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/*
* Copyright (C) 2006 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 android.widget;
import com.android.internal.R;
import com.android.internal.util.Predicate;
import com.google.android.collect.Lists;
import android.content.Context;
import android.content.Intent;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.SparseBooleanArray;
import android.view.FocusFinder;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.View;
import android.view.ViewDebug;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.widget.RemoteViews.RemoteView;
import java.util.ArrayList;
/*
* Implementation Notes:
*
* Some terminology:
*
* index - index of the items that are currently visible
* position - index of the items in the cursor
*/
/**
* A view that shows items in a vertically scrolling list. The items
* come from the {@link ListAdapter} associated with this view.
*
* <p>See the <a href="{@docRoot}resources/tutorials/views/hello-listview.html">List View
* tutorial</a>.</p>
*
* @attr ref android.R.styleable#ListView_entries
* @attr ref android.R.styleable#ListView_divider
* @attr ref android.R.styleable#ListView_dividerHeight
* @attr ref android.R.styleable#ListView_headerDividersEnabled
* @attr ref android.R.styleable#ListView_footerDividersEnabled
*/
@RemoteView
public class ListView extends AbsListView {
/**
* Used to indicate a no preference for a position type.
*/
static final int NO_POSITION = -1;
/**
* When arrow scrolling, ListView will never scroll more than this factor
* times the height of the list.
*/
private static final float MAX_SCROLL_FACTOR = 0.33f;
/**
* When arrow scrolling, need a certain amount of pixels to preview next
* items. This is usually the fading edge, but if that is small enough,
* we want to make sure we preview at least this many pixels.
*/
private static final int MIN_SCROLL_PREVIEW_PIXELS = 2;
/**
* A class that represents a fixed view in a list, for example a header at the top
* or a footer at the bottom.
*/
public class FixedViewInfo {
/** The view to add to the list */
public View view;
/** The data backing the view. This is returned from {@link ListAdapter#getItem(int)}. */
public Object data;
/** <code>true</code> if the fixed view should be selectable in the list */
public boolean isSelectable;
}
private ArrayList<FixedViewInfo> mHeaderViewInfos = Lists.newArrayList();
private ArrayList<FixedViewInfo> mFooterViewInfos = Lists.newArrayList();
Drawable mDivider;
int mDividerHeight;
Drawable mOverScrollHeader;
Drawable mOverScrollFooter;
private boolean mIsCacheColorOpaque;
private boolean mDividerIsOpaque;
private boolean mHeaderDividersEnabled;
private boolean mFooterDividersEnabled;
private boolean mAreAllItemsSelectable = true;
private boolean mItemsCanFocus = false;
// used for temporary calculations.
private final Rect mTempRect = new Rect();
private Paint mDividerPaint;
// the single allocated result per list view; kinda cheesey but avoids
// allocating these thingies too often.
private final ArrowScrollFocusResult mArrowScrollFocusResult = new ArrowScrollFocusResult();
// Keeps focused children visible through resizes
private FocusSelector mFocusSelector;
public ListView(Context context) {
this(context, null);
}
public ListView(Context context, AttributeSet attrs) {
this(context, attrs, com.android.internal.R.attr.listViewStyle);
}
public ListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.obtainStyledAttributes(attrs,
com.android.internal.R.styleable.ListView, defStyle, 0);
CharSequence[] entries = a.getTextArray(
com.android.internal.R.styleable.ListView_entries);
if (entries != null) {
setAdapter(new ArrayAdapter<CharSequence>(context,
com.android.internal.R.layout.simple_list_item_1, entries));
}
final Drawable d = a.getDrawable(com.android.internal.R.styleable.ListView_divider);
if (d != null) {
// If a divider is specified use its intrinsic height for divider height
setDivider(d);
}
final Drawable osHeader = a.getDrawable(
com.android.internal.R.styleable.ListView_overScrollHeader);
if (osHeader != null) {
setOverscrollHeader(osHeader);
}
final Drawable osFooter = a.getDrawable(
com.android.internal.R.styleable.ListView_overScrollFooter);
if (osFooter != null) {
setOverscrollFooter(osFooter);
}
// Use the height specified, zero being the default
final int dividerHeight = a.getDimensionPixelSize(
com.android.internal.R.styleable.ListView_dividerHeight, 0);
if (dividerHeight != 0) {
setDividerHeight(dividerHeight);
}
mHeaderDividersEnabled = a.getBoolean(R.styleable.ListView_headerDividersEnabled, true);
mFooterDividersEnabled = a.getBoolean(R.styleable.ListView_footerDividersEnabled, true);
a.recycle();
}
/**
* @return The maximum amount a list view will scroll in response to
* an arrow event.
