package jp.sample;

import android.content.Context;
import android.database.DataSetObserver;
import android.os.Handler;
import android.os.Parcelable;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.util.SparseArray;
import android.view.ContextMenu;
import android.view.SoundEffectConstants;
import android.view.View;
import android.view.ViewDebug;
import android.view.ViewGroup;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.Adapter;

/**
 * <a href="http://beefsalt.blog79.fc2.com/">主にAndroid</a>
 * <br/>
 * <a href="http://www.apache.org/licenses/LICENSE-2.0">http://www.apache.org/licenses/LICENSE-2.0</a>
 * @author beefsalt
 *
 */
public abstract class VerticalGalleryAdapterView<T extends Adapter> extends
		ViewGroup {

	/**
	 * The item view type returned by {@link Adapter#getItemViewType(int)} when
	 * the adapter does not want the item's view recycled.
	 */
	public static final int ITEM_VIEW_TYPE_IGNORE = -1;

	/**
	 * The item view type returned by {@link Adapter#getItemViewType(int)} when
	 * the item is a header or footer.
	 */
	public static final int ITEM_VIEW_TYPE_HEADER_OR_FOOTER = -2;

	/**
	 * The position of the first child displayed
	 */
	@ViewDebug.ExportedProperty
	int mFirstPosition = 0;

	/**
	 * The offset in pixels from the top of the AdapterView to the top
	 * of the view to select during the next layout.
	 */
	int mSpecificTop;

	/**
	 * Position from which to start looking for mSyncRowId
	 */
	int mSyncPosition;

	/**
	 * Row id to look for when data has changed
	 */
	long mSyncRowId = INVALID_ROW_ID;

	/**
	 * Height of the view when mSyncPosition and mSyncRowId where set
	 */
	long mSyncHeight;

	/**
	 * True if we need to sync to mSyncRowId
	 */
	boolean mNeedSync = false;

	/**
	 * Indicates whether to sync based on the selection or position. Possible
	 * values are {@link #SYNC_SELECTED_POSITION} or
	 * {@link #SYNC_FIRST_POSITION}.
	 */
	int mSyncMode;

	/**
	 * Our height after the last layout
	 */
	private int mLayoutHeight;

	/**
	 * Sync based on the selected child
	 */
	static final int SYNC_SELECTED_POSITION = 0;

	/**
	 * Sync based on the first child displayed
	 */
	static final int SYNC_FIRST_POSITION = 1;

	/**
	 * Maximum amount of time to spend in {@link #findSyncPosition()}
	 */
	static final int SYNC_MAX_DURATION_MILLIS = 100;

	/**
	 * Indicates that this view is currently being laid out.
	 */
	boolean mInLayout = false;

	/**
	 * The listener that receives notifications when an item is selected.
	 */
	OnItemSelectedListener mOnItemSelectedListener;

	/**
	 * The listener that receives notifications when an item is clicked.
	 */
	OnItemClickListener mOnItemClickListener;

	/**
	 * The listener that receives notifications when an item is long clicked.
	 */
	OnItemLongClickListener mOnItemLongClickListener;

	/**
	 * True if the data has changed since the last layout
	 */
	boolean mDataChanged;

	/**
	 * The position within the adapter's data set of the item to select
	 * during the next layout.
	 */
	@ViewDebug.ExportedProperty
	int mNextSelectedPosition = INVALID_POSITION;

	/**
	 * The item id of the item to select during the next layout.
	 */
	long mNextSelectedRowId = INVALID_ROW_ID;

	/**
	 * The position within the adapter's data set of the currently selected
	 * item.
	 */
	@ViewDebug.ExportedProperty
	int mSelectedPosition = INVALID_POSITION;

	/**
	 * The item id of the currently selected item.
	 */
	long mSelectedRowId = INVALID_ROW_ID;

	/**
	 * View to show if there are no items to show.
	 */
	View mEmptyView;

	/**
	 * The number of items in the current adapter.
	 */
	@ViewDebug.ExportedProperty
	int mItemCount;

	/**
	 * The number of items in the adapter before a data changed event occured.
	 */
	int mOldItemCount;

	/**
	 * Represents an invalid position. All valid positions are in the range 0 to
	 * 1 less than the
	 * number of items in the current adapter.
	 */
	public static final int INVALID_POSITION = -1;

