content: /*
   * Copyright (C) 2013 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.haarman.listviewanimations.view;
  
  import android.content.Context;
  import android.graphics.Bitmap;
  import android.graphics.Canvas;
  import android.graphics.Rect;
  import android.graphics.drawable.BitmapDrawable;
  import android.graphics.drawable.Drawable;
  import android.util.AttributeSet;
  import android.util.DisplayMetrics;
  import android.view.MotionEvent;
  import android.view.View;
  import android.view.ViewConfiguration;
  import android.view.ViewGroup;
  import android.view.ViewTreeObserver;
  import android.widget.AbsListView;
  import android.widget.AdapterView;
  import android.widget.BaseAdapter;
  import android.widget.ListAdapter;
  import android.widget.ListView;
  
  import com.haarman.listviewanimations.itemmanipulation.SwipeOnTouchListener;
  import com.nineoldandroids.animation.Animator;
  import com.nineoldandroids.animation.AnimatorListenerAdapter;
  import com.nineoldandroids.animation.ObjectAnimator;
  import com.nineoldandroids.animation.TypeEvaluator;
  import com.nineoldandroids.animation.ValueAnimator;
  import com.nineoldandroids.view.ViewHelper;
  
  /**
   * The DynamicListView is an extension of {@link ListView} that supports cell dragging
   * and swapping.
   * </p>
   * Make sure your adapter has stable ids, and override {@link ListAdapter#hasStableIds()} to return true.</br>
   * </p>
   * This layout is in charge of positioning the hover cell in the correct location
   * on the screen in response to user touch events. It uses the position of the
   * hover cell to determine when two cells should be swapped. If two cells should
   * be swapped, all the corresponding data set and layout changes are handled here.
   * </p>
   * If no cell is selected, all the touch events are passed down to the ListView
   * and behave normally. If one of the items in the ListView experiences a
   * long press event, the contents of its current visible state are captured as
   * a bitmap and its visibility is set to INVISIBLE. A hover cell is then created and
   * added to this layout as an overlaying BitmapDrawable above the ListView. Once the
   * hover cell is translated some distance to signify an item swap, a data set change
   * accompanied by animation takes place. When the user releases the hover cell,
   * it animates into its corresponding position in the ListView.
   * </p>
   * When the hover cell is either above or below the bounds of the ListView, this
   * ListView also scrolls on its own so as to reveal additional content.
   * </p>
   * See http://youtu.be/_BZIvjMgH-Q
   */
  public class DynamicListView extends ListView {
  
  	public interface OnHoverCellListener {
  		public Drawable onHoverCellCreated(Drawable hoverCellDrawable);
  	}
  
  	private final int SMOOTH_SCROLL_AMOUNT_AT_EDGE = 15;
  	private final int MOVE_DURATION = 150;
  
  	private int mLastEventY = -1, mLastEventX = -1;
  
  	private int mDownY = -1;
  	private int mDownX = -1;
  
  	private int mTotalOffset = 0;
  
  	private boolean mCellIsMobile = false;
  	private boolean mIsMobileScrolling = false;
  	private int mSmoothScrollAmountAtEdge = 0;
  
  	private final int INVALID_ID = -1;
  	private long mAboveItemId = INVALID_ID;
  	private long mMobileItemId = INVALID_ID;
  	private long mBelowItemId = INVALID_ID;
  
  	private Drawable mHoverCell;
  	private Rect mHoverCellCurrentBounds;
  	private Rect mHoverCellOriginalBounds;
  
  	private final int INVALID_POINTER_ID = -1;
  	private int mActivePointerId = INVALID_POINTER_ID;
  
  	private boolean mIsWaitingForScrollFinish = false;
  	private int mScrollState = OnScrollListener.SCROLL_STATE_IDLE;
  
  	private OnTouchListener mOnTouchListener;
  	private boolean mIsParentHorizontalScrollContainer;
  	private int mResIdOfDynamicTouchChild;
  	private boolean mDynamicTouchChildTouched;
  	private int mSlop;
  