*/
public int getMaxScrollAmount() {
return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop));
}
/**
* Make sure views are touching the top or bottom edge, as appropriate for
* our gravity
*/
private void adjustViewsUpOrDown() {
final int childCount = getChildCount();
int delta;
if (childCount > 0) {
View child;
if (!mStackFromBottom) {
// Uh-oh -- we came up short. Slide all views up to make them
// align with the top
child = getChildAt(0);
delta = child.getTop() - mListPadding.top;
if (mFirstPosition != 0) {
// It's OK to have some space above the first item if it is
// part of the vertical spacing
delta -= mDividerHeight;
}
if (delta < 0) {
// We only are looking to see if we are too low, not too high
delta = 0;
}
} else {
// we are too high, slide all views down to align with bottom
child = getChildAt(childCount - 1);
delta = child.getBottom() - (getHeight() - mListPadding.bottom);
if (mFirstPosition + childCount < mItemCount) {
// It's OK to have some space below the last item if it is
// part of the vertical spacing
delta += mDividerHeight;
}
if (delta > 0) {
delta = 0;
}
}
if (delta != 0) {
offsetChildrenTopAndBottom(-delta);
}
}
}
/**
* Add a fixed view to appear at the top of the list. If addHeaderView is
* called more than once, the views will appear in the order they were
* added. Views added using this call can take focus if they want.
* <p>
* NOTE: Call this before calling setAdapter. This is so ListView can wrap
* the supplied cursor with one that will also account for header and footer
* views.
*
* @param v The view to add.
* @param data Data to associate with this view
* @param isSelectable whether the item is selectable
*/
public void addHeaderView(View v, Object data, boolean isSelectable) {
if (mAdapter != null && ! (mAdapter instanceof HeaderViewListAdapter)) {
throw new IllegalStateException(
"Cannot add header view to list -- setAdapter has already been called.");
}
FixedViewInfo info = new FixedViewInfo();
info.view = v;
info.data = data;
info.isSelectable = isSelectable;
mHeaderViewInfos.add(info);
// in the case of re-adding a header view, or adding one later on,
// we need to notify the observer
if (mAdapter != null && mDataSetObserver != null) {
mDataSetObserver.onChanged();
}
}
/**
* Add a fixed view to appear at the top of the list. If addHeaderView is
* called more than once, the views will appear in the order they were
* added. Views added using this call can take focus if they want.
* <p>
* NOTE: Call this before calling setAdapter. This is so ListView can wrap
* the supplied cursor with one that will also account for header and footer
* views.
*
* @param v The view to add.
*/
public void addHeaderView(View v) {
addHeaderView(v, null, true);
}
@Override
public int getHeaderViewsCount() {
return mHeaderViewInfos.size();
}
/**
* Removes a previously-added header view.
*
* @param v The view to remove
* @return true if the view was removed, false if the view was not a header
* view
*/
public boolean removeHeaderView(View v) {
if (mHeaderViewInfos.size() > 0) {
boolean result = false;
if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeHeader(v)) {
if (mDataSetObserver != null) {
mDataSetObserver.onChanged();
}
result = true;
}
removeFixedViewInfo(v, mHeaderViewInfos);
return result;
}
return false;
}
private void removeFixedViewInfo(View v, ArrayList<FixedViewInfo> where) {
int len = where.size();
for (int i = 0; i < len; ++i) {
FixedViewInfo info = where.get(i);
if (info.view == v) {
where.remove(i);
break;
}
}
}
/**
* Add a fixed view to appear at the bottom of the list. If addFooterView is
* called more than once, the views will appear in the order they were
* added. Views added using this call can take focus if they want.
