关于ViewPager的懒加载问题

默认情况下，系统自带的viewpager至少会提前加载下一个页面，无法禁止，想要禁止，只能通过自定义viewpager来实现；

这是在Android open source 上找到的懒加载viewpager

如果不好拷贝的话直接到https://github.com/jiang111/LazyViewPager  上下载。。

/* * Copyright (C) 2011 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. */import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import android.content.Context;import android.database.DataSetObserver;import android.graphics.Canvas;import android.graphics.Rect;import android.graphics.drawable.Drawable;import android.os.Parcel;import android.os.Parcelable;import android.os.SystemClock;import android.support.v4.os.ParcelableCompat;import android.support.v4.os.ParcelableCompatCreatorCallbacks;import android.support.v4.view.KeyEventCompat;import android.support.v4.view.MotionEventCompat;import android.support.v4.view.PagerAdapter;import android.support.v4.view.VelocityTrackerCompat;import android.support.v4.view.ViewCompat;import android.support.v4.view.ViewConfigurationCompat;import android.support.v4.widget.EdgeEffectCompat;import android.util.AttributeSet;import android.util.Log;import android.view.FocusFinder;import android.view.KeyEvent;import android.view.MotionEvent;import android.view.SoundEffectConstants;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.ViewParent;import android.view.accessibility.AccessibilityEvent;import android.view.animation.Interpolator;import android.widget.Scroller;/** * Layout manager that allows the user to flip left and right through pages of * data. You supply an implementation of a * {@link android.support.v4.view.PagerAdapter} to generate the pages that the * view shows. *  * <p> * Note this class is currently under early design and development. The API will * likely change in later updates of the compatibility library, requiring * changes to the source code of apps when they are compiled against the newer * version. * </p> */public class LazyViewPager extends ViewGroup {private static final String TAG = "LazyViewPager";private static final boolean DEBUG = false;private static final boolean USE_CACHE = false;private static final int DEFAULT_OFFSCREEN_PAGES = 0;// 默认的加载页面,ViewPager是1个,所以会加载两个Fragmentprivate static final int MAX_SETTLE_DURATION = 600; // msstatic class ItemInfo {Object object;int position;boolean scrolling;}private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>() {@Overridepublic int compare(ItemInfo lhs, ItemInfo rhs) {return lhs.position - rhs.position;}};private static final Interpolator sInterpolator = new Interpolator() {public float getInterpolation(float t) {// _o(t) = t * t * ((tension + 1) * t + tension)// o(t) = _o(t - 1) + 1t -= 1.0f;return t * t * t + 1.0f;}};private final ArrayList<ItemInfo> mItems = new ArrayList<ItemInfo>();private PagerAdapter mAdapter;private int mCurItem; // Index of currently displayed page.private int mRestoredCurItem = -1;private Parcelable mRestoredAdapterState = null;private ClassLoader mRestoredClassLoader = null;private Scroller mScroller;private PagerObserver mObserver;private int mPageMargin;private Drawable mMarginDrawable;private int mChildWidthMeasureSpec;private int mChildHeightMeasureSpec;private boolean mInLayout;private boolean mScrollingCacheEnabled;private boolean mPopulatePending;private boolean mScrolling;private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;private boolean mIsBeingDragged;private boolean mIsUnableToDrag;private int mTouchSlop;private float mInitialMotionX;/** * Position of the last motion event. */private float mLastMotionX;private float mLastMotionY;/** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */private int mActivePointerId = INVALID_POINTER;/** * Sentinel value for no current active pointer. Used by * {@link #mActivePointerId}. */private static final int INVALID_POINTER = -1;/** * Determines speed during touch scrolling */private VelocityTracker mVelocityTracker;private int mMinimumVelocity;private int mMaximumVelocity;private float mBaseLineFlingVelocity;private float mFlingVelocityInfluence;private boolean mFakeDragging;private long mFakeDragBeginTime;private EdgeEffectCompat mLeftEdge;private EdgeEffectCompat mRightEdge;private boolean mFirstLayout = true;private OnPageChangeListener mOnPageChangeListener;/** * Indicates that the pager is in an idle, settled state. The current page * is fully in view and no animation is in progress. */public static final int SCROLL_STATE_IDLE = 0;/** * Indicates that the pager is currently being dragged by the user. */public static final int SCROLL_STATE_DRAGGING = 1;/** * Indicates that the pager is in the process of settling to a final * position. */public static final int SCROLL_STATE_SETTLING = 2;private int mScrollState = SCROLL_STATE_IDLE;/** * Callback interface for responding to changing state of the selected page. */public interface OnPageChangeListener {/** * This method will be invoked when the current page is scrolled, either * as part of a programmatically initiated smooth scroll or a user * initiated touch scroll. *  * @param position *            Position index of the first page currently being *            displayed. Page position+1 will be visible if *            positionOffset is nonzero. * @param positionOffset *            Value from [0, 1) indicating the offset from the page at *            position. * @param positionOffsetPixels *            Value in pixels indicating the offset from position. */public void onPageScrolled(int position, float positionOffset,int positionOffsetPixels);/** * This method will be invoked when a new page becomes selected. * Animation is not necessarily complete. *  * @param position *            Position index of the new selected page. */public void onPageSelected(int position);/** * Called when the scroll state changes. Useful for discovering when the * user begins dragging, when the pager is automatically settling to the * current