  	private boolean mSkipCallingOnTouchListener;
  
  	private OnHoverCellListener mOnHoverCellListener;
  
  	public DynamicListView(Context context) {
  		super(context);
  		init(context);
  	}
  
  	public DynamicListView(Context context, AttributeSet attrs, int defStyle) {
  		super(context, attrs, defStyle);
  		init(context);
  	}
  
  	public DynamicListView(Context context, AttributeSet attrs) {
  		super(context, attrs);
  		init(context);
  	}
  
  	public void init(Context context) {
  		setOnItemLongClickListener(mOnItemLongClickListener);
  		setOnScrollListener(mScrollListener);
  		DisplayMetrics metrics = context.getResources().getDisplayMetrics();
  		mSmoothScrollAmountAtEdge = (int) (SMOOTH_SCROLL_AMOUNT_AT_EDGE / metrics.density);
  		ViewConfiguration vc = ViewConfiguration.get(getContext());
  		mSlop = vc.getScaledTouchSlop();
  	}
  
  	/**
  	 * Listens for long clicks on any items in the listview. When a cell has
  	 * been selected, the hover cell is created and set up.
  	 */
  	private OnItemLongClickListener mOnItemLongClickListener = new OnItemLongClickListener() {
  		public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int pos, long id) {
  			if (mResIdOfDynamicTouchChild == 0) {
  				mDynamicTouchChildTouched = true;
  				makeCellMobile();
  				return true;
  			}
  			return false;
  		}
  	};
  
  	private void makeCellMobile() {
  		int position = pointToPosition(mDownX, mDownY);
  		int itemNum = position - getFirstVisiblePosition();
  		View selectedView = getChildAt(itemNum);
  		if (selectedView == null) {
  			return;
  		}
  
  		mTotalOffset = 0;
  
  		mMobileItemId = getAdapter().getItemId(position);
  		mHoverCell = getAndAddHoverView(selectedView);
  		if (mOnHoverCellListener != null) {
  			mHoverCell = mOnHoverCellListener.onHoverCellCreated(mHoverCell);
  		}
  		selectedView.setVisibility(INVISIBLE);
  
  		mCellIsMobile = true;
  		getParent().requestDisallowInterceptTouchEvent(true);
  
  		updateNeighborViewsForID(mMobileItemId);
  
  	}
  
  	/**
  	 * Creates the hover cell with the appropriate bitmap and of appropriate
  	 * size. The hover cell's BitmapDrawable is drawn on top of the bitmap every
  	 * single time an invalidate call is made.
  	 */
  	private BitmapDrawable getAndAddHoverView(View v) {
  
  		int w = v.getWidth();
  		int h = v.getHeight();
  		int top = v.getTop();
  		int left = v.getLeft();
  
  		Bitmap b = getBitmapFromView(v);
  
  		BitmapDrawable drawable = new BitmapDrawable(getResources(), b);
  
  		mHoverCellOriginalBounds = new Rect(left, top, left + w, top + h);
  		mHoverCellCurrentBounds = new Rect(mHoverCellOriginalBounds);
  
  		drawable.setBounds(mHoverCellCurrentBounds);
  
  		return drawable;
  	}
  
  	/** Returns a bitmap showing a screenshot of the view passed in. */
  	private Bitmap getBitmapFromView(View v) {
  		Bitmap bitmap = Bitmap.createBitmap(v.getWidth(), v.getHeight(), Bitmap.Config.ARGB_8888);
  		Canvas canvas = new Canvas(bitmap);
  		v.draw(canvas);
  		return bitmap;
  	}
  
