ScrollableBaseCustomLayout();
 401         }
 402
 403         private void OnPropertyChanged(object source, PropertyNotification.NotifyEventArgs args)
 404         {
 405             OnScroll();
 406         }
 407
 408         /// <summary>
 409         /// Called after a child has been added to the owning view.
 410         /// </summary>
 411         /// <param name="view">The child which has been added.</param>
 412         /// <since_tizen> 6 </since_tizen>
 413         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 414         [EditorBrowsable(EditorBrowsableState.Never)]
 415         public override void OnChildAdd(View view)
 416         {
 417             if (view.Name != "InterruptTouchingChild")
 418             {
 419                 if (mScrollingChild.Name != "DefaultScrollingChild")
 420                 {
 421                     propertyNotification.Notified -= OnPropertyChanged;
 422                     mScrollingChild.RemovePropertyNotification(propertyNotification);
 423                 }
 424
 425                 mScrollingChild = view;
 426                 propertyNotification = mScrollingChild?.AddPropertyNotification("position", PropertyCondition.Step(1.0f));
 427                 propertyNotification.Notified += OnPropertyChanged;
 428             }
 429         }
 430
 431         /// <summary>
 432         /// Called after a child has been removed from the owning view.
 433         /// </summary>
 434         /// <param name="view">The child which has been removed.</param>
 435         /// <since_tizen> 6 </since_tizen>
 436         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 437         [EditorBrowsable(EditorBrowsableState.Never)]
 438         public override void OnChildRemove(View view)
 439         {
 440             if (view.Name != "InterruptTouchingChild")
 441             {
 442                 propertyNotification.Notified -= OnPropertyChanged;
 443                 mScrollingChild.RemovePropertyNotification(propertyNotification);
 444
 445                 mScrollingChild = new View();
 446             }
 447         }
 448
 449         /// <summary>
 450         /// Scrolls to the item at the specified index.
 451         /// </summary>
 452         /// <param name="index">Index of item.</param>
 453         /// <since_tizen> 6 </since_tizen>
 454         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 455         [EditorBrowsable(EditorBrowsableState.Never)]
 456         public void ScrollToIndex(int index)
 457         {
 458             if (mScrollingChild.ChildCount - 1 < index || index < 0)
 459             {
 460                 return;
 461             }
 462
 463             if (SnapToPage)
 464             {
 465                 CurrentPage = index;
 466             }
 467
 468             maxScrollDistance = CalculateMaximumScrollDistance();
 469
 470             float targetPosition = Math.Min(ScrollingDirection == Direction.Vertical ? mScrollingChild.Children[index].Position.Y : mScrollingChild.Children[index].Position.X, maxScrollDistance);
 471             AnimateChildTo(ScrollDuration, -targetPosition);
 472         }
 473
 474         private void OnScrollDragStart()
 475         {
 476             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 477             ScrollDragStartEvent?.Invoke(this, eventArgs);
 478         }
 479
 480         private void OnScrollDragEnd()
 481         {
 482             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 483             ScrollDragEndEvent?.Invoke(this, eventArgs);
 484         }
 485
 486         private void OnScrollAnimationStart()
 487         {
 488             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 489             ScrollAnimationStartEvent?.Invoke(this, eventArgs);
 490         }
 491
 492         private void OnScrollAnimationEnd()
 493         {
 494             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 495             ScrollAnimationEndEvent?.Invoke(this, eventArgs);
 496         }
 497
 498         private bool readyToNotice = false;
 499
 500         protected float noticeAnimationEndBeforePosition = 0.0f;
 501
 502         private void OnScroll()
 503         {
 504             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 505             ScrollEvent?.Invoke(this, eventArgs);
 506
 507             CheckPreReachedTargetPosition();
 508         }
 509
 510         private void CheckPreReachedTargetPosition()
 511         {
 512             // Check whether we reached pre-reached target position
 513             if (readyToNotice &&
 514                 mScrollingChild.CurrentPosition.Y <= finalTargetPosition + noticeAnimationEndBeforePosition &&
 515                 mScrollingChild.CurrentPosition.Y >= finalTargetPosition - noticeAnimationEndBeforePosition)
 516             {
 517                 //Notice first
 518                 readyToNotice = false;
 519                 OnPreReachedTargetPosition(finalTargetPosition);
 520             }
 521         }
 522
 523         /// <summary>
 524         /// This helps developer who wants to know before scroll is reaching target position.