	/**
	 * Represents an empty or invalid row id
	 */
	public static final long INVALID_ROW_ID = Long.MIN_VALUE;

	/**
	 * The last selected position we used when notifying
	 */
	int mOldSelectedPosition = INVALID_POSITION;

	/**
	 * The id of the last selected position we used when notifying
	 */
	long mOldSelectedRowId = INVALID_ROW_ID;

	/**
	 * Indicates what focusable state is requested when calling setFocusable().
	 * In addition to this, this view has other criteria for actually
	 * determining the focusable state (such as whether its empty or the text
	 * filter is shown).
	 *
	 * @see #setFocusable(boolean)
	 * @see #checkFocus()
	 */
	private boolean mDesiredFocusableState;
	private boolean mDesiredFocusableInTouchModeState;

	private SelectionNotifier mSelectionNotifier;
	/**
	 * When set to true, calls to requestLayout() will not propagate up the
	 * parent hierarchy.
	 * This is used to layout the children during a layout pass.
	 */
	boolean mBlockLayoutRequests = false;

	public VerticalGalleryAdapterView(Context context) {
		super(context);
	}

	public VerticalGalleryAdapterView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public VerticalGalleryAdapterView(Context context, AttributeSet attrs,
			int defStyle) {
		super(context, attrs, defStyle);
	}

	/**
	 * Interface definition for a callback to be invoked when an item in this
	 * AdapterView has been clicked.
	 */
	public interface OnItemClickListener {

		/**
		 * Callback method to be invoked when an item in this AdapterView has
		 * been clicked.
		 * <p>
		 * Implementers can call getItemAtPosition(position) if they need to
		 * access the data associated with the selected item.
		 *
		 * @param parent
		 *            The AdapterView where the click happened.
		 * @param view
		 *            The view within the AdapterView that was clicked (this
		 *            will be a view provided by the adapter)
		 * @param position
		 *            The position of the view in the adapter.
		 * @param id
		 *            The row id of the item that was clicked.
		 */
		void onItemClick(VerticalGalleryAdapterView<?> parent, View view,
				int position, long id);

	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has
	 * been clicked.
	 *
	 * @param listener
	 *            The callback that will be invoked.
	 */
	public void setOnItemClickListener(OnItemClickListener listener) {
		mOnItemClickListener = listener;
	}

	/**
	 * @return The callback to be invoked with an item in this AdapterView has
	 *         been clicked, or null id no callback has been set.
	 */
	public final OnItemClickListener getOnItemClickListener() {
		return mOnItemClickListener;
	}

	/**
	 * Call the OnItemClickListener, if it is defined.
	 *
	 * @param view
	 *            The view within the AdapterView that was clicked.
	 * @param position
	 *            The position of the view in the adapter.
	 * @param id
	 *            The row id of the item that was clicked.
	 * @return True if there was an assigned OnItemClickListener that was
	 *         called, false otherwise is returned.
	 */
	public boolean performItemClick(View view, int position, long id) {
		if (mOnItemClickListener != null) {
			playSoundEffect(SoundEffectConstants.CLICK);
			mOnItemClickListener.onItemClick(this, view, position, id);
			return true;
		}

		return false;
	}

	/**
	 * Interface definition for a callback to be invoked when an item in this
	 * view has been clicked and held.
	 */
	public interface OnItemLongClickListener {
		/**
		 * Callback method to be invoked when an item in this view has been
		 * clicked and held.
		 *
		 * Implementers can call getItemAtPosition(position) if they need to
		 * access
		 * the data associated with the selected item.
		 *
		 * @param coverFlow
		 *            The AbsListView where the click happened
		 * @param view
		 *            The view within the AbsListView that was clicked
		 * @param position
		 *            The position of the view in the list
		 * @param id
		 *            The row id of the item that was clicked
		 *
		 * @return true if the callback consumed the long click, false otherwise
		 */
		boolean onItemLongClick(VerticalGallery verticalGallery, View view,
				int position, long id);
	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has
	 * been clicked and held
	 *
	 * @param listener
	 *            The callback that will run
	 */
	public void setOnItemLongClickListener(OnItemLongClickListener listener) {
		if (!isLongClickable()) {
			setLongClickable(true);
		}
		mOnItemLongClickListener = listener;
	}