  	/**
  	 * Stores a reference to the views above and below the item currently
  	 * corresponding to the hover cell. It is important to note that if this
  	 * item is either at the top or bottom of the list, mAboveItemId or mBelowItemId
  	 * may be invalid.
  	 */
  	private void updateNeighborViewsForID(long itemID) {
  		int position = getPositionForID(itemID);
  		BaseAdapter adapter = (BaseAdapter) getAdapter();
  		if (!adapter.hasStableIds()) {
  			throw new IllegalStateException("Adapter doesn't have stable ids! Make sure your adapter has stable ids, and override hasStableIds() to return true.");
  		}
  
  		mAboveItemId = position - 1 >= 0 ? adapter.getItemId(position - 1) : INVALID_ROW_ID;
  		mBelowItemId = position + 1 < adapter.getCount() ? adapter.getItemId(position + 1) : INVALID_ROW_ID;
  	}
  
  	/** Retrieves the view in the list corresponding to itemID */
  	public View getViewForID(long itemID) {
  		int firstVisiblePosition = getFirstVisiblePosition();
  		BaseAdapter adapter = (BaseAdapter) getAdapter();
  		if (!adapter.hasStableIds()) {
  			throw new IllegalStateException("Adapter doesn't have stable ids! Make sure your adapter has stable ids, and override hasStableIds() to return true.");
  		}
  
  		for (int i = 0; i < getChildCount(); i++) {
  			View v = getChildAt(i);
  			int position = firstVisiblePosition + i;
  			long id = adapter.getItemId(position);
  			if (id == itemID) {
  				return v;
  			}
  		}
  		return null;
  	}
  
  	/** Retrieves the position in the list corresponding to itemID */
  	public int getPositionForID(long itemID) {
  		View v = getViewForID(itemID);
  		if (v == null) {
  			return -1;
  		} else {
  			return getPositionForView(v);
  		}
  	}
  
  	/**
  	 *  dispatchDraw gets invoked when all the child views are about to be drawn.
  	 *  By overriding this method, the hover cell (BitmapDrawable) can be drawn
  	 *  over the listview's items whenever the listview is redrawn.
  	 */
  	@Override
  	protected void dispatchDraw(Canvas canvas) {
  		super.dispatchDraw(canvas);
  		if (mHoverCell != null) {
  			mHoverCell.draw(canvas);
  		}
  	}
  
  	@Override
  	public void setOnTouchListener(OnTouchListener l) {
  		mOnTouchListener = l;
  	}
  
  	public void setOnHoverCellListener(OnHoverCellListener onHoverCellListener) {
  		mOnHoverCellListener = onHoverCellListener;
  	}
  
  	private Rect getChildViewRect(View parentView, View childView) {
  		final Rect childRect = new Rect(childView.getLeft(), childView.getTop(), childView.getRight(), childView.getBottom());
  		if (parentView == childView) {
  			return childRect;
  		}
  
  		ViewGroup parent;
  		while ((parent = (ViewGroup) childView.getParent()) != parentView) {
  			childRect.offset(parent.getLeft(), parent.getTop());
  			childView = parent;
  		}
  
  		return childRect;
  	}
  
  	@Override
  	public boolean onTouchEvent(MotionEvent event) {
  		if (mSkipCallingOnTouchListener) {
  			return super.onTouchEvent(event);
  		}
  
  		if (mOnTouchListener instanceof SwipeOnTouchListener) {
  			if (((SwipeOnTouchListener) mOnTouchListener).isSwiping()) {
  				mSkipCallingOnTouchListener = true;
  				boolean retVal = mOnTouchListener.onTouch(this, event);
  				mSkipCallingOnTouchListener = false;
  				return retVal ? true : super.onTouchEvent(event);
  			}
  		}
  
  		switch (event.getAction() & MotionEvent.ACTION_MASK) {
  		case MotionEvent.ACTION_DOWN:
  			mDownX = (int) event.getX();
  			mDownY = (int) event.getY();
  			mActivePointerId = event.getPointerId(0);
  
  			mDynamicTouchChildTouched = false;
  			if (mResIdOfDynamicTouchChild != 0) {
  				mIsParentHorizontalScrollContainer = false;
  