 525         /// </summary>
 526         /// <param name="targetPosition">Index of item.</param>
 527         /// <since_tizen> 6 </since_tizen>
 528         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 529         [EditorBrowsable(EditorBrowsableState.Never)]
 530         protected virtual void OnPreReachedTargetPosition(float targetPosition)
 531         {
 532
 533         }
 534
 535         private void StopScroll()
 536         {
 537             if (scrollAnimation != null)
 538             {
 539                 if (scrollAnimation.State == Animation.States.Playing)
 540                 {
 541                     Debug.WriteLineIf(LayoutDebugScrollableBase, "StopScroll Animation Playing");
 542                     scrollAnimation.Stop(Animation.EndActions.Cancel);
 543                     OnScrollAnimationEnd();
 544                 }
 545                 scrollAnimation.Clear();
 546             }
 547         }
 548
 549         // static constructor registers the control type
 550         static ScrollableBase()
 551         {
 552             // ViewRegistry registers control type with DALi type registry
 553             // also uses introspection to find any properties that need to be registered with type registry
 554             CustomViewRegistry.Instance.Register(CreateInstance, typeof(ScrollableBase));
 555         }
 556
 557         internal static CustomView CreateInstance()
 558         {
 559             return new ScrollableBase();
 560         }
 561
 562         private void AnimateChildTo(int duration, float axisPosition)
 563         {
 564             Debug.WriteLineIf(LayoutDebugScrollableBase, "AnimationTo Animation Duration:" + duration + " Destination:" + axisPosition);
 565             finalTargetPosition = axisPosition;
 566
 567             StopScroll(); // Will replace previous animation so will stop existing one.
 568
 569             if (scrollAnimation == null)
 570             {
 571                 scrollAnimation = new Animation();
 572                 scrollAnimation.Finished += ScrollAnimationFinished;
 573             }
 574
 575             scrollAnimation.Duration = duration;
 576             scrollAnimation.DefaultAlphaFunction = new AlphaFunction(AlphaFunction.BuiltinFunctions.EaseOutSine);
 577             scrollAnimation.AnimateTo(mScrollingChild, (ScrollingDirection == Direction.Horizontal) ? "PositionX" : "PositionY", axisPosition);
 578             scrolling = true;
 579             OnScrollAnimationStart();
 580             scrollAnimation.Play();
 581         }
 582
 583         /// <summary>
 584         /// Scroll to specific position with or without animation.
