android ListView
/* * 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 android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Rect;import android.graphics.PixelFormat;import android.graphics.Paint;import android.graphics.drawable.Drawable;import android.graphics.drawable.ColorDrawable;import android.os.Parcel;import android.os.Parcelable;import android.util.AttributeSet;import android.util.SparseBooleanArray;import android.view.FocusFinder;import android.view.KeyEvent;import android.view.MotionEvent;import android.view.View;import android.view.ViewDebug;import android.view.ViewGroup;import android.view.ViewParent;import android.view.SoundEffectConstants;import android.view.accessibility.AccessibilityEvent;import com.google.android.collect.Lists;import com.android.internal.R;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. * * @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_choiceMode * @attr ref android.R.styleable#ListView_headerDividersEnabled * @attr ref android.R.styleable#ListView_footerDividersEnabled */public class ListView extends AbsListView { /** * Used to indicate a no preference for a position type. */ static final int NO_POSITION = -1; /** * Normal list that does not indicate choices */ public static final int CHOICE_MODE_NONE = 0; /** * The list allows up to one choice */ public static final int CHOICE_MODE_SINGLE = 1; /** * The list allows multiple choices */ public static final int CHOICE_MODE_MULTIPLE = 2; /** * 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; private boolean mIsCacheColorOpaque; private boolean mDividerIsOpaque; private boolean mClipDivider; private boolean mHeaderDividersEnabled; private boolean mFooterDividersEnabled; private boolean mAreAllItemsSelectable = true; private boolean mItemsCanFocus = false; private int mChoiceMode = CHOICE_MODE_NONE; private SparseBooleanArray mCheckStates; // 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 ArrowScrollFocusResult mArrowScrollFocusResult = new ArrowScrollFocusResult(); 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); } // 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); } setChoiceMode(a.getInt(R.styleable.ListView_choiceMode, CHOICE_MODE_NONE)); 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 that will also account for header * 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) { 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); } /** * 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 that will also account for header * 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 (((HeaderViewListAdapter) mAdapter).removeHeader(v)) { 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 that will also account for header * 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) { 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 (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 that will also account for header 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 (((HeaderViewListAdapter) mAdapter).removeFooter(v)) { 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 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 (null != mAdapter) { 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; 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(); } if (mCheckStates != null) { mCheckStates.clear(); } 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(child); mSelectedTop = child.getTop(); invalidate(); } return scroll; } /** * {@inheritDoc} */ @Override void fillGap(boolean down) { final int count = getChildCount(); if (down) { final int startOffset = count > 0 ? getChildAt(count - 1).getBottom() + mDividerHeight : getListPaddingTop(); fillDown(mFirstPosition + count, startOffset); correctTooHigh(getChildCount()); } else { final int startOffset = count > 0 ? getChildAt(0).getTop() - mDividerHeight : getHeight() - getListPaddingBottom(); 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) - 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 = 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; } /** * 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) { /* * Case 2: Scrolling up. */ /* * Before After * | | | | * +-------+ +-------+ * | A | | A | * +-------+ => | 1 | * | B | +-------+ * | 2 | | B | * +-------+ +-------+ * | | | | * * Try to keep the top of the item about to become selected where it was. * newSel = A * olSel = B */ if (newSel != null) { // Try to position the top of newSel (A) where it was before it was selected sel = makeAndAddView(selectedPosition, newSel.getTop(), true, mListPadding.left, true); } else { // If (A) was not on screen and so did not have a view, position // it above the oldSel (B) sel = makeAndAddView(selectedPosition, oldSel.getTop(), false, mListPadding.left, true); } // Some of the newly selected item extends above the top of the list if (sel.getTop() < topSelectionPixel) { // Find space required to bring the top of the selected item fully into view int spaceAbove = topSelectionPixel - sel.getTop(); // Find space available below the selection into which we can scroll downwards int spaceBelow = bottomSelectionPixel - sel.getBottom(); // 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); // Offset the selected item to get it into view sel.offsetTopAndBottom(offset); } // Fill in views above and below fillAboveAndBelow(sel, selectedPosition); } else { int oldTop = oldSel.getTop(); /* * Case 3: Staying still */ sel = makeAndAddView(selectedPosition, oldTop, true, mListPadding.left, true); // We're staying still... if (oldTop < childrenTop) { // ... but the top of the old selection was off screen. // (This can happen if the data changes size out from under us) int newBottom = sel.getBottom(); if (newBottom < childrenTop + 20) { // Not enough visible -- bring it onscreen sel.offsetTopAndBottom(childrenTop - sel.getTop()); } } // Fill in views above and below fillAboveAndBelow(sel, selectedPosition); } return sel; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // Sets up mListPadding super.onMeasure(widthMeasureSpec, heightMeasureSpec); int widthMode = MeasureSpec.getMode(widthMeasureSpec); int heightMode = MeasureSpec.getMode(heightMeasureSpec); int widthSize = MeasureSpec.getSize(widthMeasureSpec); int heightSize = MeasureSpec.getSize(heightMeasureSpec); int childWidth = 0; int childHeight = 0; mItemCount = mAdapter == null ? 0 : mAdapter.getCount(); if (mItemCount > 0 && (widthMode == MeasureSpec.UNSPECIFIED || heightMode == MeasureSpec.UNSPECIFIED)) { final View child = obtainView(0); measureScrapChild(child, 0, widthMeasureSpec); childWidth = child.getMeasuredWidth(); childHeight = child.getMeasuredHeight(); if (recycleOnMeasure()) { mRecycler.addScrapView(child); } } if (widthMode == MeasureSpec.UNSPECIFIED) { widthSize = mListPadding.left + mListPadding.right + childWidth + getVerticalScrollbarWidth(); } if (heightMode == MeasureSpec.UNSPECIFIED) { heightSize = mListPadding.top + mListPadding.bottom + childHeight + getVerticalFadingEdgeLength() * 2; } if (heightMode == MeasureSpec.AT_MOST) { // TODO: after first layout we should maybe start at the first visible position, not 0 heightSize = measureHeightOfChildren(widthMeasureSpec, 0, NO_POSITION, heightSize, -1); } setMeasuredDimension(widthSize, heightSize); mWidthMeasureSpec = widthMeasureSpec; } private void measureScrapChild(View child, int position, int widthMeasureSpec) { LayoutParams p = (LayoutParams) child.getLayoutParams(); if (p == null) { p = new LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT, 0); child.setLayoutParams(p); } p.viewType = mAdapter.getItemViewType(position); int childWidthSpec = ViewGroup.getChildMeasureSpec(widthMeasureSpec, mListPadding.left + mListPadding.right, p.width); int lpHeight = p.height; int childHeightSpec; if (lpHeight > 0) { childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY); } else { childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); } child.measure(childWidthSpec, childHeightSpec); } /** * @return True to recycle the views used to measure this ListView in * UNSPECIFIED/AT_MOST modes, false otherwise. * @hide */ @ViewDebug.ExportedProperty protected boolean recycleOnMeasure() { return true; } /** * Measures the height of the given range of children (inclusive) and * returns the height with this ListView's padding and divider heights * included. If maxHeight is provided, the measuring will stop when the * current