  				int position = pointToPosition(mDownX, mDownY);
  				int childNum = (position != INVALID_POSITION) ? position - getFirstVisiblePosition() : -1;
  				View itemView = (childNum >= 0) ? getChildAt(childNum) : null;
  				View childView = (itemView != null) ? itemView.findViewById(mResIdOfDynamicTouchChild) : null;
  				if (childView != null) {
  					final Rect childRect = getChildViewRect(this, childView);
  					if (childRect.contains(mDownX, mDownY)) {
  						mDynamicTouchChildTouched = true;
  						getParent().requestDisallowInterceptTouchEvent(true);
  					}
  				}
  			}
  
  			if (mIsParentHorizontalScrollContainer) {
  				// Do it now and don't wait until the user moves more than the
  				// slop factor.
  				getParent().requestDisallowInterceptTouchEvent(true);
  			}
  			break;
  		case MotionEvent.ACTION_MOVE:
  			if (mActivePointerId == INVALID_POINTER_ID) {
  				break;
  			}
  
  			int pointerIndex = event.findPointerIndex(mActivePointerId);
  
  			mLastEventY = (int) event.getY(pointerIndex);
  			mLastEventX = (int) event.getX(pointerIndex);
  			int deltaY = mLastEventY - mDownY;
  			int deltaX = mLastEventX - mDownX;
  
  			if (!mCellIsMobile && mDynamicTouchChildTouched) {
  				if ((Math.abs(deltaY) > mSlop) && (Math.abs(deltaY) > Math.abs(deltaX))) {
  					makeCellMobile();
  
  					// Cancel ListView's touch (un-highlighting the item)
  					MotionEvent cancelEvent = MotionEvent.obtain(event);
  					cancelEvent.setAction(MotionEvent.ACTION_CANCEL | (event.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));
  					super.onTouchEvent(cancelEvent);
  					cancelEvent.recycle();
  				}
  			}
  
  			if (mCellIsMobile) {
  				mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mHoverCellOriginalBounds.top + deltaY + mTotalOffset);
  				mHoverCell.setBounds(mHoverCellCurrentBounds);
  				invalidate();
  
  				handleCellSwitch();
  
  				mIsMobileScrolling = false;
  				handleMobileCellScroll();
  			}
  			break;
  		case MotionEvent.ACTION_UP:
  			mDynamicTouchChildTouched = false;
  			touchEventsEnded();
  			break;
  		case MotionEvent.ACTION_CANCEL:
  			mDynamicTouchChildTouched = false;
  			touchEventsCancelled();
  			break;
  		case MotionEvent.ACTION_POINTER_UP:
  			/*
  			 * If a multitouch event took place and the original touch dictating
  			 * the movement of the hover cell has ended, then the dragging event
  			 * ends and the hover cell is animated to its corresponding position
  			 * in the listview.
  			 */
  			pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
  			final int pointerId = event.getPointerId(pointerIndex);
  			if (pointerId == mActivePointerId) {
  				mDynamicTouchChildTouched = false;
  				touchEventsEnded();
  			}
  			break;
  		default:
  			break;
  		}
  
  		if (mCellIsMobile) {
  			return false;
  		} else if (mOnTouchListener != null) {
  			mSkipCallingOnTouchListener = true;
  			boolean retVal = mOnTouchListener.onTouch(this, event);
  			mSkipCallingOnTouchListener = false;
  			if (retVal) {
  				return true;
  			}
  		}
  		return super.onTouchEvent(event);
  	}
  
  	/**
  	 * This method determines whether the hover cell has been shifted far enough
  	 * to invoke a cell swap. If so, then the respective cell swap candidate is
  	 * determined and the data set is changed. Upon posting a notification of the
  	 * data set change, a layout is invoked to place the cells in the right place.
  	 * Using a ViewTreeObserver and a corresponding OnPreDrawListener, we can
  	 * offset the cell being swapped to where it previously was and then animate it to
  	 * its new position.
  	 */
  	private void handleCellSwitch() {
  		final int deltaY = mLastEventY - mDownY;
  		int deltaYTotal = mHoverCellOriginalBounds.top + mTotalOffset + deltaY;
  