page, or when it is fully stopped/idle. *  * @param state *            The new scroll state. * @see android.support.v4.view.ViewPager#SCROLL_STATE_IDLE * @see android.support.v4.view.ViewPager#SCROLL_STATE_DRAGGING * @see android.support.v4.view.ViewPager#SCROLL_STATE_SETTLING */public void onPageScrollStateChanged(int state);}/** * Simple implementation of the * {@link com.bxg.news.view.LazyViewPager.OnPageChangeListener} * interface with stub implementations of each method. Extend this if you do * not intend to override every method of * {@link com.bxg.news.view.LazyViewPager.OnPageChangeListener}. */public static class SimpleOnPageChangeListener implementsOnPageChangeListener {@Overridepublic void onPageScrolled(int position, float positionOffset,int positionOffsetPixels) {// This space for rent}@Overridepublic void onPageSelected(int position) {// This space for rent}@Overridepublic void onPageScrollStateChanged(int state) {// This space for rent}}public LazyViewPager(Context context) {super(context);initViewPager();}public LazyViewPager(Context context, AttributeSet attrs) {super(context, attrs);initViewPager();}void initViewPager() {setWillNotDraw(false);setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);setFocusable(true);final Context context = getContext();mScroller = new Scroller(context, sInterpolator);final ViewConfiguration configuration = ViewConfiguration.get(context);mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();mLeftEdge = new EdgeEffectCompat(context);mRightEdge = new EdgeEffectCompat(context);float density = context.getResources().getDisplayMetrics().density;mBaseLineFlingVelocity = 2500.0f * density;mFlingVelocityInfluence = 0.4f;}private void setScrollState(int newState) {if (mScrollState == newState) {return;}mScrollState = newState;if (mOnPageChangeListener != null) {mOnPageChangeListener.onPageScrollStateChanged(newState);}}public void setAdapter(PagerAdapter adapter) {if (mAdapter != null) {mAdapter.unregisterDataSetObserver(mObserver);mAdapter.startUpdate(this);for (int i = 0; i < mItems.size(); i++) {final ItemInfo ii = mItems.get(i);mAdapter.destroyItem(this, ii.position, ii.object);}mAdapter.finishUpdate(this);mItems.clear();removeAllViews();mCurItem = 0;scrollTo(0, 0);}mAdapter = adapter;if (mAdapter != null) {if (mObserver == null) {mObserver = new PagerObserver();}mAdapter.registerDataSetObserver(mObserver);mPopulatePending = false;if (mRestoredCurItem >= 0) {mAdapter.restoreState(mRestoredAdapterState,mRestoredClassLoader);setCurrentItemInternal(mRestoredCurItem, false, true);mRestoredCurItem = -1;mRestoredAdapterState = null;mRestoredClassLoader = null;} else {populate();}}}public PagerAdapter getAdapter() {return mAdapter;}/** * Set the currently selected page. If the ViewPager has already been * through its first layout there will be a smooth animated transition * between the current item and the specified item. *  * @param item *            Item index to select */public void setCurrentItem(int item) {mPopulatePending = false;setCurrentItemInternal(item, !mFirstLayout, false);}/** * Set the currently selected page. *  * @param item *            Item index to select * @param smoothScroll *            True to smoothly scroll to the new item, false to transition *            immediately */public void setCurrentItem(int item, boolean smoothScroll) {mPopulatePending = false;setCurrentItemInternal(item, smoothScroll, false);}public int getCurrentItem() {return mCurItem;}void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {setCurrentItemInternal(item, smoothScroll, always, 0);}void setCurrentItemInternal(int item, boolean smoothScroll, boolean always,int velocity) {if (mAdapter == null || mAdapter.getCount() <= 0) {setScrollingCacheEnabled(false);return;}if (!always && mCurItem == item && mItems.size() != 0) {setScrollingCacheEnabled(false);return;}if (item < 0) {item = 0;} else if (item >= mAdapter.getCount()) {item = mAdapter.getCount() - 1;}final int pageLimit = mOffscreenPageLimit;if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {// We are doing a jump by more than one page. To avoid// glitches, we want to keep all current pages in the view// until the scroll ends.for (int i = 0; i < mItems.size(); i++) {mItems.get(i).scrolling = true;}}final boolean dispatchSelected = mCurItem != item;mCurItem = item;populate();final int destX = (getWidth() + mPageMargin) * item;if (smoothScroll) {smoothScrollTo(destX, 0, velocity);if (dispatchSelected && mOnPageChangeListener != null) {mOnPageChangeListener.onPageSelected(item);}} else {if (dispatchSelected && mOnPageChangeListener != null) {mOnPageChangeListener.onPageSelected(item);}completeScroll();scrollTo(destX, 0);}}public void setOnPageChangeListener(OnPageChangeListener listener) {mOnPageChangeListener = listener;}/** * Returns the number of pages that will be retained to either side of the * current page in the view hierarchy in an idle state. Defaults to 1. *  * @return How many pages will be kept offscreen on either side * @see #setOffscreenPageLimit(int) */public int getOffscreenPageLimit() {return mOffscreenPageLimit;}/** * Set the number of pages that should be retained to either side of the * current page in the view hierarchy in an idle state. Pages beyond this * limit will be recreated from the adapter when needed. *  * <p> * This is offered as an optimization. If you know in advance the number of * pages you will need to support or have lazy-loading mechanisms in place * on your pages, tweaking this setting can have benefits in perceived * smoothness of paging animations and interaction. If you have a small * number of pages (3-4) that you can keep active all at once, less time * will be spent in layout for newly created view subtrees as the user pages * back and forth. * </p> *  * <p> * You should keep this limit low, especially if your pages have