	/**
	 * @return The callback to be invoked with an item in this AdapterView has
	 *         been clicked and held, or null id no callback as been set.
	 */
	public final OnItemLongClickListener getOnItemLongClickListener() {
		return mOnItemLongClickListener;
	}

	/**
	 * Interface definition for a callback to be invoked when
	 * an item in this view has been selected.
	 */
	public interface OnItemSelectedListener {
		/**
		 * Callback method to be invoked when an item in this view has been
		 * selected.
		 *
		 * Impelmenters can call getItemAtPosition(position) if they need to
		 * access the
		 * data associated with the selected item.
		 *
		 * @param parent
		 *            The AdapterView where the selection happened
		 * @param view
		 *            The view within the AdapterView that was clicked
		 * @param position
		 *            The position of the view in the adapter
		 * @param id
		 *            The row id of the item that is selected
		 */
		void onItemSelected(VerticalGalleryAdapterView<?> parent, View view,
				int position, long id);

		/**
		 * Callback method to be invoked when the selection disappears from this
		 * view. The selection can disappear for instance when touch is
		 * activated
		 * or when the adapter becomes empty.
		 *
		 * @param parent
		 *            The AdapterView that now contains no selected item.
		 */
		void onNothingSelected(VerticalGalleryAdapterView<?> parent);
	}

	/**
	 * Register a callback to be invoked when an item in this AdapterView has
	 * been selected.
	 *
	 * @param listener
	 *            The callback that will run
	 */
	public void setOnItemSelectedListener(OnItemSelectedListener listener) {
		mOnItemSelectedListener = listener;
	}

	public final OnItemSelectedListener getOnItemSelectedListener() {
		return mOnItemSelectedListener;
	}

	/**
	 * Extra menu information provided to the
	 * {@link android.view.View.OnCreateContextMenuListener#onCreateContextMenu(ContextMenu, View, ContextMenuInfo) }
	 * callback when a context menu is brought up for this AdapterView.
	 *
	 */
	public static class AdapterContextMenuInfo implements
			ContextMenu.ContextMenuInfo {

		public AdapterContextMenuInfo(View targetView, int position, long id) {
			this.targetView = targetView;
			this.position = position;
			this.id = id;
		}

		/**
		 * The child view for which the context menu is being displayed. This
		 * will be one of the children of this AdapterView.
		 */
		public View targetView;

		/**
		 * The position in the adapter for which the context menu is being
		 * displayed.
		 */
		public int position;

		/**
		 * The row id of the item for which the context menu is being displayed.
		 */
		public long id;
	}

	/**
	 * Returns the adapter currently associated with this widget.
	 *
	 * @return The adapter used to provide this view's content.
	 */
	public abstract T getAdapter();

	/**
	 * Sets the adapter that provides the data and the views to represent the
	 * data
	 * in this widget.
	 *
	 * @param adapter
	 *            The adapter to use to create this view's content.
	 */
	public abstract void setAdapter(T adapter);

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param child
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void addView(View child) {
		throw new UnsupportedOperationException(
				"addView(View) is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param child
	 *            Ignored.
	 * @param index
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void addView(View child, int index) {
		throw new UnsupportedOperationException(
				"addView(View, int) is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param child
	 *            Ignored.
	 * @param params
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void addView(View child, LayoutParams params) {
		throw new UnsupportedOperationException("addView(View, LayoutParams) "
				+ "is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param child
	 *            Ignored.
	 * @param index
	 *            Ignored.
	 * @param params
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void addView(View child, int index, LayoutParams params) {
		throw new UnsupportedOperationException(
				"addView(View, int, LayoutParams) "
						+ "is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param child
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void removeView(View child) {
		throw new UnsupportedOperationException(
				"removeView(View) is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @param index
	 *            Ignored.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void removeViewAt(int index) {
		throw new UnsupportedOperationException(
				"removeViewAt(int) is not supported in AdapterView");
	}

	/**
	 * This method is not supported and throws an UnsupportedOperationException
	 * when called.
	 *
	 * @throws UnsupportedOperationException
	 *             Every time this method is invoked.
	 */
	@Override
	public void removeAllViews() {
		throw new UnsupportedOperationException(
				"removeAllViews() is not supported in AdapterView");
	}

	@Override
	protected void onLayout(boolean changed, int left, int top, int right,
			int bottom) {
		mLayoutHeight = getHeight();
	}