  		View belowView = getViewForID(mBelowItemId);
  		View mobileView = getViewForID(mMobileItemId);
  		View aboveView = getViewForID(mAboveItemId);
  
  		boolean isBelow = (belowView != null) && (deltaYTotal > belowView.getTop());
  		boolean isAbove = (aboveView != null) && (deltaYTotal < aboveView.getTop());
  
  		if (isBelow || isAbove) {
  
  			final long switchItemID = isBelow ? mBelowItemId : mAboveItemId;
  			View switchView = isBelow ? belowView : aboveView;
  			final int originalItem = getPositionForView(mobileView);
  
  			if (switchView == null) {
  				updateNeighborViewsForID(mMobileItemId);
  				return;
  			}
  
  			swapElements(originalItem, getPositionForView(switchView));
  
  			((BaseAdapter) getAdapter()).notifyDataSetChanged();
  
  			mDownY = mLastEventY;
  			mDownX = mLastEventX;
  
  			final int switchViewStartTop = switchView.getTop();
  
  			mobileView.setVisibility(View.VISIBLE);
  			switchView.setVisibility(View.INVISIBLE);
  
  			updateNeighborViewsForID(mMobileItemId);
  
  			final ViewTreeObserver observer = getViewTreeObserver();
  			observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
  				public boolean onPreDraw() {
  					observer.removeOnPreDrawListener(this);
  
  					View switchView = getViewForID(switchItemID);
  
  					mTotalOffset += deltaY;
  
  					int switchViewNewTop = switchView.getTop();
  					int delta = switchViewStartTop - switchViewNewTop;
  
  					ViewHelper.setTranslationY(switchView, delta);
  
  					ObjectAnimator animator = ObjectAnimator.ofFloat(switchView, "translationY", 0);
  					animator.setDuration(MOVE_DURATION);
  					animator.start();
  
  					return true;
  				}
  			});
  		}
  	}
  
  	private void swapElements(int indexOne, int indexTwo) {
  		ListAdapter adapter = getAdapter();
  		if (adapter instanceof Swappable) {
  			((Swappable) adapter).swapItems(indexOne, indexTwo);
  		}
  	}
  
  	/**
  	 * Resets all the appropriate fields to a default state while also animating
  	 * the hover cell back to its correct location.
  	 */
  	private void touchEventsEnded() {
  		final View mobileView = getViewForID(mMobileItemId);
  		if (mCellIsMobile || mIsWaitingForScrollFinish) {
  			mCellIsMobile = false;
  			mIsWaitingForScrollFinish = false;
  			mIsMobileScrolling = false;
  			mActivePointerId = INVALID_POINTER_ID;
  
  			// If the autoscroller has not completed scrolling, we need to wait
  			// for it to
  			// finish in order to determine the final location of where the
  			// hover cell
  			// should be animated to.
  			if (mScrollState != OnScrollListener.SCROLL_STATE_IDLE) {
  				mIsWaitingForScrollFinish = true;
  				return;
  			}
  
  			mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mobileView.getTop());
  
  			ObjectAnimator hoverViewAnimator = ObjectAnimator.ofObject(mHoverCell, "bounds", sBoundEvaluator, mHoverCellCurrentBounds);
  			hoverViewAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  				@Override
  				public void onAnimationUpdate(ValueAnimator valueAnimator) {
  					invalidate();
  				}
  			});
  			hoverViewAnimator.addListener(new AnimatorListenerAdapter() {
  				@Override
  				public void onAnimationStart(Animator animation) {
  					setEnabled(false);
  				}
  
  				@Override
  				public void onAnimationEnd(Animator animation) {
  					mAboveItemId = INVALID_ID;
  					mMobileItemId = INVALID_ID;
  					mBelowItemId = INVALID_ID;
  					mobileView.setVisibility(VISIBLE);
  					mHoverCell = null;
  					setEnabled(true);
  					invalidate();
  				}
  			});
  			hoverViewAnimator.start();
  		} else {
  			touchEventsCancelled();
  		}
  	}
  