* <p>
* NOTE: Call this before calling setAdapter. This is so ListView can wrap
* the supplied cursor with one that will also account for header and footer
* views.
*
* @param v The view to add.
* @param data Data to associate with this view
* @param isSelectable true if the footer view can be selected
*/
public void addFooterView(View v, Object data, boolean isSelectable) {
// NOTE: do not enforce the adapter being null here, since unlike in
// addHeaderView, it was never enforced here, and so existing apps are
// relying on being able to add a footer and then calling setAdapter to
// force creation of the HeaderViewListAdapter wrapper
FixedViewInfo info = new FixedViewInfo();
info.view = v;
info.data = data;
info.isSelectable = isSelectable;
mFooterViewInfos.add(info);
// in the case of re-adding a footer view, or adding one later on,
// we need to notify the observer
if (mAdapter != null && mDataSetObserver != null) {
mDataSetObserver.onChanged();
}
}
/**
* Add a fixed view to appear at the bottom of the list. If addFooterView is called more
* than once, the views will appear in the order they were added. Views added using
* this call can take focus if they want.
* <p>NOTE: Call this before calling setAdapter. This is so ListView can wrap the supplied
* cursor with one that will also account for header and footer views.
*
*
* @param v The view to add.
*/
public void addFooterView(View v) {
addFooterView(v, null, true);
}
@Override
public int getFooterViewsCount() {
return mFooterViewInfos.size();
}
/**
* Removes a previously-added footer view.
*
* @param v The view to remove
* @return
* true if the view was removed, false if the view was not a footer view
*/
public boolean removeFooterView(View v) {
if (mFooterViewInfos.size() > 0) {
boolean result = false;
if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeFooter(v)) {
if (mDataSetObserver != null) {
mDataSetObserver.onChanged();
}
result = true;
}
removeFixedViewInfo(v, mFooterViewInfos);
return result;
}
return false;
}
/**
* Returns the adapter currently in use in this ListView. The returned adapter
* might not be the same adapter passed to {@link #setAdapter(ListAdapter)} but
* might be a {@link WrapperListAdapter}.
*
* @return The adapter currently used to display data in this ListView.
*
* @see #setAdapter(ListAdapter)
*/
@Override
public ListAdapter getAdapter() {
return mAdapter;
}
/**
* Sets up this AbsListView to use a remote views adapter which connects to a RemoteViewsService
* through the specified intent.
* @param intent the intent used to identify the RemoteViewsService for the adapter to connect to.
*/
@android.view.RemotableViewMethod
public void setRemoteViewsAdapter(Intent intent) {
super.setRemoteViewsAdapter(intent);
}
/**
* Sets the data behind this ListView.
*
* The adapter passed to this method may be wrapped by a {@link WrapperListAdapter},
* depending on the ListView features currently in use. For instance, adding
* headers and/or footers will cause the adapter to be wrapped.
*
* @param adapter The ListAdapter which is responsible for maintaining the
* data backing this list and for producing a view to represent an
* item in that data set.
*
* @see #getAdapter()
*/
@Override
public void setAdapter(ListAdapter adapter) {
if (mAdapter != null && mDataSetObserver != null) {
mAdapter.unregisterDataSetObserver(mDataSetObserver);
}
resetList();
mRecycler.clear();
if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) {
mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, adapter);
} else {
mAdapter = adapter;
}
mOldSelectedPosition = INVALID_POSITION;
mOldSelectedRowId = INVALID_ROW_ID;
// AbsListView#setAdapter will update choice mode states.