height reaches maxHeight. * * @param widthMeasureSpec The width measure spec to be given to a child's * {@link View#measure(int, int)}. * @param startPosition The position of the first child to be shown. * @param endPosition The (inclusive) position of the last child to be * shown. Specify {@link #NO_POSITION} if the last child should be * the last available child from the adapter. * @param maxHeight The maximum height that will be returned (if all the * children don't fit in this value, this value will be * returned). * @param disallowPartialChildPosition In general, whether the returned * height should only contain entire children. This is more * powerful--it is the first inclusive position at which partial * children will not be allowed. Example: it looks nice to have * at least 3 completely visible children, and in portrait this * will most likely fit; but in landscape there could be times * when even 2 children can not be completely shown, so a value * of 2 (remember, inclusive) would be good (assuming * startPosition is 0). * @return The height of this ListView with the given children. */ final int measureHeightOfChildren(int widthMeasureSpec, int startPosition, int endPosition, final int maxHeight, int disallowPartialChildPosition) { final ListAdapter adapter = mAdapter; if (adapter == null) { return mListPadding.top + mListPadding.bottom; } // Include the padding of the list int returnedHeight = mListPadding.top + mListPadding.bottom; final int dividerHeight = ((mDividerHeight > 0) && mDivider != null) ? mDividerHeight : 0; // The previous height value that was less than maxHeight and contained // no partial children int prevHeightWithoutPartialChild = 0; int i; View child; // mItemCount - 1 since endPosition parameter is inclusive endPosition = (endPosition == NO_POSITION) ? adapter.getCount() - 1 : endPosition; final AbsListView.RecycleBin recycleBin = mRecycler; final boolean recyle = recycleOnMeasure(); for (i = startPosition; i <= endPosition; ++i) { child = obtainView(i); measureScrapChild(child, i, widthMeasureSpec); if (i > 0) { // Count the divider for all but one child returnedHeight += dividerHeight; } // Recycle the view before we possibly return from the method if (recyle) { recycleBin.addScrapView(child); } returnedHeight += child.getMeasuredHeight(); if (returnedHeight >= maxHeight) { // We went over, figure out which height to return.If returnedHeight > maxHeight, // then the i'th position did not fit completely. return (disallowPartialChildPosition >= 0) // Disallowing is enabled (> -1) && (i > disallowPartialChildPosition) // We've past the min pos && (prevHeightWithoutPartialChild > 0) // We have a prev height && (returnedHeight != maxHeight) // i'th child did not fit completely ? prevHeightWithoutPartialChild : maxHeight; } if ((disallowPartialChildPosition >= 0) && (i >= disallowPartialChildPosition)) { prevHeightWithoutPartialChild = returnedHeight; } } // At this point, we went through the range of children, and they each // completely fit, so return the returnedHeight return returnedHeight; } @Override int findMotionRow(int y) { int childCount = getChildCount(); if (childCount > 0) { for (int i = 0; i < childCount; i++) { View v = getChildAt(i); if (y <= v.getBottom()) { return mFirstPosition + i; } } return mFirstPosition + childCount - 1; } return INVALID_POSITION; } /** * Put a specific item at a specific location on the screen and then build * up and down from there. * * @param position The reference view to use as the starting point * @param top Pixel offset from the top of this view to the top of the * reference view. * * @return The selected view, or null if the selected view is outside the * visible area. */ private View fillSpecific(int position, int top) { boolean tempIsSelected = position == mSelectedPosition; View temp = makeAndAddView(position, top, true, mListPadding.left, tempIsSelected); // Possibly changed again in fillUp if we add rows above this one. mFirstPosition = position; View above; View below; final int dividerHeight = mDividerHeight; if (!mStackFromBottom) { above = fillUp(position - 1, temp.getTop() - dividerHeight); // This will correct for the top of the first