  	/**
  	 * Resets all the appropriate fields to a default state.
  	 */
  	private void touchEventsCancelled() {
  		View mobileView = getViewForID(mMobileItemId);
  		if (mCellIsMobile) {
  			mAboveItemId = INVALID_ID;
  			mMobileItemId = INVALID_ID;
  			mBelowItemId = INVALID_ID;
  			mobileView.setVisibility(VISIBLE);
  			mHoverCell = null;
  			invalidate();
  		}
  		mCellIsMobile = false;
  		mIsMobileScrolling = false;
  		mActivePointerId = INVALID_POINTER_ID;
  	}
  
  	/**
  	 * This TypeEvaluator is used to animate the BitmapDrawable back to its
  	 * final location when the user lifts his finger by modifying the
  	 * BitmapDrawable's bounds.
  	 */
  	private final static TypeEvaluator<Rect> sBoundEvaluator = new TypeEvaluator<Rect>() {
  		public Rect evaluate(float fraction, Rect startValue, Rect endValue) {
  			return new Rect(interpolate(startValue.left, endValue.left, fraction), interpolate(startValue.top, endValue.top, fraction), interpolate(startValue.right, endValue.right, fraction),
  					interpolate(startValue.bottom, endValue.bottom, fraction));
  		}
  
  		public int interpolate(int start, int end, float fraction) {
  			return (int) (start + fraction * (end - start));
  		}
  	};
  
  	/**
  	 *  Determines whether this listview is in a scrolling state invoked
  	 *  by the fact that the hover cell is out of the bounds of the listview;
  	 */
  	private void handleMobileCellScroll() {
  		mIsMobileScrolling = handleMobileCellScroll(mHoverCellCurrentBounds);
  	}
  
  	/**
  	 * This method is in charge of determining if the hover cell is above
  	 * or below the bounds of the listview. If so, the listview does an appropriate
  	 * upward or downward smooth scroll so as to reveal new items.
  	 */
  	public boolean handleMobileCellScroll(Rect r) {
  		int offset = computeVerticalScrollOffset();
  		int height = getHeight();
  		int extent = computeVerticalScrollExtent();
  		int range = computeVerticalScrollRange();
  		int hoverViewTop = r.top;
  		int hoverHeight = r.height();
  
  		if (hoverViewTop <= 0 && offset > 0) {
  			smoothScrollBy(-mSmoothScrollAmountAtEdge, 0);
  			return true;
  		}
  
  		if (hoverViewTop + hoverHeight >= height && (offset + extent) < range) {
  			smoothScrollBy(mSmoothScrollAmountAtEdge, 0);
  			return true;
  		}
  
  		return false;
  	}
  
  	public void setIsParentHorizontalScrollContainer(boolean isParentHorizontalScrollContainer) {
  		mIsParentHorizontalScrollContainer = (mResIdOfDynamicTouchChild == 0) ? isParentHorizontalScrollContainer : false;
  		;
  	}
  
  	public boolean isParentHorizontalScrollContainer() {
  		return mIsParentHorizontalScrollContainer;
  	}
  
  	public void setDynamicTouchChild(int childResId) {
  		mResIdOfDynamicTouchChild = childResId;
  		if (childResId != 0) {
  			setIsParentHorizontalScrollContainer(false);
  		}
  	}
  