super.setAdapter(adapter);
if (mAdapter != null) {
mAreAllItemsSelectable = mAdapter.areAllItemsEnabled();
mOldItemCount = mItemCount;
mItemCount = mAdapter.getCount();
checkFocus();
mDataSetObserver = new AdapterDataSetObserver();
mAdapter.registerDataSetObserver(mDataSetObserver);
mRecycler.setViewTypeCount(mAdapter.getViewTypeCount());
int position;
if (mStackFromBottom) {
position = lookForSelectablePosition(mItemCount - 1, false);
} else {
position = lookForSelectablePosition(0, true);
}
setSelectedPositionInt(position);
setNextSelectedPositionInt(position);
if (mItemCount == 0) {
// Nothing selected
checkSelectionChanged();
}
} else {
mAreAllItemsSelectable = true;
checkFocus();
// Nothing selected
checkSelectionChanged();
}
requestLayout();
}
/**
* The list is empty. Clear everything out.
*/
@Override
void resetList() {
// The parent's resetList() will remove all views from the layout so we need to
// cleanup the state of our footers and headers
clearRecycledState(mHeaderViewInfos);
clearRecycledState(mFooterViewInfos);
super.resetList();
mLayoutMode = LAYOUT_NORMAL;
}
private void clearRecycledState(ArrayList<FixedViewInfo> infos) {
if (infos != null) {
final int count = infos.size();
for (int i = 0; i < count; i++) {
final View child = infos.get(i).view;
final LayoutParams p = (LayoutParams) child.getLayoutParams();
if (p != null) {
p.recycledHeaderFooter = false;
}
}
}
}
/**
* @return Whether the list needs to show the top fading edge
*/
private boolean showingTopFadingEdge() {
final int listTop = mScrollY + mListPadding.top;
return (mFirstPosition > 0) || (getChildAt(0).getTop() > listTop);
}
/**
* @return Whether the list needs to show the bottom fading edge
*/
private boolean showingBottomFadingEdge() {
final int childCount = getChildCount();
final int bottomOfBottomChild = getChildAt(childCount - 1).getBottom();
final int lastVisiblePosition = mFirstPosition + childCount - 1;
final int listBottom = mScrollY + getHeight() - mListPadding.bottom;
return (lastVisiblePosition < mItemCount - 1)
|| (bottomOfBottomChild < listBottom);
}
@Override
public boolean requestChildRectangleOnScreen(View child, Rect rect, boolean immediate) {
int rectTopWithinChild = rect.top;
// offset so rect is in coordinates of the this view
rect.offset(child.getLeft(), child.getTop());
rect.offset(-child.getScrollX(), -child.getScrollY());
final int height = getHeight();
int listUnfadedTop = getScrollY();
int listUnfadedBottom = listUnfadedTop + height;
final int fadingEdge = getVerticalFadingEdgeLength();
if (showingTopFadingEdge()) {
// leave room for top fading edge as long as rect isn't at very top
if ((mSelectedPosition > 0) || (rectTopWithinChild > fadingEdge)) {
listUnfadedTop += fadingEdge;
}
}
int childCount = getChildCount();
int bottomOfBottomChild = getChildAt(childCount - 1).getBottom();
if (showingBottomFadingEdge()) {
// leave room for bottom fading edge as long as rect isn't at very bottom
if ((mSelectedPosition < mItemCount - 1)
|| (rect.bottom < (bottomOfBottomChild - fadingEdge))) {
listUnfadedBottom -= fadingEdge;
}
}
int scrollYDelta = 0;
if (rect.bottom > listUnfadedBottom && rect.top > listUnfadedTop) {
// need to MOVE DOWN to get it in view: move down just enough so
// that the entire rectangle is in view (or at least the first
// screen size chunk).
if (rect.height() > height) {
// just enough to get screen size chunk on
scrollYDelta += (rect.top - listUnfadedTop);
} else {
// get entire rect at bottom of screen
scrollYDelta += (rect.bottom - listUnfadedBottom);
}
// make sure we aren't scrolling beyond the end of our children
int distanceToBottom = bottomOfBottomChild - listUnfadedBottom;
scrollYDelta = Math.min(scrollYDelta, distanceToBottom);
} else if (rect.top < listUnfadedTop && rect.bottom < listUnfadedBottom) {
// need to MOVE UP to get it in view: move up just enough so that
// entire rectangle is in view (or at least the first screen
// size chunk of it).