	/**
	 * Return the position of the currently selected item within the adapter's
	 * data set
	 *
	 * @return int Position (starting at 0), or {@link #INVALID_POSITION} if
	 *         there is nothing selected.
	 */
	// @ViewDebug.CapturedViewProperty
	public int getSelectedItemPosition() {
		return mNextSelectedPosition;
	}

	/**
	 * @return The id corresponding to the currently selected item, or
	 *         {@link #INVALID_ROW_ID} if nothing is selected.
	 */
	// @ViewDebug.CapturedViewProperty
	public long getSelectedItemId() {
		return mNextSelectedRowId;
	}

	/**
	 * @return The view corresponding to the currently selected item, or null
	 *         if nothing is selected
	 */
	public abstract View getSelectedView();

	/**
	 * @return The data corresponding to the currently selected item, or
	 *         null if there is nothing selected.
	 */
	public Object getSelectedItem() {
		T adapter = getAdapter();
		int selection = getSelectedItemPosition();
		if (adapter != null && adapter.getCount() > 0 && selection >= 0) {
			return adapter.getItem(selection);
		} else {
			return null;
		}
	}

	/**
	 * @return The number of items owned by the Adapter associated with this
	 *         AdapterView. (This is the number of data items, which may be
	 *         larger than the number of visible view.)
	 */
	// @ViewDebug.CapturedViewProperty
	public int getCount() {
		return mItemCount;
	}

	/**
	 * Get the position within the adapter's data set for the view, where view
	 * is a an adapter item
	 * or a descendant of an adapter item.
	 *
	 * @param view
	 *            an adapter item, or a descendant of an adapter item. This must
	 *            be visible in this
	 *            AdapterView at the time of the call.
	 * @return the position within the adapter's data set of the view, or
	 *         {@link #INVALID_POSITION} if the view does not correspond to a
	 *         list item (or it is not currently visible).
	 */
	public int getPositionForView(View view) {
		View listItem = view;
		try {
			View v;
			while (!(v = (View) listItem.getParent()).equals(this)) {
				listItem = v;
			}
		} catch (ClassCastException e) {
			// We made it up to the window without find this list view
			return INVALID_POSITION;
		}

		// Search the children for the list item
		final int childCount = getChildCount();
		for (int i = 0; i < childCount; i++) {
			if (getChildAt(i).equals(listItem)) {
				return mFirstPosition + i;
			}
		}

		// Child not found!
		return INVALID_POSITION;
	}

	/**
	 * Returns the position within the adapter's data set for the first item
	 * displayed on screen.
	 *
	 * @return The position within the adapter's data set
	 */
	public int getFirstVisiblePosition() {
		return mFirstPosition;
	}

	/**
	 * Returns the position within the adapter's data set for the last item
	 * displayed on screen.
	 *
	 * @return The position within the adapter's data set
	 */
	public int getLastVisiblePosition() {
		return mFirstPosition + getChildCount() - 1;
	}

	/**
	 * Sets the currently selected item
	 *
	 * @param position
	 *            Index (starting at 0) of the data item to be selected.
	 */
	public abstract void setSelection(int position);

	/**
	 * Sets the view to show if the adapter is empty
	 */
	public void setEmptyView(View emptyView) {
		mEmptyView = emptyView;

		final T adapter = getAdapter();
		final boolean empty = ((adapter == null) || adapter.isEmpty());
		updateEmptyStatus(empty);
	}

	/**
	 * When the current adapter is empty, the AdapterView can display a special
	 * view
	 * call the empty view. The empty view is used to provide feedback to the
	 * user
	 * that no data is available in this AdapterView.
	 *
	 * @return The view to show if the adapter is empty.
	 */
	public View getEmptyView() {
		return mEmptyView;
	}

	/**
	 * Indicates whether this view is in filter mode. Filter mode can for
	 * instance
	 * be enabled by a user when typing on the keyboard.
	 *
	 * @return True if the view is in filter mode, false otherwise.
	 */
	boolean isInFilterMode() {
		return false;
	}