  	/**
  	 * This scroll listener is added to the listview in order to handle cell swapping
  	 * when the cell is either at the top or bottom edge of the listview. If the hover
  	 * cell is at either edge of the listview, the listview will begin scrolling. As
  	 * scrolling takes place, the listview continuously checks if new cells became visible
  	 * and determines whether they are potential candidates for a cell swap.
  	 */
  	private OnScrollListener mScrollListener = new OnScrollListener() {
  
  		private int mPreviousFirstVisibleItem = -1;
  		private int mPreviousVisibleItemCount = -1;
  		private int mCurrentFirstVisibleItem;
  		private int mCurrentVisibleItemCount;
  		private int mCurrentScrollState;
  
  		public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
  			mCurrentFirstVisibleItem = firstVisibleItem;
  			mCurrentVisibleItemCount = visibleItemCount;
  
  			mPreviousFirstVisibleItem = (mPreviousFirstVisibleItem == -1) ? mCurrentFirstVisibleItem : mPreviousFirstVisibleItem;
  			mPreviousVisibleItemCount = (mPreviousVisibleItemCount == -1) ? mCurrentVisibleItemCount : mPreviousVisibleItemCount;
  
  			checkAndHandleFirstVisibleCellChange();
  			checkAndHandleLastVisibleCellChange();
  
  			mPreviousFirstVisibleItem = mCurrentFirstVisibleItem;
  			mPreviousVisibleItemCount = mCurrentVisibleItemCount;
  		}
  
  		@Override
  		public void onScrollStateChanged(AbsListView view, int scrollState) {
  			mCurrentScrollState = scrollState;
  			mScrollState = scrollState;
  			isScrollCompleted();
  		}
  
  		/**
  		 * This method is in charge of invoking 1 of 2 actions. Firstly, if the listview
  		 * is in a state of scrolling invoked by the hover cell being outside the bounds
  		 * of the listview, then this scrolling event is continued. Secondly, if the hover
  		 * cell has already been released, this invokes the animation for the hover cell
  		 * to return to its correct position after the listview has entered an idle scroll
  		 * state.
  		 */
  		private void isScrollCompleted() {
  			if (mCurrentVisibleItemCount > 0 && mCurrentScrollState == SCROLL_STATE_IDLE) {
  				if (mCellIsMobile && mIsMobileScrolling) {
  					handleMobileCellScroll();
  				} else if (mIsWaitingForScrollFinish) {
  					touchEventsEnded();
  				}
  			}
  		}
  
  		/**
  		 * Determines if the listview scrolled up enough to reveal a new cell at the
  		 * top of the list. If so, then the appropriate parameters are updated.
  		 */
  		public void checkAndHandleFirstVisibleCellChange() {
  			if (mCurrentFirstVisibleItem != mPreviousFirstVisibleItem) {
  				if (mCellIsMobile && mMobileItemId != INVALID_ID) {
  					updateNeighborViewsForID(mMobileItemId);
  					handleCellSwitch();
  				}
  			}
  		}
  
  		/**
  		 * Determines if the listview scrolled down enough to reveal a new cell at the
  		 * bottom of the list. If so, then the appropriate parameters are updated.
  		 */
  		public void checkAndHandleLastVisibleCellChange() {
  			int currentLastVisibleItem = mCurrentFirstVisibleItem + mCurrentVisibleItemCount;
  			int previousLastVisibleItem = mPreviousFirstVisibleItem + mPreviousVisibleItemCount;
  			if (currentLastVisibleItem != previousLastVisibleItem) {
  				if (mCellIsMobile && mMobileItemId != INVALID_ID) {
  					updateNeighborViewsForID(mMobileItemId);
  					handleCellSwitch();
  				}
  			}
  		}
  	};
  
  	/**
  	 * Interface, usually implemented by a {@link com.haarman.listviewanimations.BaseAdapterDecorator},
  	 * that indicates that it can swap the visual position of two list items.
  	 *
  	 * @author Anton Spaans on 9/11/13.
  	 */
  	public interface Swappable {
  
  		/**
  		 * Swaps the item on the first adapter position with the item on the second adapter position.
  		 * Be sure to call {@link android.widget.BaseAdapter#notifyDataSetChanged()} if appropriate.
  		 *
  		 * @param positionOne First adapter position.
  		 * @param positionTwo Second adapter position.
  		 */
  		public void swapItems(int positionOne, int positionTwo);
  	}
  }