if (rect.height() > height) {
// screen size chunk
scrollYDelta -= (listUnfadedBottom - rect.bottom);
} else {
// entire rect at top
scrollYDelta -= (listUnfadedTop - rect.top);
}
// make sure we aren't scrolling any further than the top our children
int top = getChildAt(0).getTop();
int deltaToTop = top - listUnfadedTop;
scrollYDelta = Math.max(scrollYDelta, deltaToTop);
}
final boolean scroll = scrollYDelta != 0;
if (scroll) {
scrollListItemsBy(-scrollYDelta);
positionSelector(INVALID_POSITION, child);
mSelectedTop = child.getTop();
invalidate();
}
return scroll;
}
/**
* {@inheritDoc}
*/
@Override
void fillGap(boolean down) {
final int count = getChildCount();
if (down) {
int paddingTop = 0;
if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
paddingTop = getListPaddingTop();
}
final int startOffset = count > 0 ? getChildAt(count - 1).getBottom() + mDividerHeight :
paddingTop;
fillDown(mFirstPosition + count, startOffset);
correctTooHigh(getChildCount());
} else {
int paddingBottom = 0;
if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
paddingBottom = getListPaddingBottom();
}
final int startOffset = count > 0 ? getChildAt(0).getTop() - mDividerHeight :
getHeight() - paddingBottom;
fillUp(mFirstPosition - 1, startOffset);
correctTooLow(getChildCount());
}
}
/**
* Fills the list from pos down to the end of the list view.
*
* @param pos The first position to put in the list
*
* @param nextTop The location where the top of the item associated with pos
* should be drawn
*
* @return The view that is currently selected, if it happens to be in the
* range that we draw.
*/
private View fillDown(int pos, int nextTop) {
View selectedView = null;
int end = (mBottom - mTop);
if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
end -= mListPadding.bottom;
}
while (nextTop < end && pos < mItemCount) {
// is this the selected item?
boolean selected = pos == mSelectedPosition;
View child = makeAndAddView(pos, nextTop, true, mListPadding.left, selected);
nextTop = child.getBottom() + mDividerHeight;
if (selected) {
selectedView = child;
}
pos++;
}
return selectedView;
}
/**
* Fills the list from pos up to the top of the list view.
*
* @param pos The first position to put in the list
*
* @param nextBottom The location where the bottom of the item associated
* with pos should be drawn
*
* @return The view that is currently selected
*/
private View fillUp(int pos, int nextBottom) {
View selectedView = null;
int end = 0;
if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
end = mListPadding.top;
}
while (nextBottom > end && pos >= 0) {
// is this the selected item?
boolean selected = pos == mSelectedPosition;
View child = makeAndAddView(pos, nextBottom, false, mListPadding.left, selected);
nextBottom = child.getTop() - mDividerHeight;
if (selected) {
selectedView = child;
}
pos--;
}
mFirstPosition = pos + 1;
return selectedView;
}
/**
* Fills the list from top to bottom, starting with mFirstPosition
*
* @param nextTop The location where the top of the first item should be
* drawn
*
* @return The view that is currently selected
*/
private View fillFromTop(int nextTop) {
mFirstPosition = Math.min(mFirstPosition, mSelectedPosition);
mFirstPosition = Math.min(mFirstPosition, mItemCount - 1);
if (mFirstPosition < 0) {
mFirstPosition = 0;
}
return fillDown(mFirstPosition, nextTop);
}
/**
* Put mSelectedPosition in the middle of the screen and then build up and
* down from there. This method forces mSelectedPosition to the center.
