Java tutorial
/* * Copyright (C) 2011 The Android Open Source Project * Copyright (C) 2011 Jake Wharton * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.coleman.demo.view.page; import java.util.ArrayList; import android.content.Context; import android.os.Build; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.os.ParcelableCompat; import android.support.v4.os.ParcelableCompatCreatorCallbacks; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.PagerAdapter; import android.support.v4.view.VelocityTrackerCompat; import android.support.v4.view.VerticalViewPagerCompat; import android.support.v4.view.ViewConfigurationCompat; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.widget.Scroller; /** * Layout manager that allows the user to flip horizontally or vertically * through pages of data. You supply an implementation of a {@link 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 DirectionalViewPager extends ViewPager { private static final String TAG = "DirectionalViewPager"; private static final String XML_NS = "http://schemas.android.com/apk/res/android"; private static final boolean DEBUG = false; private static final boolean USE_CACHE = false; public static final int HORIZONTAL = 0; public static final int VERTICAL = 1; static class ItemInfo { Object object; int position; boolean scrolling; } 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 VerticalViewPagerCompat.DataSetObserver mObserver; private int mChildWidthMeasureSpec; private int mChildHeightMeasureSpec; private boolean mInLayout; private boolean mScrollingCacheEnabled; private boolean mPopulatePending; private boolean mScrolling; private boolean mIsBeingDragged; private boolean mIsUnableToDrag; private int mTouchSlop; private float mInitialMotion; /** * Position of the last motion event. */ private float mLastMotionX; private float mLastMotionY; private int mOrientation = HORIZONTAL; /** * 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 OnPageChangeListener mOnPageChangeListener; private int mScrollState = SCROLL_STATE_IDLE; public DirectionalViewPager(Context context) { super(context); initViewPager(); } public DirectionalViewPager(Context context, AttributeSet attrs) { super(context, attrs); initViewPager(); // We default to horizontal, only change if a value is explicitly // specified int orientation = attrs.getAttributeIntValue(XML_NS, "orientation", -1); if (orientation != -1) { setOrientation(orientation); } } void initViewPager() { setWillNotDraw(false); mScroller = new Scroller(getContext()); final ViewConfiguration configuration = ViewConfiguration.get(getContext()); mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration); mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); } 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) { VerticalViewPagerCompat.setDataSetObserver(mAdapter, null); } mAdapter = adapter; if (mAdapter != null) { if (mObserver == null) { mObserver = new DataSetObserver(); } VerticalViewPagerCompat.setDataSetObserver(mAdapter, 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; } public void setCurrentItem(int item) { mPopulatePending = false; setCurrentItemInternal(item, true, false); } void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) { 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; } if (item > (mCurItem + 1) || item < (mCurItem - 1)) { // 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(); if (smoothScroll) { if (mOrientation == HORIZONTAL) { smoothScrollTo(getWidth() * item, 0); } else { smoothScrollTo(0, getHeight() * item); } if (dispatchSelected && mOnPageChangeListener != null) { mOnPageChangeListener.onPageSelected(item); } } else { if (dispatchSelected && mOnPageChangeListener != null) { mOnPageChangeListener.onPageSelected(item); } completeScroll(); if (mOrientation == HORIZONTAL) { scrollTo(getWidth() * item, 0); } else { scrollTo(0, getHeight() * item); } } } public void setOnPageChangeListener(OnPageChangeListener listener) { mOnPageChangeListener = listener; } /** * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. * * @param dx the number of pixels to scroll by on the X axis * @param dy the number of pixels to scroll by on the Y axis */ void smoothScrollTo(int x, int y) { 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(); return; } setScrollingCacheEnabled(true); mScrolling = true; setScrollState(SCROLL_STATE_SETTLING); mScroller.startScroll(sx, sy, dx, dy); 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.isEmpty() && mAdapter.getCount() > 0; 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 range newCurrItem = 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; } } 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 startPos = mCurItem > 0 ? mCurItem - 1 : mCurItem; final int count = mAdapter.getCount(); final int endPos = mCurItem < (count - 1) ? mCurItem + 1 : count - 1; 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); } } mAdapter.finishUpdate(this); } public static class SavedState extends BaseSavedState { int position; Parcelable adapterState; ClassLoader loader; public SavedState(Parcelable superState) { super(superState); } @Override public void writeToParcel(Parcel out, int flags) { super.writeToParcel(out, flags); out.writeInt(position); out.writeParcelable(adapterState, flags); } @Override public String toString() { return "FragmentPager.SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " position=" + position + "}"; } public static final Parcelable.Creator<SavedState> CREATOR = ParcelableCompat .newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() { @Override public SavedState createFromParcel(Parcel in, ClassLoader loader) { return new SavedState(in, loader); } @Override public 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; } } @Override public Parcelable onSaveInstanceState() { Parcelable superState = super.onSaveInstanceState(); SavedState ss = new SavedState(superState); ss.position = mCurItem; ss.adapterState = mAdapter.saveState(); return ss; } @Override public 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; } } public int getOrientation() { return mOrientation; } public void setOrientation(int orientation) { switch (orientation) { case HORIZONTAL: case VERTICAL: break; default: throw new IllegalArgumentException("Only HORIZONTAL and VERTICAL are valid orientations."); } if (orientation == mOrientation) { return; } // Complete any scroll we are currently in the middle of completeScroll(); // Reset values mInitialMotion = 0; mLastMotionX = 0; mLastMotionY = 0; if (mVelocityTracker != null) { mVelocityTracker.clear(); } // Adjust scroll for new orientation mOrientation = orientation; if (mOrientation == HORIZONTAL) { scrollTo(mCurItem * getWidth(), 0); } else { scrollTo(0, mCurItem * getHeight()); } requestLayout(); } @Override public void addView(View child, int index, ViewGroup.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; } @Override protected void onAttachedToWindow() { super.onAttachedToWindow(); if (mAdapter != null) { populate(); } } @Override protected 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 + " x " + mChildHeightMeasureSpec); child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec); } } } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); // Make sure scroll position is set correctly. if (mOrientation == HORIZONTAL) { int scrollPos = mCurItem * w; if (scrollPos != getScrollX()) { completeScroll(); scrollTo(scrollPos, getScrollY()); } } else { int scrollPos = mCurItem * h; if (scrollPos != getScrollY()) { completeScroll(); scrollTo(getScrollX(), scrollPos); } } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { mInLayout = true; populate(); mInLayout = false; final int count = getChildCount(); final int size = (mOrientation == HORIZONTAL) ? r - l : b - t; for (int i = 0; i < count; i++) { View child = getChildAt(i); ItemInfo ii; if (child.getVisibility() != GONE && (ii = infoForChild(child)) != null) { int off = size * ii.position; int childLeft = getPaddingLeft(); int childTop = getPaddingTop(); if (mOrientation == HORIZONTAL) { childLeft += off; } else { childTop += off; } 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()); } } } @Override public 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) { int size; int value; if (mOrientation == HORIZONTAL) { size = getWidth(); value = x; } else { size = getHeight(); value = y; } final int position = value / size; final int offsetPixels = value % size; final float offset = (float) offsetPixels / size; 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; if ((needPopulate = mScrolling)) { // 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(); } } @Override public 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 && Build.VERSION.SDK_INT > Build.VERSION_CODES.DONUT) { // 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 y = MotionEventCompat.getY(ev, pointerIndex); final float xDiff = Math.abs(x - mLastMotionX); final float yDiff = Math.abs(y - mLastMotionY); float primaryDiff; float secondaryDiff; if (mOrientation == HORIZONTAL) { primaryDiff = xDiff; secondaryDiff = yDiff; } else { primaryDiff = yDiff; secondaryDiff = xDiff; } if (DEBUG) Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff); if (primaryDiff > mTouchSlop && primaryDiff > secondaryDiff) { if (DEBUG) Log.v(TAG, "Starting drag!"); mIsBeingDragged = true; setScrollState(SCROLL_STATE_DRAGGING); if (mOrientation == HORIZONTAL) { mLastMotionX = x; } else { mLastMotionY = y; } setScrollingCacheEnabled(true); } else { if (secondaryDiff > 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. */ if (mOrientation == HORIZONTAL) { mLastMotionX = mInitialMotion = ev.getX(); mLastMotionY = ev.getY(); } else { mLastMotionX = ev.getX(); mLastMotionY = mInitialMotion = 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; } @Override public boolean onTouchEvent(MotionEvent ev) { 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(); 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 started if (mOrientation == HORIZONTAL) { mLastMotionX = mInitialMotion = ev.getX(); } else { mLastMotionY = mInitialMotion = ev.getY(); } 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 y = MotionEventCompat.getY(ev, pointerIndex); final float xDiff = Math.abs(x - mLastMotionX); final float yDiff = Math.abs(y - mLastMotionY); float primaryDiff; float secondaryDiff; if (mOrientation == HORIZONTAL) { primaryDiff = xDiff; secondaryDiff = yDiff; } else { primaryDiff = yDiff; secondaryDiff = xDiff; } if (DEBUG) Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff); if (primaryDiff > mTouchSlop && primaryDiff > secondaryDiff) { if (DEBUG) Log.v(TAG, "Starting drag!"); mIsBeingDragged = true; if (mOrientation == HORIZONTAL) { mLastMotionX = x; } else { mLastMotionY = y; } setScrollState(SCROLL_STATE_DRAGGING); setScrollingCacheEnabled(true); } } if (mIsBeingDragged) { // Scroll to follow the motion event final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId); final float x = MotionEventCompat.getX(ev, activePointerIndex); final float y = MotionEventCompat.getY(ev, activePointerIndex); int size; float scroll; if (mOrientation == HORIZONTAL) { size = getWidth(); scroll = getScrollX() + (mLastMotionX - x); mLastMotionX = x; } else { size = getHeight(); scroll = getScrollY() + (mLastMotionY - y); mLastMotionY = y; } final float lowerBound = Math.max(0, (mCurItem - 1) * size); final float upperBound = Math.min(mCurItem + 1, mAdapter.getCount() - 1) * size; if (scroll < lowerBound) { scroll = lowerBound; } else if (scroll > upperBound) { scroll = upperBound; } if (mOrientation == HORIZONTAL) { // Don't lose the rounded component mLastMotionX += scroll - (int) scroll; scrollTo((int) scroll, getScrollY()); } else { // Don't lose the rounded component mLastMotionY += scroll - (int) scroll; scrollTo(getScrollX(), (int) scroll); } if (mOnPageChangeListener != null) { final int position = (int) scroll / size; final int positionOffsetPixels = (int) scroll % size; final float positionOffset = (float) positionOffsetPixels / size; mOnPageChangeListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } } break; case MotionEvent.ACTION_UP: if (mIsBeingDragged) { final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int initialVelocity; float lastMotion; int sizeOverThree; if (mOrientation == HORIZONTAL) { initialVelocity = (int) VelocityTrackerCompat.getXVelocity(velocityTracker, mActivePointerId); lastMotion = mLastMotionX; sizeOverThree = getWidth() / 3; } else { initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId); lastMotion = mLastMotionY; sizeOverThree = getHeight() / 3; } mPopulatePending = true; if ((Math.abs(initialVelocity) > mMinimumVelocity) || Math.abs(mInitialMotion - lastMotion) >= sizeOverThree) { if (lastMotion > mInitialMotion) { setCurrentItemInternal(mCurItem - 1, true, true); } else { setCurrentItemInternal(mCurItem + 1, true, true); } } else { setCurrentItemInternal(mCurItem, true, true); } mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEvent.ACTION_CANCEL: if (mIsBeingDragged) { setCurrentItemInternal(mCurItem, true, true); mActivePointerId = INVALID_POINTER; endDrag(); } break; case MotionEventCompat.ACTION_POINTER_DOWN: { final int index = MotionEventCompat.getActionIndex(ev); if (mOrientation == HORIZONTAL) { mLastMotionX = MotionEventCompat.getX(ev, index); } else { mLastMotionY = MotionEventCompat.getY(ev, index); } mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } case MotionEventCompat.ACTION_POINTER_UP: onSecondaryPointerUp(ev); final int index = MotionEventCompat.findPointerIndex(ev, mActivePointerId); if (mOrientation == HORIZONTAL) { mLastMotionX = MotionEventCompat.getX(ev, index); } else { mLastMotionY = MotionEventCompat.getY(ev, index); } break; } return true; } 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; if (mOrientation == HORIZONTAL) { mLastMotionX = MotionEventCompat.getX(ev, newPointerIndex); } else { mLastMotionY = MotionEventCompat.getY(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); } } } } } private class DataSetObserver extends VerticalViewPagerCompat.DataSetObserver { public void onDataSetChanged() { dataSetChanged(); } } }