 585         /// </summary>
 586         /// <param name="position">Destination.</param>
 587         /// <param name="animate">Scroll with or without animation</param>
 588         [EditorBrowsable(EditorBrowsableState.Never)]
 589         public void ScrollTo(float position, bool animate)
 590         {
 591             float currentPositionX = mScrollingChild.CurrentPosition.X != 0 ? mScrollingChild.CurrentPosition.X : mScrollingChild.Position.X;
 592             float currentPositionY = mScrollingChild.CurrentPosition.Y != 0 ? mScrollingChild.CurrentPosition.Y : mScrollingChild.Position.Y;
 593             float delta = ScrollingDirection == Direction.Horizontal ? currentPositionX : currentPositionY;
 594             delta -= position;
 595
 596             ScrollBy(delta, animate);
 597         }
 598
 599         private float BoundScrollPosition(float targetPosition)
 600         {
 601             if (ScrollAvailableArea != null)
 602             {
 603                 float minScrollPosition = ScrollAvailableArea.X;
 604                 float maxScrollPosition = ScrollAvailableArea.Y;
 605
 606                 targetPosition = Math.Min(-minScrollPosition, targetPosition);
 607                 targetPosition = Math.Max(-maxScrollPosition, targetPosition);
 608             }
 609             else
 610             {
 611                 targetPosition = Math.Min(0, targetPosition);
 612                 targetPosition = Math.Max(-maxScrollDistance, targetPosition);
 613             }
 614
 615             return targetPosition;
 616         }
 617
 618         private void ScrollBy(float displacement, bool animate)
 619         {
 620             if (GetChildCount() == 0 || maxScrollDistance < 0)
 621             {
 622                 return;
 623             }
 624
 625             float childCurrentPosition = (ScrollingDirection == Direction.Horizontal) ? mScrollingChild.PositionX : mScrollingChild.PositionY;
 626
 627             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy childCurrentPosition:" + childCurrentPosition +
 628                                                    " displacement:" + displacement,
 629                                                    " maxScrollDistance:" + maxScrollDistance);
 630
 631             childTargetPosition = childCurrentPosition + displacement; // child current position + gesture displacement
 632
 633
 634             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy currentAxisPosition:" + childCurrentPosition + "childTargetPosition:" + childTargetPosition);
 635
 636             if (animate)
 637             {
 638                 // Calculate scroll animaton duration
 639                 float scrollDistance = Math.Abs(displacement);
 640                 int duration = (int)((320 * FlickAnimationSpeed) + (scrollDistance * FlickAnimationSpeed));
 641                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Scroll Animation Duration:" + duration + " Distance:" + scrollDistance);
 642
 643                 readyToNotice = true;
 644
 645                 AnimateChildTo(duration, BoundScrollPosition(AdjustTargetPositionOfScrollAnimation(BoundScrollPosition(childTargetPosition))));
 646             }
 647             else
 648             {
 649                 finalTargetPosition = BoundScrollPosition(childTargetPosition);
 650
 651                 // Set position of scrolling child without an animation
 652                 if (ScrollingDirection == Direction.Horizontal)
 653                 {
 654                     mScrollingChild.PositionX = finalTargetPosition;
 655                 }
 656                 else
 657                 {
 658                     mScrollingChild.PositionY = finalTargetPosition;
 659                 }
 660
 661             }
 662         }
 663
 664         /// <summary>
 665         /// you can override it to clean-up your own resources.
 666         /// </summary>
 667         /// <param name="type">DisposeTypes</param>
 668         /// <since_tizen> 6 </since_tizen>
 669         /// This will be public opened in tizen_5.5 after ACR done. Before ACR, need to be hidden as inhouse API.
 670         [EditorBrowsable(EditorBrowsableState.Never)]
 671         protected override void Dispose(DisposeTypes type)
 672         {
 673             if (disposed)
 674             {
 675                 return;
 676             }
 677
 678             if (type == DisposeTypes.Explicit)
 679             {
 680                 StopScroll();
 681
 682                 if (mPanGestureDetector != null)
 683                 {
 684                     mPanGestureDetector.Detected -= OnPanGestureDetected;
 685                     mPanGestureDetector.Dispose();
 686                     mPanGestureDetector = null;
 687                 }
 688
 689                 if (mTapGestureDetector != null)
 690                 {
 691                     mTapGestureDetector.Detected -= OnTapGestureDetected;
 692                     mTapGestureDetector.Dispose();
 693                     mTapGestureDetector = null;
 694                 }
 695             }
 696             base.Dispose(type);
 697         }
 698
 699         private float CalculateDisplacementFromVelocity(float axisVelocity)
 700         {
 701             // Map: flick speed of range (2.0 - 6.0) to flick multiplier of range (0.7 - 1.6)
 702             float speedMinimum = FlickThreshold;
 703             float speedMaximum = FlickThreshold + 6.0f;
 704             float multiplierMinimum = FlickDistanceMultiplierRange.X;
 705             float multiplierMaximum = FlickDistanceMultiplierRange.Y;
 706
 707             float flickDisplacement = 0.0f;
 708
 709             float speed = Math.Min(4.0f, Math.Abs(axisVelocity));
 710
 711             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollableBase Candidate Flick speed:" + speed);
 712
 713             if (speed > FlickThreshold)
 714             {
 715                 // Flick length is the length of the ScrollableBase.