*
* @param childrenTop Top of the area in which children can be drawn, as
* measured in pixels
* @param childrenBottom Bottom of the area in which children can be drawn,
* as measured in pixels
* @return Currently selected view
*/
private View fillFromMiddle(int childrenTop, int childrenBottom) {
int height = childrenBottom - childrenTop;
int position = reconcileSelectedPosition();
View sel = makeAndAddView(position, childrenTop, true,
mListPadding.left, true);
mFirstPosition = position;
int selHeight = sel.getMeasuredHeight();
if (selHeight <= height) {
sel.offsetTopAndBottom((height - selHeight) / 2);
}
fillAboveAndBelow(sel, position);
if (!mStackFromBottom) {
correctTooHigh(getChildCount());
} else {
correctTooLow(getChildCount());
}
return sel;
}
/**
* Once the selected view as been placed, fill up the visible area above and
* below it.
*
* @param sel The selected view
* @param position The position corresponding to sel
*/
private void fillAboveAndBelow(View sel, int position) {
final int dividerHeight = mDividerHeight;
if (!mStackFromBottom) {
fillUp(position - 1, sel.getTop() - dividerHeight);
adjustViewsUpOrDown();
fillDown(position + 1, sel.getBottom() + dividerHeight);
} else {
fillDown(position + 1, sel.getBottom() + dividerHeight);
adjustViewsUpOrDown();
fillUp(position - 1, sel.getTop() - dividerHeight);
}
}
/**
* Fills the grid based on positioning the new selection at a specific
* location. The selection may be moved so that it does not intersect the
* faded edges. The grid is then filled upwards and downwards from there.
*
* @param selectedTop Where the selected item should be
* @param childrenTop Where to start drawing children
* @param childrenBottom Last pixel where children can be drawn
* @return The view that currently has selection
*/
private View fillFromSelection(int selectedTop, int childrenTop, int childrenBottom) {
int fadingEdgeLength = getVerticalFadingEdgeLength();
final int selectedPosition = mSelectedPosition;
View sel;
final int topSelectionPixel = getTopSelectionPixel(childrenTop, fadingEdgeLength,
selectedPosition);
final int bottomSelectionPixel = getBottomSelectionPixel(childrenBottom, fadingEdgeLength,
selectedPosition);
sel = makeAndAddView(selectedPosition, selectedTop, true, mListPadding.left, true);
// Some of the newly selected item extends below the bottom of the list
if (sel.getBottom() > bottomSelectionPixel) {
// Find space available above the selection into which we can scroll
// upwards
final int spaceAbove = sel.getTop() - topSelectionPixel;
// Find space required to bring the bottom of the selected item
// fully into view
final int spaceBelow = sel.getBottom() - bottomSelectionPixel;
final int offset = Math.min(spaceAbove, spaceBelow);
// Now offset the selected item to get it into view
sel.offsetTopAndBottom(-offset);
} else if (sel.getTop() < topSelectionPixel) {
// Find space required to bring the top of the selected item fully
// into view
final int spaceAbove = topSelectionPixel - sel.getTop();
// Find space available below the selection into which we can scroll
// downwards
final int spaceBelow = bottomSelectionPixel - sel.getBottom();
final int offset = Math.min(spaceAbove, spaceBelow);
// Offset the selected item to get it into view
sel.offsetTopAndBottom(offset);
}
// Fill in views above and below
fillAboveAndBelow(sel, selectedPosition);
if (!mStackFromBottom) {
correctTooHigh(getChildCount());
} else {
correctTooLow(getChildCount());
}
return sel;
}
/**
* Calculate the bottom-most pixel we can draw the selection into
*
* @param childrenBottom Bottom pixel were children can be drawn
* @param fadingEdgeLength Length of the fading edge in pixels, if present
* @param selectedPosition The position that will be selected
* @return The bottom-most pixel we can draw the selection into
*/
private int getBottomSelectionPixel(int childrenBottom, int fadingEdgeLength,
int selectedPosition) {
int bottomSelectionPixel = childrenBottom;
if (selectedPosition != mItemCount - 1) {
bottomSelectionPixel -= fadingEdgeLength;
}
return bottomSelectionPixel;
}
/**
* Calculate the top-most pixel we can draw the selection into
*
* @param childrenTop Top pixel were children can be drawn
* @param fadingEdgeLength Length of the fading edge in pixels, if present
* @param selectedPosition The position that will be selected
* @return The top-most pixel we can draw the selection into
*/
private int getTopSelectionPixel(int childrenTop, int fadingEdgeLength, int selectedPosition) {
// first pixel we can draw the selection into
int topSelectionPixel = childrenTop;
if (selectedPosition > 0) {
topSelectionPixel += fadingEdgeLength;
}
return topSelectionPixel;
}
/**
* Smoothly scroll to the specified adapter position. The view will
* scroll such that the indicated position is displayed.