	@Override
	public void setFocusable(boolean focusable) {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;

		mDesiredFocusableState = focusable;
		if (!focusable) {
			mDesiredFocusableInTouchModeState = false;
		}

		super.setFocusable(focusable && (!empty || isInFilterMode()));
	}

	@Override
	public void setFocusableInTouchMode(boolean focusable) {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;

		mDesiredFocusableInTouchModeState = focusable;
		if (focusable) {
			mDesiredFocusableState = true;
		}

		super
				.setFocusableInTouchMode(focusable
						&& (!empty || isInFilterMode()));
	}

	void checkFocus() {
		final T adapter = getAdapter();
		final boolean empty = adapter == null || adapter.getCount() == 0;
		final boolean focusable = !empty || isInFilterMode();
		// The order in which we set focusable in touch mode/focusable may
		// matter
		// for the client, see View.setFocusableInTouchMode() comments for more
		// details
		super.setFocusableInTouchMode(focusable
				&& mDesiredFocusableInTouchModeState);
		super.setFocusable(focusable && mDesiredFocusableState);
		if (mEmptyView != null) {
			updateEmptyStatus((adapter == null) || adapter.isEmpty());
		}
	}

	/**
	 * Update the status of the list based on the empty parameter. If empty is
	 * true and
	 * we have an empty view, display it. In all the other cases, make sure that
	 * the listview
	 * is VISIBLE and that the empty view is GONE (if it's not null).
	 */
	private void updateEmptyStatus(boolean empty) {
		if (isInFilterMode()) {
			empty = false;
		}

		if (empty) {
			if (mEmptyView != null) {
				mEmptyView.setVisibility(View.VISIBLE);
				setVisibility(View.GONE);
			} else {
				// If the caller just removed our empty view, make sure the list
				// view is visible
				setVisibility(View.VISIBLE);
			}

			// We are now GONE, so pending layouts will not be dispatched.
			// Force one here to make sure that the state of the list matches
			// the state of the adapter.
			if (mDataChanged) {
				this.onLayout(false, getLeft(), getTop(), getRight(),
						getBottom());
			}
		} else {
			if (mEmptyView != null)
				mEmptyView.setVisibility(View.GONE);
			setVisibility(View.VISIBLE);
		}
	}

	/**
	 * Gets the data associated with the specified position in the list.
	 *
	 * @param position
	 *            Which data to get
	 * @return The data associated with the specified position in the list
	 */
	public Object getItemAtPosition(int position) {
		T adapter = getAdapter();
		return (adapter == null || position < 0) ? null : adapter
				.getItem(position);
	}

	public long getItemIdAtPosition(int position) {
		T adapter = getAdapter();
		return (adapter == null || position < 0) ? INVALID_ROW_ID : adapter
				.getItemId(position);
	}

	@Override
	public void setOnClickListener(OnClickListener l) {
		throw new RuntimeException(
				"Don't call setOnClickListener for an AdapterView. "
						+ "You probably want setOnItemClickListener instead");
	}

	/**
	 * Override to prevent freezing of any views created by the adapter.
	 */
	@Override
	protected void dispatchSaveInstanceState(SparseArray<Parcelable> container) {
		dispatchFreezeSelfOnly(container);
	}

	/**
	 * Override to prevent thawing of any views created by the adapter.
	 */
	@Override
	protected void dispatchRestoreInstanceState(
			SparseArray<Parcelable> container) {
		dispatchThawSelfOnly(container);
	}

	class AdapterDataSetObserver extends DataSetObserver {

		private Parcelable mInstanceState = null;

		@Override
		public void onChanged() {
			mDataChanged = true;
			mOldItemCount = mItemCount;
			mItemCount = getAdapter().getCount();

			// Detect the case where a cursor that was previously invalidated
			// has
			// been repopulated with new data.
			if (VerticalGalleryAdapterView.this.getAdapter().hasStableIds()
					&& mInstanceState != null && mOldItemCount == 0
					&& mItemCount > 0) {
				VerticalGalleryAdapterView.this
						.onRestoreInstanceState(mInstanceState);
				mInstanceState = null;
			} else {
				rememberSyncState();
			}
			checkFocus();
			requestLayout();
		}

		@Override
		public void onInvalidated() {
			mDataChanged = true;

			if (VerticalGalleryAdapterView.this.getAdapter().hasStableIds()) {
				// Remember the current state for the case where our hosting
				// activity is being
				// stopped and later restarted
				mInstanceState = VerticalGalleryAdapterView.this
						.onSaveInstanceState();
			}