complex * layouts. This setting defaults to 1. * </p> *  * @param limit *            How many pages will be kept offscreen in an idle state. */public void setOffscreenPageLimit(int limit) {if (limit < DEFAULT_OFFSCREEN_PAGES) {Log.w(TAG, "Requested offscreen page limit " + limit+ " too small; defaulting to " + DEFAULT_OFFSCREEN_PAGES);limit = DEFAULT_OFFSCREEN_PAGES;}if (limit != mOffscreenPageLimit) {mOffscreenPageLimit = limit;populate();}}/** * Set the margin between pages. *  * @param marginPixels *            Distance between adjacent pages in pixels * @see #getPageMargin() * @see #setPageMarginDrawable(android.graphics.drawable.Drawable) * @see #setPageMarginDrawable(int) */public void setPageMargin(int marginPixels) {final int oldMargin = mPageMargin;mPageMargin = marginPixels;final int width = getWidth();recomputeScrollPosition(width, width, marginPixels, oldMargin);requestLayout();}/** * Return the margin between pages. *  * @return The size of the margin in pixels */public int getPageMargin() {return mPageMargin;}/** * Set a drawable that will be used to fill the margin between pages. *  * @param d *            Drawable to display between pages */public void setPageMarginDrawable(Drawable d) {mMarginDrawable = d;if (d != null)refreshDrawableState();setWillNotDraw(d == null);invalidate();}/** * Set a drawable that will be used to fill the margin between pages. *  * @param resId *            Resource ID of a drawable to display between pages */public void setPageMarginDrawable(int resId) {setPageMarginDrawable(getContext().getResources().getDrawable(resId));}@Overrideprotected boolean verifyDrawable(Drawable who) {return super.verifyDrawable(who) || who == mMarginDrawable;}@Overrideprotected void drawableStateChanged() {super.drawableStateChanged();final Drawable d = mMarginDrawable;if (d != null && d.isStateful()) {d.setState(getDrawableState());}}// We want the duration of the page snap animation to be influenced by the// distance that// the screen has to travel, however, we don't want this duration to be// effected in a// purely linear fashion. Instead, we use this method to moderate the effect// that the distance// of travel has on the overall snap duration.float distanceInfluenceForSnapDuration(float f) {f -= 0.5f; // center the values about 0.f *= 0.3f * Math.PI / 2.0f;return (float) Math.sin(f);}/** * Like {@link android.view.View#scrollBy}, but scroll smoothly instead of * immediately. *  * @param x *            the number of pixels to scroll by on the X axis * @param y *            the number of pixels to scroll by on the Y axis */void smoothScrollTo(int x, int y) {smoothScrollTo(x, y, 0);}/** * Like {@link android.view.View#scrollBy}, but scroll smoothly instead of * immediately. *  * @param x *            the number of pixels to scroll by on the X axis * @param y *            the number of pixels to scroll by on the Y axis * @param velocity *            the velocity associated with a fling, if applicable. (0 *            otherwise) */void smoothScrollTo(int x, int y, int velocity) {if (getChildCount() == 0) {// Nothing to do.setScrollingCacheEnabled(false);return;}int sx = getScrollX();int sy = getScrollY();int dx = x - sx;int dy = y - sy;if (dx == 0 && dy == 0) {completeScroll();setScrollState(SCROLL_STATE_IDLE);return;}setScrollingCacheEnabled(true);mScrolling = true;setScrollState(SCROLL_STATE_SETTLING);final float pageDelta = (float) Math.abs(dx)/ (getWidth() + mPageMargin);int duration = (int) (pageDelta * 100);velocity = Math.abs(velocity);if (velocity > 0) {duration += (duration / (velocity / mBaseLineFlingVelocity))* mFlingVelocityInfluence;} else {duration += 100;}duration = Math.min(duration, MAX_SETTLE_DURATION);mScroller.startScroll(sx, sy, dx, dy, duration);invalidate();}void addNewItem(int position, int index) {ItemInfo ii = new ItemInfo();ii.position = position;ii.object = mAdapter.instantiateItem(this, position);if (index < 0) {mItems.add(ii);} else {mItems.add(index, ii);}}void dataSetChanged() {// This method only gets called if our observer is attached, so mAdapter// is non-null.boolean needPopulate = mItems.size() < 3&& mItems.size() < mAdapter.getCount();int newCurrItem = -1;for (int i = 0; i < mItems.size(); i++) {final ItemInfo ii = mItems.get(i);final int newPos = mAdapter.getItemPosition(ii.object);if (newPos == PagerAdapter.POSITION_UNCHANGED) {continue;}if (newPos == PagerAdapter.POSITION_NONE) {mItems.remove(i);i--;mAdapter.destroyItem(this, ii.position, ii.object);needPopulate = true;if (mCurItem == ii.position) {// Keep the current item in the valid rangenewCurrItem = Math.max(0,Math.min(mCurItem, mAdapter.getCount() - 1));}continue;}if (ii.position != newPos) {if (ii.position == mCurItem) {// Our current item changed position. Follow it.newCurrItem = newPos;}ii.position = newPos;needPopulate = true;}}Collections.sort(mItems, COMPARATOR);if (newCurrItem >= 0) {// TODO This currently causes a jump.setCurrentItemInternal(newCurrItem, false, true);needPopulate = true;}if (needPopulate) {populate();requestLayout();}}void populate() {if (mAdapter == null) {return;}// Bail now if we are waiting to populate. This is to hold off// on creating views from the time the user releases their finger to// fling to a new position until we have finished the scroll to// that position, avoiding glitches from happening at that point.if (mPopulatePending) {if (DEBUG)Log.i(TAG, "populate is pending, skipping for now...");return;}// Also, don't populate until we are attached to a window. This is to// avoid trying to populate before we have restored our view hierarchy// state and conflicting with what is restored.if (getWindowToken() == null) {return;}mAdapter.startUpdate(this);final int pageLimit = mOffscreenPageLimit;final int startPos = Math.max(0, mCurItem - pageLimit);final int N = mAdapter.getCount();final int endPos = Math.min(N - 1, mCurItem + pageLimit);if (DEBUG)Log.v(TAG, "populating: startPos=" + startPos + " endPos=" + endPos);// Add and remove pages in the existing list.int lastPos = -1;for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if ((ii.position < startPos || ii.position > endPos)&& !ii.scrolling) {if (DEBUG)Log.i(TAG, "removing: " + ii.position + " @ " + i);mItems.remove(i);i--;mAdapter.destroyItem(this, ii.position, ii.object);} else if (lastPos < endPos && ii.position > startPos) {// The next item is outside of our range, but we have a gap// between it and the last item where we want to have a page// shown. Fill in the gap.lastPos++;if (lastPos < startPos) {lastPos = startPos;}while (lastPos <= endPos && lastPos < ii.position) {if (DEBUG)Log.i(TAG, "inserting: " + lastPos + " @ " + i);addNewItem(lastPos, i);lastPos++;i++;}}lastPos = ii.position;}// Add any new pages we need at the end.lastPos = mItems.size() > 0 ? mItems.get(mItems.size() - 1).position: -1;if (lastPos < endPos) {lastPos++;lastPos = lastPos > startPos ? lastPos : startPos;while (lastPos <= endPos) {if (DEBUG)Log.i(TAG, "appending: " + lastPos);addNewItem(lastPos, -1);lastPos++;}}if (DEBUG) {Log.i(TAG, "Current page list:");for (int i = 0; i < mItems.size(); i++) {Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);}}ItemInfo curItem = null;for (int i = 0; i < mItems.size(); i++) {if (mItems.get(i).position == mCurItem) {curItem = mItems.get(i);break;}}mAdapter.setPrimaryItem(this, mCurItem,curItem != null ? curItem.object : null);mAdapter.finishUpdate(this);if (hasFocus()) {View currentFocused = findFocus();ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused): null;if (ii == null || ii.position != mCurItem) {for (int i = 0; i < getChildCount(); i++) {View child = getChildAt(i);ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {if (child.requestFocus(FOCUS_FORWARD)) {break;}}}}}}public static class SavedState extends BaseSavedState {int position;Parcelable adapterState;ClassLoader loader;public SavedState(Parcelable superState) {super(superState);}@Overridepublic void writeToParcel(Parcel out, int flags) {super.writeToParcel(out, flags);out.writeInt(position);out.writeParcelable(adapterState, flags);}@Overridepublic String toString() {return "FragmentPager.SavedState{"+ Integer.toHexString(System.identityHashCode(this))+ " position=" + position + "}";}public static final Creator<SavedState> CREATOR = ParcelableCompat.newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() {@Overridepublic SavedState createFromParcel(Parcel in,ClassLoader loader) {return new SavedState(in, loader);}@Overridepublic SavedState[] newArray(int size) {return new SavedState[size];}});SavedState(Parcel in, ClassLoader loader) {super(in);if (loader == null) {loader = getClass().getClassLoader();}position = in.readInt();adapterState = in.readParcelable(loader);this.loader = loader;}}@Overridepublic Parcelable onSaveInstanceState() {Parcelable superState = super.onSaveInstanceState();SavedState ss = new SavedState(superState);ss.position = mCurItem;if (mAdapter != null) {ss.adapterState = mAdapter.saveState();}return ss;}@Overridepublic void onRestoreInstanceState(Parcelable state) {if (!(state instanceof SavedState)) {super.onRestoreInstanceState(state);return;}SavedState ss = (SavedState) state;super.onRestoreInstanceState(ss.getSuperState());if (mAdapter != null) {mAdapter.restoreState(ss.adapterState, ss.loader);setCurrentItemInternal(ss.position, false, true);} else {mRestoredCurItem = ss.position;mRestoredAdapterState = ss.adapterState;mRestoredClassLoader = ss.loader;}}@Overridepublic void addView(View child, int index, LayoutParams params) {if (mInLayout) {addViewInLayout(child, index, params);child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec);} else {super.addView(child, index, params);}if (USE_CACHE) {if (child.getVisibility() != GONE) {child.setDrawingCacheEnabled(mScrollingCacheEnabled);} else {child.setDrawingCacheEnabled(false);}}}ItemInfo infoForChild(View child) {for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if (mAdapter.isViewFromObject(child, ii.object)) {return ii;}}return null;}ItemInfo infoForAnyChild(View child) {ViewParent parent;while ((parent = child.getParent()) != this) {if (parent == null || !(parent instanceof View)) {return null;}child = (View) parent;}return infoForChild(child);}@Overrideprotected void onAttachedToWindow() {super.onAttachedToWindow();mFirstLayout = true;}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {// For simple implementation, or internal size is always 0.// We depend on the container to specify the layout size of// our view. We can't really know what it is since we will be// adding and removing different arbitrary views and do not// want the layout to change as this happens.setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),getDefaultSize(0, heightMeasureSpec));// Children are just made to fill our space.mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth()- getPaddingLeft() - getPaddingRight(), MeasureSpec.EXACTLY);mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredHeight() - getPaddingTop() - getPaddingBottom(),MeasureSpec.EXACTLY);// Make sure we have created all fragments that we need to have shown.mInLayout = true;populate();mInLayout = false;// Make sure all children have been properly measured.final int size = getChildCount();for (int i = 0; i < size; ++i) {final View child = getChildAt(i);if (child.getVisibility() != GONE) {if (DEBUG)Log.v(TAG, "Measuring #" + i + " " + child + ": "+ mChildWidthMeasureSpec);child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec);}}}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);// Make sure scroll position is set correctly.if (w != oldw) {recomputeScrollPosition(w, oldw, mPageMargin, mPageMargin);}}private void recomputeScrollPosition(int width, int oldWidth, int