* @param position Scroll to this adapter position.
*/
@android.view.RemotableViewMethod
public void smoothScrollToPosition(int position) {
super.smoothScrollToPosition(position);
}
/**
* Smoothly scroll to the specified adapter position offset. The view will
* scroll such that the indicated position is displayed.
* @param offset The amount to offset from the adapter position to scroll to.
*/
@android.view.RemotableViewMethod
public void smoothScrollByOffset(int offset) {
super.smoothScrollByOffset(offset);
}
/**
* Fills the list based on positioning the new selection relative to the old
* selection. The new selection will be placed at, above, or below the
* location of the new selection depending on how the selection is moving.
* The selection will then be pinned to the visible part of the screen,
* excluding the edges that are faded. The list is then filled upwards and
* downwards from there.
*
* @param oldSel The old selected view. Useful for trying to put the new
* selection in the same place
* @param newSel The view that is to become selected. Useful for trying to
* put the new selection in the same place
* @param delta Which way we are moving
* @param childrenTop Where to start drawing children
* @param childrenBottom Last pixel where children can be drawn
* @return The view that currently has selection
*/
private View moveSelection(View oldSel, View newSel, int delta, int childrenTop,
int childrenBottom) {
int fadingEdgeLength = getVerticalFadingEdgeLength();
final int selectedPosition = mSelectedPosition;
View sel;
final int topSelectionPixel = getTopSelectionPixel(childrenTop, fadingEdgeLength,
selectedPosition);
final int bottomSelectionPixel = getBottomSelectionPixel(childrenTop, fadingEdgeLength,
selectedPosition);
if (delta > 0) {
/*
* Case 1: Scrolling down.
*/
/*
* Before After
* | | | |
* +-------+ +-------+
* | A | | A |
* | 1 | => +-------+
* +-------+ | B |
* | B | | 2 |
* +-------+ +-------+
* | | | |
*
* Try to keep the top of the previously selected item where it was.
* oldSel = A
* sel = B
*/
// Put oldSel (A) where it belongs
oldSel = makeAndAddView(selectedPosition - 1, oldSel.getTop(), true,
mListPadding.left, false);
final int dividerHeight = mDividerHeight;
// Now put the new selection (B) below that
sel = makeAndAddView(selectedPosition, oldSel.getBottom() + dividerHeight, true,
mListPadding.left, true);
// Some of the newly selected item extends below the bottom of the list
if (sel.getBottom() > bottomSelectionPixel) {
// Find space available above the selection into which we can scroll upwards
int spaceAbove = sel.getTop() - topSelectionPixel;
// Find space required to bring the bottom of the selected item fully into view
int spaceBelow = sel.getBottom() - bottomSelectionPixel;
// Don't scroll more than half the height of the list
int halfVerticalSpace = (childrenBottom - childrenTop) / 2;
int offset = Math.min(spaceAbove, spaceBelow);
offset = Math.min(offset, halfVerticalSpace);
// We placed oldSel, so offset that item
oldSel.offsetTopAndBottom(-offset);
// Now offset the selected item to get it into view
sel.offsetTopAndBottom(-offset);
}
// Fill in views above and below
if (!mStackFromBottom) {
fillUp(mSelectedPosition - 2, sel.getTop() - dividerHeight);
adjustViewsUpOrDown();
fillDown(mSelectedPosition + 1, sel.getBottom() + dividerHeight);
} else {
fillDown(mSelectedPosition + 1, sel.getBottom() + dividerHeight);
adjustViewsUpOrDown();
fillUp(mSelectedPosition - 2, sel.getTop() - dividerHeight);
}
} else if (delta < 0) {
/*