			// Data is invalid so we should reset our state
			mOldItemCount = mItemCount;
			mItemCount = 0;
			mSelectedPosition = INVALID_POSITION;
			mSelectedRowId = INVALID_ROW_ID;
			mNextSelectedPosition = INVALID_POSITION;
			mNextSelectedRowId = INVALID_ROW_ID;
			mNeedSync = false;
			checkSelectionChanged();

			checkFocus();
			requestLayout();
		}

		public void clearSavedState() {
			mInstanceState = null;
		}
	}

	private class SelectionNotifier extends Handler implements Runnable {
		public void run() {
			if (mDataChanged) {
				// Data has changed between when this SelectionNotifier
				// was posted and now. We need to wait until the AdapterView
				// has been synched to the new data.
				post(this);
			} else {
				fireOnSelected();
			}
		}
	}

	void selectionChanged() {
		if (mOnItemSelectedListener != null) {
			if (mInLayout || mBlockLayoutRequests) {
				// If we are in a layout traversal, defer notification
				// by posting. This ensures that the view tree is
				// in a consistent state and is able to accomodate
				// new layout or invalidate requests.
				if (mSelectionNotifier == null) {
					mSelectionNotifier = new SelectionNotifier();
				}
				mSelectionNotifier.post(mSelectionNotifier);
			} else {
				fireOnSelected();
			}
		}
	}

	private void fireOnSelected() {
		if (mOnItemSelectedListener == null)
			return;

		int selection = this.getSelectedItemPosition();
		if (selection >= 0) {
			View v = getSelectedView();
			mOnItemSelectedListener.onItemSelected(this, v, selection,
					getAdapter().getItemId(selection));
		} else {
			mOnItemSelectedListener.onNothingSelected(this);
		}
	}

	@Override
	protected boolean canAnimate() {
		return super.canAnimate() && mItemCount > 0;
	}

	void handleDataChanged() {
		final int count = mItemCount;
		boolean found = false;

		if (count > 0) {

			int newPos;

			// Find the row we are supposed to sync to
			if (mNeedSync) {
				// Update this first, since setNextSelectedPositionInt inspects
				// it
				mNeedSync = false;

				// See if we can find a position in the new data with the same
				// id as the old selection
				newPos = findSyncPosition();
				if (newPos >= 0) {
					// Verify that new selection is selectable
					int selectablePos = lookForSelectablePosition(newPos, true);
					if (selectablePos == newPos) {
						// Same row id is selected
						setNextSelectedPositionInt(newPos);
						found = true;
					}
				}
			}
			if (!found) {
				// Try to use the same position if we can't find matching data
				newPos = getSelectedItemPosition();

				// Pin position to the available range
				if (newPos >= count) {
					newPos = count - 1;
				}
				if (newPos < 0) {
					newPos = 0;
				}

				// Make sure we select something selectable -- first look down
				int selectablePos = lookForSelectablePosition(newPos, true);
				if (selectablePos < 0) {
					// Looking down didn't work -- try looking up
					selectablePos = lookForSelectablePosition(newPos, false);
				}
				if (selectablePos >= 0) {
					setNextSelectedPositionInt(selectablePos);
					checkSelectionChanged();
					found = true;
				}
			}
		}
		if (!found) {
			// Nothing is selected
			mSelectedPosition = INVALID_POSITION;
			mSelectedRowId = INVALID_ROW_ID;
			mNextSelectedPosition = INVALID_POSITION;
			mNextSelectedRowId = INVALID_ROW_ID;
			mNeedSync = false;
			checkSelectionChanged();
		}
	}

	void checkSelectionChanged() {
		if ((mSelectedPosition != mOldSelectedPosition)
				|| (mSelectedRowId != mOldSelectedRowId)) {
			selectionChanged();
			mOldSelectedPosition = mSelectedPosition;
			mOldSelectedRowId = mSelectedRowId;
		}
	}

	/**
	 * Searches the adapter for a position matching mSyncRowId. The search
	 * starts at mSyncPosition
	 * and then alternates between moving up and moving down until 1) we find
	 * the right position, or
	 * 2) we run out of time, or 3) we have looked at every position
	 *
	 * @return Position of the row that matches mSyncRowId, or
	 *         {@link #INVALID_POSITION} if it can't
	 *         be found
	 */
	int findSyncPosition() {
		int count = mItemCount;

		if (count == 0) {
			return INVALID_POSITION;
		}

		long idToMatch = mSyncRowId;
		int seed = mSyncPosition;