margin,int oldMargin) {final int widthWithMargin = width + margin;if (oldWidth > 0) {final int oldScrollPos = getScrollX();final int oldwwm = oldWidth + oldMargin;final int oldScrollItem = oldScrollPos / oldwwm;final float scrollOffset = (float) (oldScrollPos % oldwwm) / oldwwm;final int scrollPos = (int) ((oldScrollItem + scrollOffset) * widthWithMargin);scrollTo(scrollPos, getScrollY());if (!mScroller.isFinished()) {// We now return to your regularly scheduled scroll, already in// progress.final int newDuration = mScroller.getDuration()- mScroller.timePassed();mScroller.startScroll(scrollPos, 0, mCurItem * widthWithMargin,0, newDuration);}} else {int scrollPos = mCurItem * widthWithMargin;if (scrollPos != getScrollX()) {completeScroll();scrollTo(scrollPos, getScrollY());}}}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {mInLayout = true;populate();mInLayout = false;final int count = getChildCount();final int width = r - l;for (int i = 0; i < count; i++) {View child = getChildAt(i);ItemInfo ii;if (child.getVisibility() != GONE&& (ii = infoForChild(child)) != null) {int loff = (width + mPageMargin) * ii.position;int childLeft = getPaddingLeft() + loff;int childTop = getPaddingTop();if (DEBUG)Log.v(TAG,"Positioning #" + i + " " + child + " f="+ ii.object + ":" + childLeft + ","+ childTop + " " + child.getMeasuredWidth()+ "x" + child.getMeasuredHeight());child.layout(childLeft, childTop,childLeft + child.getMeasuredWidth(),childTop + child.getMeasuredHeight());}}mFirstLayout = false;}@Overridepublic void computeScroll() {if (DEBUG)Log.i(TAG, "computeScroll: finished=" + mScroller.isFinished());if (!mScroller.isFinished()) {if (mScroller.computeScrollOffset()) {if (DEBUG)Log.i(TAG, "computeScroll: still scrolling");int oldX = getScrollX();int oldY = getScrollY();int x = mScroller.getCurrX();int y = mScroller.getCurrY();if (oldX != x || oldY != y) {scrollTo(x, y);}if (mOnPageChangeListener != null) {final int widthWithMargin = getWidth() + mPageMargin;final int position = x / widthWithMargin;final int offsetPixels = x % widthWithMargin;final float offset = (float) offsetPixels / widthWithMargin;mOnPageChangeListener.onPageScrolled(position, offset,offsetPixels);}// Keep on drawing until the animation has finished.invalidate();return;}}// Done with scroll, clean up state.completeScroll();}private void completeScroll() {boolean needPopulate = mScrolling;if (needPopulate) {// Done with scroll, no longer want to cache view drawing.setScrollingCacheEnabled(false);mScroller.abortAnimation();int oldX = getScrollX();int oldY = getScrollY();int x = mScroller.getCurrX();int y = mScroller.getCurrY();if (oldX != x || oldY != y) {scrollTo(x, y);}setScrollState(SCROLL_STATE_IDLE);}mPopulatePending = false;mScrolling = false;for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if (ii.scrolling) {needPopulate = true;ii.scrolling = false;}}if (needPopulate) {populate();}}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {/* * This method JUST determines whether we want to intercept the motion. * If we return true, onMotionEvent will be called and we do the actual * scrolling there. */final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;// Always take care of the touch gesture being complete.if (action == MotionEvent.ACTION_CANCEL|| action == MotionEvent.ACTION_UP) {// Release the drag.if (DEBUG)Log.v(TAG, "Intercept done!");mIsBeingDragged = false;mIsUnableToDrag = false;mActivePointerId = INVALID_POINTER;return false;}// Nothing more to do here if we have decided whether or not we// are dragging.if (action != MotionEvent.ACTION_DOWN) {if (mIsBeingDragged) {if (DEBUG)Log.v(TAG, "Intercept returning true!");return true;}if (mIsUnableToDrag) {if (DEBUG)Log.v(TAG, "Intercept returning false!");return false;}}switch (action) {case MotionEvent.ACTION_MOVE: {/* * mIsBeingDragged == false, otherwise the shortcut would have * caught it. Check whether the user has moved far enough from his * original down touch. *//* * Locally do absolute value. mLastMotionY is set to the y value of * the down event. */final int activePointerId = mActivePointerId;if (activePointerId == INVALID_POINTER) {// If we don't have a valid id, the touch down wasn't on// content.break;}final int pointerIndex = MotionEventCompat.findPointerIndex(ev,activePointerId);final float x = MotionEventCompat.getX(ev, pointerIndex);final float dx = x - mLastMotionX;final float xDiff = Math.abs(dx);final float y = MotionEventCompat.getY(ev, pointerIndex);final float yDiff = Math.abs(y - mLastMotionY);final int scrollX = getScrollX();final boolean atEdge = (dx > 0 && scrollX == 0)|| (dx < 0 && mAdapter != null && scrollX >= (mAdapter.getCount() - 1) * getWidth() - 1);if (DEBUG)Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + ","+ yDiff);if (canScroll(this, false, (int) dx, (int) x, (int) y)) {// Nested view has scrollable area under this point. Let it be// handled there.mInitialMotionX = mLastMotionX = x;mLastMotionY = y;return false;}if (xDiff > mTouchSlop && xDiff > yDiff) {if (DEBUG)Log.v(TAG, "Starting drag!");mIsBeingDragged = true;setScrollState(SCROLL_STATE_DRAGGING);mLastMotionX = x;setScrollingCacheEnabled(true);} else {if (yDiff > mTouchSlop) {// The finger has moved enough in the vertical// direction to be counted as a drag... abort// any attempt to drag horizontally, to work correctly// with children that have scrolling containers.if (DEBUG)Log.v(TAG, "Starting unable to drag!");mIsUnableToDrag = true;}}break;}case MotionEvent.ACTION_DOWN: {/* * Remember location of down touch. ACTION_DOWN always refers to * pointer index 0. */mLastMotionX = mInitialMotionX = ev.getX();mLastMotionY = ev.getY();mActivePointerId = MotionEventCompat.getPointerId(ev, 0);if (mScrollState == SCROLL_STATE_SETTLING) {// Let the user 'catch' the pager as it animates.mIsBeingDragged = true;mIsUnableToDrag = false;setScrollState(SCROLL_STATE_DRAGGING);} else {completeScroll();mIsBeingDragged = false;mIsUnableToDrag = false;}if (DEBUG)Log.v(TAG, "Down at " + mLastMotionX + "," + mLastMotionY+ " mIsBeingDragged=" + mIsBeingDragged+ "mIsUnableToDrag=" + mIsUnableToDrag);break;}case MotionEventCompat.ACTION_POINTER_UP:onSecondaryPointerUp(ev);break;}/* * The only time we want to intercept motion events is if we are in the * drag mode. */return mIsBeingDragged;}@Overridepublic boolean onTouchEvent(MotionEvent ev) {if (mFakeDragging) {// A fake drag is in progress already, ignore this real one// but still eat the touch events.