 716                 float flickLength = (ScrollingDirection == Direction.Horizontal) ? CurrentSize.Width : CurrentSize.Height;
 717
 718                 // Calculate multiplier by mapping speed between the multiplier minimum and maximum.
 719                 multiplier = ((speed - speedMinimum) / ((speedMaximum - speedMinimum) * (multiplierMaximum - multiplierMinimum))) + multiplierMinimum;
 720
 721                 // flick displacement is the product of the flick length and multiplier
 722                 flickDisplacement = ((flickLength * multiplier) * speed) / axisVelocity;  // *speed and /velocity to perserve sign.
 723
 724                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Calculated FlickDisplacement[" + flickDisplacement + "] from speed[" + speed + "] multiplier:"
 725                                                         + multiplier);
 726             }
 727             return flickDisplacement;
 728         }
 729
 730         private float CalculateMaximumScrollDistance()
 731         {
 732             int scrollingChildLength = 0;
 733             int scrollerLength = 0;
 734             if (ScrollingDirection == Direction.Horizontal)
 735             {
 736                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Horizontal");
 737
 738                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredWidth.Size.AsRoundedValue();
 739                 scrollerLength = CurrentSize.Width;
 740             }
 741             else
 742             {
 743                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Vertical");
 744                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredHeight.Size.AsRoundedValue();
 745                 scrollerLength = CurrentSize.Height;
 746             }
 747
 748             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy maxScrollDistance:" + (scrollingChildLength - scrollerLength) +
 749                                                    " parent length:" + scrollerLength +
 750                                                    " scrolling child length:" + scrollingChildLength);
 751
 752             return Math.Max(scrollingChildLength - scrollerLength, 0);
 753         }
 754
 755         private void PageSnap()
 756         {
 757             Debug.WriteLineIf(LayoutDebugScrollableBase, "PageSnap with pan candidate totalDisplacement:" + totalDisplacementForPan +
 758                                                                 " currentPage[" + CurrentPage + "]");
 759
 760             //Increment current page if total displacement enough to warrant a page change.
 761             if (Math.Abs(totalDisplacementForPan) > (mPageWidth * ratioOfScreenWidthToCompleteScroll))
 762             {
 763                 if (totalDisplacementForPan < 0)
 764                 {
 765                     CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1, 0), ++CurrentPage);
 766                 }
 767                 else
 768                 {
 769                     CurrentPage = Math.Max(0, --CurrentPage);
 770                 }
 771             }
 772
 773             // Animate to new page or reposition to current page
 774             float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width / 2 - CurrentSize.Width / 2); // set to middle of current page
 775             Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to page[" + CurrentPage + "] to:" + destinationX + " from:" + mScrollingChild.PositionX);
 776             AnimateChildTo(ScrollDuration, destinationX);
 777         }
 778
 779         private void Flick(float flickDisplacement)
 780         {
 781             if (SnapToPage)
 782             {
 783                 if ((flickWhenAnimating && scrolling == true) || (scrolling == false))
 784                 {
 785                     if (flickDisplacement < 0)
 786                     {
 787                         CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1, 0), CurrentPage + 1);
 788                         Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap - to page:" + CurrentPage);
 789                     }
 790                     else
 791                     {
 792                         CurrentPage = Math.Max(0, CurrentPage - 1);
 793                         Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap + to page:" + CurrentPage);
 794                     }
 795
 796                     float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width / 2.0f - CurrentSize.Width / 2.0f); // set to middle of current page
 797                     Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to :" + destinationX);