		// If there isn't a selection don't hunt for it
		if (idToMatch == INVALID_ROW_ID) {
			return INVALID_POSITION;
		}

		// Pin seed to reasonable values
		seed = Math.max(0, seed);
		seed = Math.min(count - 1, seed);

		long endTime = SystemClock.uptimeMillis() + SYNC_MAX_DURATION_MILLIS;

		long rowId;

		// first position scanned so far
		int first = seed;

		// last position scanned so far
		int last = seed;

		// True if we should move down on the next iteration
		boolean next = false;

		// True when we have looked at the first item in the data
		boolean hitFirst;

		// True when we have looked at the last item in the data
		boolean hitLast;

		// Get the item ID locally (instead of getItemIdAtPosition), so
		// we need the adapter
		T adapter = getAdapter();
		if (adapter == null) {
			return INVALID_POSITION;
		}

		while (SystemClock.uptimeMillis() <= endTime) {
			rowId = adapter.getItemId(seed);
			if (rowId == idToMatch) {
				// Found it!
				return seed;
			}

			hitLast = last == count - 1;
			hitFirst = first == 0;

			if (hitLast && hitFirst) {
				// Looked at everything
				break;
			}

			if (hitFirst || (next && !hitLast)) {
				// Either we hit the top, or we are trying to move down
				last++;
				seed = last;
				// Try going up next time
				next = false;
			} else if (hitLast || (!next && !hitFirst)) {
				// Either we hit the bottom, or we are trying to move up
				first--;
				seed = first;
				// Try going down next time
				next = true;
			}

		}

		return INVALID_POSITION;
	}

	/**
	 * Find a position that can be selected (i.e., is not a separator).
	 *
	 * @param position
	 *            The starting position to look at.
	 * @param lookDown
	 *            Whether to look down for other positions.
	 * @return The next selectable position starting at position and then
	 *         searching either up or
	 *         down. Returns {@link #INVALID_POSITION} if nothing can be found.
	 */
	int lookForSelectablePosition(int position, boolean lookDown) {
		return position;
	}

	/**
	 * Utility to keep mSelectedPosition and mSelectedRowId in sync
	 *
	 * @param position
	 *            Our current position
	 */
	void setSelectedPositionInt(int position) {
		mSelectedPosition = position;
		mSelectedRowId = getItemIdAtPosition(position);
	}

	/**
	 * Utility to keep mNextSelectedPosition and mNextSelectedRowId in sync
	 *
	 * @param position
	 *            Intended value for mSelectedPosition the next time we go
	 *            through layout
	 */
	void setNextSelectedPositionInt(int position) {
		mNextSelectedPosition = position;
		mNextSelectedRowId = getItemIdAtPosition(position);
		// If we are trying to sync to the selection, update that too
		if (mNeedSync && mSyncMode == SYNC_SELECTED_POSITION && position >= 0) {
			mSyncPosition = position;
			mSyncRowId = mNextSelectedRowId;
		}
	}

	/**
	 * Remember enough information to restore the screen state when the data has
	 * changed.
	 *
	 */
	void rememberSyncState() {
		if (getChildCount() > 0) {
			mNeedSync = true;
			mSyncHeight = mLayoutHeight;
			if (mSelectedPosition >= 0) {
				// Sync the selection state
				View v = getChildAt(mSelectedPosition - mFirstPosition);
				mSyncRowId = mNextSelectedRowId;
				mSyncPosition = mNextSelectedPosition;
				if (v != null) {
					mSpecificTop = v.getTop();
				}
				mSyncMode = SYNC_SELECTED_POSITION;
			} else {
				// Sync the based on the offset of the first view
				View v = getChildAt(0);
				T adapter = getAdapter();
				if (mFirstPosition >= 0 && mFirstPosition < adapter.getCount()) {
					mSyncRowId = adapter.getItemId(mFirstPosition);
				} else {
					mSyncRowId = NO_ID;
				}
				mSyncPosition = mFirstPosition;
				if (v != null) {
					mSpecificTop = v.getTop();
				}
				mSyncMode = SYNC_FIRST_POSITION;
			}
		}
	}
}