// (It is likely that the user is multi-touching the screen.)return true;}if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {// Don't handle edge touches immediately -- they may actually belong// to one of our// descendants.return false;}if (mAdapter == null || mAdapter.getCount() == 0) {// Nothing to present or scroll; nothing to touch.return false;}if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);final int action = ev.getAction();boolean needsInvalidate = false;switch (action & MotionEventCompat.ACTION_MASK) {case MotionEvent.ACTION_DOWN: {/* * If being flinged and user touches, stop the fling. isFinished * will be false if being flinged. */completeScroll();// Remember where the motion event startedmLastMotionX = mInitialMotionX = ev.getX();mActivePointerId = MotionEventCompat.getPointerId(ev, 0);break;}case MotionEvent.ACTION_MOVE:if (!mIsBeingDragged) {final int pointerIndex = MotionEventCompat.findPointerIndex(ev,mActivePointerId);final float x = MotionEventCompat.getX(ev, pointerIndex);final float xDiff = Math.abs(x - mLastMotionX);final float y = MotionEventCompat.getY(ev, pointerIndex);final float yDiff = Math.abs(y - mLastMotionY);if (DEBUG)Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff+ "," + yDiff);if (xDiff > mTouchSlop && xDiff > yDiff) {if (DEBUG)Log.v(TAG, "Starting drag!");mIsBeingDragged = true;mLastMotionX = x;setScrollState(SCROLL_STATE_DRAGGING);setScrollingCacheEnabled(true);}}if (mIsBeingDragged) {// Scroll to follow the motion eventfinal int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);final float x = MotionEventCompat.getX(ev, activePointerIndex);final float deltaX = mLastMotionX - x;mLastMotionX = x;float oldScrollX = getScrollX();float scrollX = oldScrollX + deltaX;final int width = getWidth();final int widthWithMargin = width + mPageMargin;final int lastItemIndex = mAdapter.getCount() - 1;final float leftBound = Math.max(0, (mCurItem - 1)* widthWithMargin);final float rightBound = Math.min(mCurItem + 1, lastItemIndex)* widthWithMargin;if (scrollX < leftBound) {if (leftBound == 0) {float over = -scrollX;needsInvalidate = mLeftEdge.onPull(over / width);}scrollX = leftBound;} else if (scrollX > rightBound) {if (rightBound == lastItemIndex * widthWithMargin) {float over = scrollX - rightBound;needsInvalidate = mRightEdge.onPull(over / width);}scrollX = rightBound;}// Don't lose the rounded componentmLastMotionX += scrollX - (int) scrollX;scrollTo((int) scrollX, getScrollY());if (mOnPageChangeListener != null) {final int position = (int) scrollX / widthWithMargin;final int positionOffsetPixels = (int) scrollX% widthWithMargin;final float positionOffset = (float) positionOffsetPixels/ widthWithMargin;mOnPageChangeListener.onPageScrolled(position,positionOffset, positionOffsetPixels);}}break;case MotionEvent.ACTION_UP:if (mIsBeingDragged) {final VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(velocityTracker, mActivePointerId);mPopulatePending = true;final int widthWithMargin = getWidth() + mPageMargin;final int scrollX = getScrollX();final int currentPage = scrollX / widthWithMargin;int nextPage = initialVelocity > 0 ? currentPage: currentPage + 1;setCurrentItemInternal(nextPage, true, true, initialVelocity);mActivePointerId = INVALID_POINTER;endDrag();needsInvalidate = mLeftEdge.onRelease()| mRightEdge.onRelease();}break;case MotionEvent.ACTION_CANCEL:if (mIsBeingDragged) {setCurrentItemInternal(mCurItem, true, true);mActivePointerId = INVALID_POINTER;endDrag();needsInvalidate = mLeftEdge.onRelease()| mRightEdge.onRelease();}break;case MotionEventCompat.ACTION_POINTER_DOWN: {final int index = MotionEventCompat.getActionIndex(ev);final float x = MotionEventCompat.getX(ev, index);mLastMotionX = x;mActivePointerId = MotionEventCompat.getPointerId(ev, index);break;}case MotionEventCompat.ACTION_POINTER_UP:onSecondaryPointerUp(ev);mLastMotionX = MotionEventCompat.getX(ev,MotionEventCompat.findPointerIndex(ev, mActivePointerId));break;}if (needsInvalidate) {invalidate();}return true;}@Overridepublic void draw(Canvas canvas) {super.draw(canvas);boolean needsInvalidate = false;final int overScrollMode = ViewCompat.getOverScrollMode(this);if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS|| (overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS&& mAdapter != null && mAdapter.getCount() > 1)) {if (!mLeftEdge.isFinished()) {final int restoreCount = canvas.save();final int height = getHeight() - getPaddingTop()- getPaddingBottom();canvas.rotate(270);canvas.translate(-height + getPaddingTop(), 0);mLeftEdge.setSize(height, getWidth());needsInvalidate |= mLeftEdge.draw(canvas);canvas.restoreToCount(restoreCount);}if (!mRightEdge.isFinished()) {final int restoreCount = canvas.save();final int width = getWidth();final int height = getHeight() - getPaddingTop()- getPaddingBottom();final int itemCount = mAdapter != null ? mAdapter.getCount(): 1;canvas.rotate(90);canvas.translate(-getPaddingTop(), -itemCount* (width + mPageMargin) + mPageMargin);mRightEdge.setSize(height, width);needsInvalidate |= mRightEdge.draw(canvas);canvas.restoreToCount(restoreCount);}} else {mLeftEdge.finish();mRightEdge.finish();}if (needsInvalidate) {// Keep animatinginvalidate();}}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);// Draw