view not touching the top of the list adjustViewsUpOrDown(); below = fillDown(position + 1, temp.getBottom() + dividerHeight); int childCount = getChildCount(); if (childCount > 0) { correctTooHigh(childCount); } } else { below = fillDown(position + 1, temp.getBottom() + dividerHeight); // This will correct for the bottom of the last view not touching the bottom of the list adjustViewsUpOrDown(); above = fillUp(position - 1, temp.getTop() - dividerHeight); int childCount = getChildCount(); if (childCount > 0) { correctTooLow(childCount); } } if (tempIsSelected) { return temp; } else if (above != null) { return above; } else { return below; } } /** * Check if we have dragged the bottom of the list too high (we have pushed the * top element off the top of the screen when we did not need to). Correct by sliding * everything back down. * * @param childCount Number of children */ private void correctTooHigh(int childCount) { // First see if the last item is visible. If it is not, it is OK for the // top of the list to be pushed up. int lastPosition = mFirstPosition + childCount - 1; if (lastPosition == mItemCount - 1 && childCount > 0) { // Get the last child ... final View lastChild = getChildAt(childCount - 1); // ... and its bottom edge final int lastBottom = lastChild.getBottom(); // This is bottom of our drawable area final int end = (mBottom - mTop) - mListPadding.bottom; // This is how far the bottom edge of the last view is from the bottom of the // drawable area int bottomOffset = end - lastBottom; View firstChild = getChildAt(0); final int firstTop = firstChild.getTop(); // Make sure we are 1) Too high, and 2) Either there are more rows above the // first row or the first row is scrolled off the top of the drawable area if (bottomOffset > 0 && (mFirstPosition > 0 || firstTop < mListPadding.top)){ if (mFirstPosition == 0) { // Don't pull the top too far down bottomOffset = Math.min(bottomOffset, mListPadding.top - firstTop); } // Move everything down offsetChildrenTopAndBottom(bottomOffset); if (mFirstPosition > 0) { // Fill the gap that was opened above mFirstPosition with more rows, if // possible fillUp(mFirstPosition - 1, firstChild.getTop() - mDividerHeight); // Close up the remaining gap adjustViewsUpOrDown(); } } } } /** * Check if we have dragged the bottom of the list too low (we have pushed the * bottom element off the bottom of the screen when we did not need to). Correct by sliding * everything back up. * * @param childCount Number of children */ private void correctTooLow(int childCount) { // First see if the first item is visible. If it is not, it is OK for the // bottom of the list to be pushed down. if (mFirstPosition == 0 && childCount > 0) { // Get the first child ... final View firstChild = getChildAt(0); // ... and its top edge final int firstTop = firstChild.getTop(); // This is top of our drawable area final int start = mListPadding.top; // This is bottom of our drawable area final int end = (mBottom - mTop) - mListPadding.bottom; // This is how far the top edge of the first view is from the top of the // drawable area int topOffset = firstTop - start; View lastChild = getChildAt(childCount - 1); final int lastBottom = lastChild.getBottom(); int lastPosition = mFirstPosition + childCount - 1; // Make sure we are 1) Too low, and 2) Either there are more rows below the // last row or the last row is scrolled off the bottom of the drawable area if (topOffset > 0) { if (lastPosition < mItemCount - 1 || lastBottom > end){ if (lastPosition == mItemCount - 1) { // Don't pull the bottom too far up topOffset = Math.min(topOffset, lastBottom - end); } // Move everything up offsetChildrenTopAndBottom(-topOffset); if (lastPosition < mItemCount - 1) { // Fill the gap that was opened below the last position with more rows, if // possible fillDown(lastPosition + 1, lastChild.getBottom() + mDividerHeight); // Close up the remaining gap adjustViewsUpOrDown(); } } else if (lastPosition == mItemCount - 1) { adjustViewsUpOrDown(); } } } } @Override protected void layoutChildren() { final boolean blockLayoutRequests = mBlockLayoutRequests; if (!blockLayoutRequests) { mBlockLayoutRequests = true; } else { return; } try { super.layoutChildren(); invalidate(); if (mAdapter == null) { resetList(); invokeOnItemScrollListener(); return; } int childrenTop = mListPadding.top; int childrenBottom = mBottom - mTop - mListPadding.bottom; int childCount = getChildCount(); int index; int delta = 0; View sel; View oldSel = null; View oldFirst = null; View newSel = null; View focusLayoutRestoreView = null; // Remember stuff we will need down below switch (mLayoutMode) { case LAYOUT_SET_SELECTION: index = mNextSelectedPosition - mFirstPosition; if (index >= 0 && index < childCount) { newSel = getChildAt(index); } break; case LAYOUT_FORCE_TOP: case LAYOUT_FORCE_BOTTOM: case LAYOUT_SPECIFIC: case LAYOUT_SYNC: break; case LAYOUT_MOVE_SELECTION: default: // Remember the previously selected view index = mSelectedPosition - mFirstPosition; if (index >= 0 && index < childCount) { oldSel = getChildAt(index); } // Remember the previous first child oldFirst = getChildAt(0); if (mNextSelectedPosition >= 0) { delta = mNextSelectedPosition - mSelectedPosition; } // Caution: newSel might be null newSel = getChildAt(index + delta); } boolean dataChanged = mDataChanged; if (dataChanged) { handleDataChanged(); } // Handle the empty set by removing all views that are visible // and calling it a day if (mItemCount == 0) { resetList(); invokeOnItemScrollListener(); return; } else if (mItemCount != mAdapter.getCount()) { throw new IllegalStateException("The content of the adapter has changed but " + "ListView did not receive a notification. Make sure the content of " + "your adapter is not modified from a background thread, but only " + "from the UI thread. "); } setSelectedPositionInt(mNextSelectedPosition); // Pull all children into the RecycleBin. // These views will be reused if possible final int firstPosition = mFirstPosition; final RecycleBin recycleBin = mRecycler; // reset the focus restoration View focusLayoutRestoreDirectChild = null; // Don't put header or footer views into the Recycler. Those are // already cached in mHeaderViews; if (dataChanged) { for (int i = 0; i < childCount; i++) { recycleBin.addScrapView(getChildAt(i)); if (ViewDebug.TRACE_RECYCLER) { ViewDebug.trace(getChildAt(i), ViewDebug.RecyclerTraceType.MOVE_TO_SCRAP_HEAP, index, i); } } } else { recycleBin.fillActiveViews(childCount, firstPosition); } // take focus back to us temporarily to avoid the eventual // call to clear focus when removing the focused child below // from messing things up when ViewRoot assigns focus back // to someone else final View focusedChild = getFocusedChild(); if (focusedChild != null) { // TODO: in some cases focusedChild.getParent() == null // we can remember the focused view to restore after relayout if the // data hasn't changed, or if the focused position is a header or footer if (!dataChanged || isDirectChildHeaderOrFooter(focusedChild)) { focusLayoutRestoreDirectChild = focusedChild; // remember the specific view that had focus focusLayoutRestoreView = findFocus(); if (focusLayoutRestoreView != null) { // tell it we are going to mess with it focusLayoutRestoreView.onStartTemporaryDetach(); } } requestFocus(); } // Clear out old views //removeAllViewsInLayout(); detachAllViewsFromParent(); switch (mLayoutMode) { case LAYOUT_SET_SELECTION: if (newSel != null) { sel = fillFromSelection(newSel.getTop(), childrenTop, childrenBottom); } else { sel = fillFromMiddle(childrenTop, childrenBottom); } break; case LAYOUT_SYNC: sel = fillSpecific(mSyncPosition, mSpecificTop); break; case LAYOUT_FORCE_BOTTOM: sel = fillUp(mItemCount - 1, childrenBottom); adjustViewsUpOrDown(); break; case LAYOUT_FORCE_TOP: mFirstPosition = 0; sel = fillFromTop(childrenTop); adjustViewsUpOrDown(); break; case LAYOUT_SPECIFIC: sel = fillSpecific(reconcileSelectedPosition(), mSpecificTop); break; case LAYOUT_MOVE_SELECTION: sel = moveSelection(oldSel, newSel, delta, childrenTop, childrenBottom); break; default: if (childCount == 0) { if (!mStackFromBottom) { final int position = lookForSelectablePosition(0, true); setSelectedPositionInt(position); sel = fillFromTop(childrenTop); } else { final int position = lookForSelectablePosition(mItemCount - 1, false); setSelectedPositionInt(position); sel = fillUp(mItemCount - 1, childrenBottom); } } else { if (mSelectedPosition >= 0 && mSelectedPosition < mItemCount) { sel = fillSpecific(mSelectedPosition, oldSel == null ? childrenTop : oldSel.getTop()); } else if (mFirstPosition < mItemCount) { sel = fillSpecific(mFirstPosition, oldFirst == null ? childrenTop : oldFirst.getTop()); } else { sel = fillSpecific(0, childrenTop); } } break; } // Flush any cached views that did not get reused above recycleBin.scrapActiveViews(); if (sel != null) { // the current selected item should get focus if items // are focusable if (mItemsCanFocus && hasFocus() && !sel.hasFocus()) { final boolean focusWasTaken = (sel == focusLayoutRestoreDirectChild && focusLayoutRestoreView.requestFocus()) || sel.requestFocus(); if (!focusWasTaken) { // selected item didn't take focus, fine, but still want // to make sure something else outside of the selected view // has focus final View focused = getFocusedChild(); if (focused != null) { focused.clearFocus(); } positionSelector(sel); } else { sel.setSelected(false); mSelectorRect.setEmpty(); } } else { positionSelector(sel); } mSelectedTop = sel.getTop(); } else { if (mTouchMode > TOUCH_MODE_DOWN && mTouchMode < TOUCH_MODE_SCROLL) { View child = getChildAt(mMotionPosition - mFirstPosition); if (child != null) positionSelector(child); } else { mSelectedTop = 0; mSelectorRect.setEmpty(); } // even if there is not selected position, we may need to restore // focus (i.e. something focusable in touch mode) if (hasFocus() && focusLayoutRestoreView != null) { focusLayoutRestoreView.requestFocus(); } } // tell focus view we are done mucking with it, if it is still in // our view hierarchy. if (focusLayoutRestoreView != null && focusLayoutRestoreView.getWindowToken() != null) { focusLayoutRestoreView.onFinishTemporaryDetach(); } mLayoutMode = LAYOUT_NORMAL; mDataChanged = false; mNeedSync = false; setNextSelectedPositionInt(mSelectedPosition); updateScrollIndicators(); if (mItemCount > 0) { checkSelectionChanged(); } invokeOnItemScrollListener(); } finally { if (!blockLayoutRequests) { mBlockLayoutRequests = false; } } } /** * @param child a direct child of this list. * @return Whether child is a header or footer view. */ private boolean isDirectChildHeaderOrFooter(View child) { final ArrayList<FixedViewInfo> headers = mHeaderViewInfos; final int numHeaders = headers.size(); for (int i = 0; i < numHeaders; i++) { if (child == headers.get(i).view) { return true; } } final ArrayList<FixedViewInfo> footers = mFooterViewInfos; final int numFooters = footers.size(); for (int i = 0; i < numFooters; i++) { if (child == footers.get(i).view) { return true; } } return false; } /** * Obtain the view and add it to our list of children. The view can be made * fresh, converted from an unused view, or used as is if it was in the * recycle bin. * * @param position Logical position in the list * @param y Top or bottom edge of the view to add * @param flow If flow is true, align top edge to y. If false, align bottom * edge to y. * @param childrenLeft Left edge where children should be positioned * @param selected Is this position selected? * @return View that was added */ private View makeAndAddView(int position, int y, boolean flow, int childrenLeft, boolean selected) { View child; if (!mDataChanged) { // Try to use an exsiting view for this position child = mRecycler.getActiveView(position); if (child != null) { if (ViewDebug.TRACE_RECYCLER) { ViewDebug.trace(child, ViewDebug.RecyclerTraceType.RECYCLE_FROM_ACTIVE_HEAP, position, getChildCount()); } // Found it -- we're using an existing child // This just needs to be positioned setupChild(child, position, y, flow, childrenLeft, selected, true); return child; } } // Make a new view for this position, or convert an unused view if possible child = obtainView(position); // This needs to be positioned and measured setupChild(child, position, y, flow, childrenLeft, selected, false); return child; } /** * Add a view as a child and make sure it is measured (if necessary) and * positioned properly. * * @param child The view to add * @param position The position of this child * @param y The y po
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