 798                     AnimateChildTo(ScrollDuration, destinationX);
 799                 }
 800             }
 801             else
 802             {
 803                 ScrollBy(flickDisplacement, true); // Animate flickDisplacement.
 804             }
 805         }
 806
 807         private void OnPanGestureDetected(object source, PanGestureDetector.DetectedEventArgs e)
 808         {
 809             if (e.PanGesture.State == Gesture.StateType.Started)
 810             {
 811                 Add(mInterruptTouchingChild);
 812                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Gesture Start");
 813                 if (scrolling && !SnapToPage)
 814                 {
 815                     StopScroll();
 816                 }
 817                 maxScrollDistance = CalculateMaximumScrollDistance();
 818                 totalDisplacementForPan = 0.0f;
 819                 OnScrollDragStart();
 820             }
 821             else if (e.PanGesture.State == Gesture.StateType.Continuing)
 822             {
 823                 if (ScrollingDirection == Direction.Horizontal)
 824                 {
 825                     ScrollBy(e.PanGesture.Displacement.X, false);
 826                     totalDisplacementForPan += e.PanGesture.Displacement.X;
 827                 }
 828                 else
 829                 {
 830                     ScrollBy(e.PanGesture.Displacement.Y, false);
 831                     totalDisplacementForPan += e.PanGesture.Displacement.Y;
 832                 }
 833                 Debug.WriteLineIf(LayoutDebugScrollableBase, "OnPanGestureDetected Continue totalDisplacementForPan:" + totalDisplacementForPan);
 834             }
 835             else if (e.PanGesture.State == Gesture.StateType.Finished)
 836             {
 837                 float axisVelocity = (ScrollingDirection == Direction.Horizontal) ? e.PanGesture.Velocity.X : e.PanGesture.Velocity.Y;
 838                 float flickDisplacement = CalculateDisplacementFromVelocity(axisVelocity);
 839
 840                 Debug.WriteLineIf(LayoutDebugScrollableBase, "FlickDisplacement:" + flickDisplacement + "TotalDisplacementForPan:" + totalDisplacementForPan);
 841                 OnScrollDragEnd();
 842
 843                 if (flickDisplacement > 0 | flickDisplacement < 0)// Flick detected
 844                 {
 845                     Flick(flickDisplacement);
 846                 }
 847                 else
 848                 {
 849                     // End of panning gesture but was not a flick
 850                     if (SnapToPage)
 851                     {
 852                         PageSnap();
 853                     }
 854                     else
 855                     {
 856                         ScrollBy(0, true);
 857                     }
 858                 }
 859                 totalDisplacementForPan = 0;
 860
 861                 Remove(mInterruptTouchingChild);
 862             }
 863         }
 864
 865         private new void OnTapGestureDetected(object source, TapGestureDetector.DetectedEventArgs e)
 866         {
 867             if (e.TapGesture.Type == Gesture.GestureType.Tap)
 868             {
 869                 // Stop scrolling if tap detected (press then relase).
 870                 // Unless in Pages mode, do not want a page change to stop part way.
 871                 if (scrolling && !SnapToPage)
 872                 {
 873                     StopScroll();
 874                 }
 875             }
 876         }
 877
 878         private void ScrollAnimationFinished(object sender, EventArgs e)
 879         {
 880             scrolling = false;
 881             CheckPreReachedTargetPosition();
 882             OnScrollAnimationEnd();
 883         }
 884
 885         /// <summary>
 886         /// Adjust scrolling position by own scrolling rules.
 887         /// Override this function when developer wants to change destination of flicking.(e.g. always snap to center of item)
 888         /// </summary>
 889         /// <since_tizen> 6 </since_tizen>
 890         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 891         [EditorBrowsable(EditorBrowsableState.Never)]
 892         protected virtual float AdjustTargetPositionOfScrollAnimation(float position)
 893         {
 894             return position;
 895         }
 896
 897     }
 898
 899 } // namespace