the margin drawable if needed.if (mPageMargin > 0 && mMarginDrawable != null) {final int scrollX = getScrollX();final int width = getWidth();final int offset = scrollX % (width + mPageMargin);if (offset != 0) {// Pages fit completely when settled; we only need to draw when// in betweenfinal int left = scrollX - offset + width;mMarginDrawable.setBounds(left, 0, left + mPageMargin,getHeight());mMarginDrawable.draw(canvas);}}}/** * Start a fake drag of the pager. *  * <p> * A fake drag can be useful if you want to synchronize the motion of the * ViewPager with the touch scrolling of another view, while still letting * the ViewPager control the snapping motion and fling behavior. (e.g. * parallax-scrolling tabs.) Call {@link #fakeDragBy(float)} to simulate the * actual drag motion. Call {@link #endFakeDrag()} to complete the fake drag * and fling as necessary. *  * <p> * During a fake drag the ViewPager will ignore all touch events. If a real * drag is already in progress, this method will return false. *  * @return true if the fake drag began successfully, false if it could not *         be started. *  * @see #fakeDragBy(float) * @see #endFakeDrag() */public boolean beginFakeDrag() {if (mIsBeingDragged) {return false;}mFakeDragging = true;setScrollState(SCROLL_STATE_DRAGGING);mInitialMotionX = mLastMotionX = 0;if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();} else {mVelocityTracker.clear();}final long time = SystemClock.uptimeMillis();final MotionEvent ev = MotionEvent.obtain(time, time,MotionEvent.ACTION_DOWN, 0, 0, 0);mVelocityTracker.addMovement(ev);ev.recycle();mFakeDragBeginTime = time;return true;}/** * End a fake drag of the pager. *  * @see #beginFakeDrag() * @see #fakeDragBy(float) */public void endFakeDrag() {if (!mFakeDragging) {throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");}final VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);mPopulatePending = true;if ((Math.abs(initialVelocity) > mMinimumVelocity)|| Math.abs(mInitialMotionX - mLastMotionX) >= (getWidth() / 3)) {if (mLastMotionX > mInitialMotionX) {setCurrentItemInternal(mCurItem - 1, true, true);} else {setCurrentItemInternal(mCurItem + 1, true, true);}} else {setCurrentItemInternal(mCurItem, true, true);}endDrag();mFakeDragging = false;}/** * Fake drag by an offset in pixels. You must have called * {@link #beginFakeDrag()} first. *  * @param xOffset *            Offset in pixels to drag by. * @see #beginFakeDrag() * @see #endFakeDrag() */public void fakeDragBy(float xOffset) {if (!mFakeDragging) {throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");}mLastMotionX += xOffset;float scrollX = getScrollX() - xOffset;final int width = getWidth();final int widthWithMargin = width + mPageMargin;final float leftBound = Math.max(0, (mCurItem - 1) * widthWithMargin);final float rightBound = Math.min(mCurItem + 1, mAdapter.getCount() - 1) * widthWithMargin;if (scrollX < leftBound) {scrollX = leftBound;} else if (scrollX > rightBound) {scrollX = rightBound;}// Don't lose the rounded componentmLastMotionX += scrollX - (int) scrollX;scrollTo((int) scrollX, getScrollY());if (mOnPageChangeListener != null) {final int position = (int) scrollX / widthWithMargin;final int positionOffsetPixels = (int) scrollX % widthWithMargin;final float positionOffset = (float) positionOffsetPixels/ widthWithMargin;mOnPageChangeListener.onPageScrolled(position, positionOffset,positionOffsetPixels);}// Synthesize an event for the VelocityTracker.final long time = SystemClock.uptimeMillis();final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time,MotionEvent.ACTION_MOVE, mLastMotionX, 0, 0);mVelocityTracker.addMovement(ev);ev.recycle();}/** * Returns true if a fake drag is in progress. *  * @return true if currently in a fake drag, false otherwise. *  * @see #beginFakeDrag() * @see #fakeDragBy(float) * @see #endFakeDrag() */public boolean isFakeDragging() {return mFakeDragging;}private void onSecondaryPointerUp(MotionEvent ev) {final int pointerIndex = MotionEventCompat.getActionIndex(ev);final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);if (pointerId == mActivePointerId) {// This was our active pointer going up. Choose a new// active pointer and adjust accordingly.final int newPointerIndex = pointerIndex == 0 ? 1 : 0;mLastMotionX = MotionEventCompat.getX(ev, newPointerIndex);mActivePointerId = MotionEventCompat.getPointerId(ev,newPointerIndex);if (mVelocityTracker != null) {mVelocityTracker.clear();}}}private void endDrag() {mIsBeingDragged = false;mIsUnableToDrag = false;if (mVelocityTracker != null) {mVelocityTracker.recycle();mVelocityTracker = null;}}private void setScrollingCacheEnabled(boolean enabled) {if (mScrollingCacheEnabled != enabled) {mScrollingCacheEnabled = enabled;if (USE_CACHE) {final int size = getChildCount();for (int i = 0; i < size; ++i) {final View child = getChildAt(i);if (child.getVisibility() != GONE) {child.setDrawingCacheEnabled(enabled);}}}}}/** * Tests scrollability within child views of v given a delta of dx. *  * @param v *            View to test for horizontal scrollability * @param checkV *            Whether the view v passed should itself be checked for *            scrollability (true), or just its children (false). * @param dx *            Delta scrolled in pixels * @param x *            X coordinate of the active touch point * @param y *            Y coordinate of the active touch point * @return true if child views of v can be scrolled by delta of dx. */protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {if (v instanceof ViewGroup) {final ViewGroup group = (ViewGroup) v;final int scrollX = v.getScrollX();final int scrollY = v.getScrollY();final int count = group.getChildCount();// Count backwards - let topmost views consume scroll distance// first.for (int i = count - 1; i >= 0; i--) {// TODO: Add versioned support here for transformed views.// This will not work for transformed views in Honeycomb+final View child = group.getChildAt(i);if (x + scrollX >= child.getLeft()&& x + scrollX < child.getRight()&& y + scrollY >= child.getTop()&& y + scrollY < child.getBottom()&& canScroll(child, true, dx,x + scrollX - child.getLeft(), y + scrollY- child.getTop())) {return true;}}}return checkV && ViewCompat.canScrollHorizontally(v, -dx);}@Overridepublic boolean dispatchKeyEvent(KeyEvent event) {// Let the focused view and/or our descendants get the key firstreturn super.dispatchKeyEvent(event) || executeKeyEvent(event);}/** * You can call this function yourself to have the scroll view perform * scrolling from a key event, just as if the event had been dispatched to * it by the view hierarchy. *  * @param event *            The key event to execute. * @return Return true if the event was handled, else false. */public boolean executeKeyEvent(KeyEvent event) {boolean handled = false;if (event.getAction() == KeyEvent.ACTION_DOWN) {switch (event.getKeyCode()) {case KeyEvent.KEYCODE_DPAD_LEFT:handled = arrowScroll(FOCUS_LEFT);break;case KeyEvent.KEYCODE_DPAD_RIGHT:handled = arrowScroll(FOCUS_RIGHT);break;case KeyEvent.KEYCODE_TAB:if (KeyEventCompat.hasNoModifiers(event)) {handled = arrowScroll(FOCUS_FORWARD);} else if (KeyEventCompat.hasModifiers(event,KeyEvent.META_SHIFT_ON)) {handled = arrowScroll(FOCUS_BACKWARD);}break;}}return handled;}public boolean arrowScroll(int direction) {View currentFocused = findFocus();if (currentFocused == this)currentFocused = null;boolean handled = false;View nextFocused = FocusFinder.getInstance().findNextFocus(this,currentFocused, direction);if (nextFocused != null && nextFocused != currentFocused) {if (direction == View.FOCUS_LEFT) {// If there is nothing to the left, or this is causing us to// jump to the right, then what we really want to do is page// left.if (currentFocused != null&& nextFocused.getLeft() >= currentFocused.getLeft()) {handled = pageLeft();} else {handled = nextFocused.requestFocus();}} else if (direction == View.FOCUS_RIGHT) {// If there is nothing to the right, or this is causing us to// jump to the left, then what we really want to do is page// right.if (currentFocused != null&& nextFocused.getLeft() <= currentFocused.getLeft()) {handled = pageRight();} else {handled = nextFocused.requestFocus();}}} else if (direction == FOCUS_LEFT || direction == FOCUS_BACKWARD) {// Trying to move left and nothing there; try to page.handled = pageLeft();} else if (direction == FOCUS_RIGHT || direction == FOCUS_FORWARD) {// Trying to move right and nothing there; try to page.handled = pageRight();}if (handled) {playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));}return handled;}boolean pageLeft() {if (mCurItem > 0) {setCurrentItem(mCurItem - 1, true);return true;}return false;}boolean pageRight() {if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {setCurrentItem(mCurItem + 1, true);return true;}return false;}/** * We only want the current page that is being shown to be focusable. */@Overridepublic void addFocusables(ArrayList<View> views, int direction,int focusableMode) {final int focusableCount = views.size();final int descendantFocusability = getDescendantFocusability();if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {for (int i = 0; i < getChildCount(); i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {child.addFocusables(views, direction, focusableMode);}}}}// we add ourselves (if focusable) in all cases except for when we are// FOCUS_AFTER_DESCENDANTS and there are some descendants focusable.// this is// to avoid the focus search finding layouts when a more precise search// among the focusable children would be more interesting.if (descendantFocusability != FOCUS_AFTER_DESCENDANTS ||// No focusable descendants(focusableCount == views.size())) {// Note that we can't call the superclass here, because it will// add all views in. So we need to do the same thing View does.if (!isFocusable()) {return;}if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE&& isInTouchMode() && !isFocusableInTouchMode()) {return;}if (views != null) {views.add(this);}}}/** * We only want the current page that is being shown to be touchable. */@Overridepublic void addTouchables(ArrayList<View> views) {// Note that we don't call super.addTouchables(), which means that// we don't call View.addTouchables(). This is okay because a ViewPager// is itself not touchable.for (int i = 0; i < getChildCount(); i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {child.addTouchables(views);}}}}/** * We only want the current page that is being shown to be focusable. */@Overrideprotected boolean onRequestFocusInDescendants(int direction,Rect previouslyFocusedRect) {int index;int increment;int end;int count = getChildCount();if ((direction & FOCUS_FORWARD) != 0) {index = 0;increment = 1;end = count;} else {index = count - 1;increment = -1;end = -1;}for (int i = index; i != end; i += increment) {View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {if (child.requestFocus(direction, previouslyFocusedRect)) {return true;}}}}return false;}@Overridepublic boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {// ViewPagers should only report accessibility info for the current// page,// otherwise things get very confusing.// TODO: Should this note something about the paging container?final int childCount = getChildCount();for (int i = 0; i < childCount; i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {final ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem&& child.dispatchPopulateAccessibilityEvent(event)) {return true;}}}return false;}private class PagerObserver extends DataSetObserver {@Overridepublic void onChanged() {dataSetChanged();}@Overridepublic void onInvalidated() {dataSetChanged();}}}

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