Java tutorial
/* * 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. */ package com.android.contacts.detail; import android.animation.Animator; import android.animation.Animator.AnimatorListener; import android.animation.ObjectAnimator; import android.app.Activity; import android.app.FragmentManager; import android.app.FragmentTransaction; import android.content.Context; import android.net.Uri; import android.os.Bundle; import android.support.v4.view.ViewPager; import android.support.v4.view.ViewPager.OnPageChangeListener; import android.view.LayoutInflater; import android.view.View; import android.view.ViewPropertyAnimator; import android.view.animation.AnimationUtils; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import com.android.contacts.NfcHandler; import com.android.contacts.R; import com.android.contacts.activities.ContactDetailActivity.FragmentKeyListener; import com.android.contacts.common.model.Contact; import com.android.contacts.util.PhoneCapabilityTester; import com.android.contacts.common.util.UriUtils; import com.android.contacts.widget.FrameLayoutWithOverlay; import com.android.contacts.widget.TransitionAnimationView; /** * Determines the layout of the contact card. */ public class ContactDetailLayoutController { private static final String KEY_CONTACT_URI = "contactUri"; private static final String KEY_CONTACT_HAS_UPDATES = "contactHasUpdates"; private static final String KEY_CURRENT_PAGE_INDEX = "currentPageIndex"; private static final int TAB_INDEX_DETAIL = 0; private static final int TAB_INDEX_UPDATES = 1; private final int SINGLE_PANE_FADE_IN_DURATION = 275; /** * There are 4 possible layouts for the contact detail screen: TWO_COLUMN, * VIEW_PAGER_AND_TAB_CAROUSEL, FRAGMENT_CAROUSEL, and TWO_COLUMN_FRAGMENT_CAROUSEL. */ private interface LayoutMode { /** * Tall and wide screen with details and updates shown side-by-side. */ static final int TWO_COLUMN = 0; /** * Tall and narrow screen to allow swipe between the details and updates. */ static final int VIEW_PAGER_AND_TAB_CAROUSEL = 1; /** * Short and wide screen to allow part of the other page to show. */ static final int FRAGMENT_CAROUSEL = 2; /** * Same as FRAGMENT_CAROUSEL (allowing part of the other page to show) except the details * layout is similar to the details layout in TWO_COLUMN mode. */ static final int TWO_COLUMN_FRAGMENT_CAROUSEL = 3; } private final Activity mActivity; private final LayoutInflater mLayoutInflater; private final FragmentManager mFragmentManager; private final View mViewContainer; private final TransitionAnimationView mTransitionAnimationView; private ContactDetailFragment mDetailFragment; private ContactDetailUpdatesFragment mUpdatesFragment; private View mDetailFragmentView; private View mUpdatesFragmentView; private final ViewPager mViewPager; private ContactDetailViewPagerAdapter mViewPagerAdapter; private int mViewPagerState; private final ContactDetailTabCarousel mTabCarousel; private final ContactDetailFragmentCarousel mFragmentCarousel; private final ContactDetailFragment.Listener mContactDetailFragmentListener; private Contact mContactData; private Uri mContactUri; private boolean mTabCarouselIsAnimating; private boolean mContactHasUpdates; private int mLayoutMode; public ContactDetailLayoutController(Activity activity, Bundle savedState, FragmentManager fragmentManager, TransitionAnimationView animationView, View viewContainer, ContactDetailFragment.Listener contactDetailFragmentListener) { if (fragmentManager == null) { throw new IllegalStateException( "Cannot initialize a ContactDetailLayoutController " + "without a non-null FragmentManager"); } mActivity = activity; mLayoutInflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE); mFragmentManager = fragmentManager; mContactDetailFragmentListener = contactDetailFragmentListener; mTransitionAnimationView = animationView; // Retrieve views in case this is view pager and carousel mode mViewContainer = viewContainer; mViewPager = (ViewPager) viewContainer.findViewById(R.id.pager); mTabCarousel = (ContactDetailTabCarousel) viewContainer.findViewById(R.id.tab_carousel); // Retrieve view in case this is in fragment carousel mode mFragmentCarousel = (ContactDetailFragmentCarousel) viewContainer.findViewById(R.id.fragment_carousel); // Retrieve container views in case they are already in the XML layout mDetailFragmentView = viewContainer.findViewById(R.id.about_fragment_container); mUpdatesFragmentView = viewContainer.findViewById(R.id.updates_fragment_container); // Determine the layout mode based on the presence of certain views in the layout XML. if (mViewPager != null) { mLayoutMode = LayoutMode.VIEW_PAGER_AND_TAB_CAROUSEL; } else if (mFragmentCarousel != null) { if (PhoneCapabilityTester.isUsingTwoPanes(mActivity)) { mLayoutMode = LayoutMode.TWO_COLUMN_FRAGMENT_CAROUSEL; } else { mLayoutMode = LayoutMode.FRAGMENT_CAROUSEL; } } else { mLayoutMode = LayoutMode.TWO_COLUMN; } initialize(savedState); } private void initialize(Bundle savedState) { boolean fragmentsAddedToFragmentManager = true; mDetailFragment = (ContactDetailFragment) mFragmentManager .findFragmentByTag(ContactDetailViewPagerAdapter.ABOUT_FRAGMENT_TAG); mUpdatesFragment = (ContactDetailUpdatesFragment) mFragmentManager .findFragmentByTag(ContactDetailViewPagerAdapter.UPDATES_FRAGMENT_TAG); // If the detail fragment was found in the {@link FragmentManager} then we don't need to add // it again. Otherwise, create the fragments dynamically and remember to add them to the // {@link FragmentManager}. if (mDetailFragment == null) { mDetailFragment = new ContactDetailFragment(); mUpdatesFragment = new ContactDetailUpdatesFragment(); fragmentsAddedToFragmentManager = false; } mDetailFragment.setListener(mContactDetailFragmentListener); NfcHandler.register(mActivity, mDetailFragment); // Read from savedState if possible int currentPageIndex = 0; if (savedState != null) { mContactUri = savedState.getParcelable(KEY_CONTACT_URI); mContactHasUpdates = savedState.getBoolean(KEY_CONTACT_HAS_UPDATES); currentPageIndex = savedState.getInt(KEY_CURRENT_PAGE_INDEX, 0); } switch (mLayoutMode) { case LayoutMode.VIEW_PAGER_AND_TAB_CAROUSEL: { // Inflate 2 view containers to pass in as children to the {@link ViewPager}, // which will in turn be the parents to the mDetailFragment and mUpdatesFragment // since the fragments must have the same parent view IDs in both landscape and // portrait layouts. mDetailFragmentView = mLayoutInflater.inflate(R.layout.contact_detail_about_fragment_container, mViewPager, false); mUpdatesFragmentView = mLayoutInflater.inflate(R.layout.contact_detail_updates_fragment_container, mViewPager, false); mViewPagerAdapter = new ContactDetailViewPagerAdapter(); mViewPagerAdapter.setAboutFragmentView(mDetailFragmentView); mViewPagerAdapter.setUpdatesFragmentView(mUpdatesFragmentView); mViewPager.addView(mDetailFragmentView); mViewPager.addView(mUpdatesFragmentView); mViewPager.setAdapter(mViewPagerAdapter); mViewPager.setOnPageChangeListener(mOnPageChangeListener); if (!fragmentsAddedToFragmentManager) { FragmentTransaction transaction = mFragmentManager.beginTransaction(); transaction.add(R.id.about_fragment_container, mDetailFragment, ContactDetailViewPagerAdapter.ABOUT_FRAGMENT_TAG); transaction.add(R.id.updates_fragment_container, mUpdatesFragment, ContactDetailViewPagerAdapter.UPDATES_FRAGMENT_TAG); transaction.commitAllowingStateLoss(); mFragmentManager.executePendingTransactions(); } mTabCarousel.setListener(mTabCarouselListener); mTabCarousel.restoreCurrentTab(currentPageIndex); mDetailFragment.setVerticalScrollListener(new VerticalScrollListener(TAB_INDEX_DETAIL)); mUpdatesFragment.setVerticalScrollListener(new VerticalScrollListener(TAB_INDEX_UPDATES)); mViewPager.setCurrentItem(currentPageIndex); break; } case LayoutMode.TWO_COLUMN: { if (!fragmentsAddedToFragmentManager) { FragmentTransaction transaction = mFragmentManager.beginTransaction(); transaction.add(R.id.about_fragment_container, mDetailFragment, ContactDetailViewPagerAdapter.ABOUT_FRAGMENT_TAG); transaction.add(R.id.updates_fragment_container, mUpdatesFragment, ContactDetailViewPagerAdapter.UPDATES_FRAGMENT_TAG); transaction.commitAllowingStateLoss(); mFragmentManager.executePendingTransactions(); } break; } case LayoutMode.FRAGMENT_CAROUSEL: case LayoutMode.TWO_COLUMN_FRAGMENT_CAROUSEL: { // Add the fragments to the fragment containers in the carousel using a // {@link FragmentTransaction} if they haven't already been added to the // {@link FragmentManager}. if (!fragmentsAddedToFragmentManager) { FragmentTransaction transaction = mFragmentManager.beginTransaction(); transaction.add(R.id.about_fragment_container, mDetailFragment, ContactDetailViewPagerAdapter.ABOUT_FRAGMENT_TAG); transaction.add(R.id.updates_fragment_container, mUpdatesFragment, ContactDetailViewPagerAdapter.UPDATES_FRAGMENT_TAG); transaction.commitAllowingStateLoss(); mFragmentManager.executePendingTransactions(); } mFragmentCarousel.setFragmentViews((FrameLayoutWithOverlay) mDetailFragmentView, (FrameLayoutWithOverlay) mUpdatesFragmentView); mFragmentCarousel.setCurrentPage(currentPageIndex); break; } } // Setup the layout if we already have a saved state if (savedState != null) { if (mContactHasUpdates) { showContactWithUpdates(false); } else { showContactWithoutUpdates(); } } } public void setContactData(Contact data) { final boolean contactWasLoaded; final boolean contactHadUpdates; final boolean isDifferentContact; if (mContactData == null) { contactHadUpdates = false; contactWasLoaded = false; isDifferentContact = true; } else { contactHadUpdates = mContactHasUpdates; contactWasLoaded = true; isDifferentContact = !UriUtils.areEqual(mContactData.getLookupUri(), data.getLookupUri()); } mContactData = data; if (PhoneCapabilityTester.isUsingTwoPanes(mActivity)) { // Tablet: If we already showed data before, we want to cross-fade from screen to screen if (contactWasLoaded && mTransitionAnimationView != null && isDifferentContact) { mTransitionAnimationView.startMaskTransition(mContactData == null, -1); } } else { // Small screen: We are on our own screen. Fade the data in, but only the first time if (!contactWasLoaded) { mViewContainer.setAlpha(0.0f); final ViewPropertyAnimator animator = mViewContainer.animate(); animator.alpha(1.0f); animator.setDuration(SINGLE_PANE_FADE_IN_DURATION); } } showContactWithoutUpdates(); } public void showEmptyState() { switch (mLayoutMode) { case LayoutMode.FRAGMENT_CAROUSEL: { mFragmentCarousel.setCurrentPage(0); mFragmentCarousel.enableSwipe(false); mDetailFragment.showEmptyState(); break; } case LayoutMode.TWO_COLUMN: { mDetailFragment.setShowStaticPhoto(false); mUpdatesFragmentView.setVisibility(View.GONE); mDetailFragment.showEmptyState(); break; } case LayoutMode.TWO_COLUMN_FRAGMENT_CAROUSEL: { mFragmentCarousel.setCurrentPage(0); mFragmentCarousel.enableSwipe(false); mDetailFragment.setShowStaticPhoto(false); mUpdatesFragmentView.setVisibility(View.GONE); mDetailFragment.showEmptyState(); break; } case LayoutMode.VIEW_PAGER_AND_TAB_CAROUSEL: { mDetailFragment.setShowStaticPhoto(false); mDetailFragment.showEmptyState(); mTabCarousel.loadData(null); mTabCarousel.setVisibility(View.GONE); mViewPagerAdapter.enableSwipe(false); mViewPager.setCurrentItem(0); break; } default: throw new IllegalStateException("Invalid LayoutMode " + mLayoutMode); } } /** * Setup the layout for the contact with updates. * TODO: Clean up this method so it's easier to understand. */ private void showContactWithUpdates(boolean animateStateChange) { if (mContactData == null) { return; } Uri previousContactUri = mContactUri; mContactUri = mContactData.getLookupUri(); boolean isDifferentContact = !UriUtils.areEqual(previousContactUri, mContactUri); switch (mLayoutMode) { case LayoutMode.TWO_COLUMN: { if (!isDifferentContact && animateStateChange) { // This is screen is very hard to animate properly, because there is such a hard // cut from the regular version. A proper animation would have to reflow text // and move things around. Doing a simple cross-fade instead. mTransitionAnimationView.startMaskTransition(false, -1); } // Set the contact data (hide the static photo because the photo will already be in // the header that scrolls with contact details). mDetailFragment.setShowStaticPhoto(false); // Show the updates fragment mUpdatesFragmentView.setVisibility(View.VISIBLE); break; } case LayoutMode.VIEW_PAGER_AND_TAB_CAROUSEL: { // Update and show the tab carousel (also restore its last saved position) mTabCarousel.loadData(mContactData); mTabCarousel.restoreYCoordinate(); mTabCarousel.setVisibility(View.VISIBLE); // Update ViewPager to allow swipe between all the fragments (to see updates) mViewPagerAdapter.enableSwipe(true); // If this is a different contact than before, then reset some views. if (isDifferentContact) { resetViewPager(); resetTabCarousel(); } if (!isDifferentContact && animateStateChange) { mTabCarousel.animateAppear(mViewContainer.getWidth(), mDetailFragment.getFirstListItemOffset()); } break; } case LayoutMode.FRAGMENT_CAROUSEL: { // Allow swiping between all fragments mFragmentCarousel.enableSwipe(true); if (!isDifferentContact && animateStateChange) { mFragmentCarousel.animateAppear(); } break; } case LayoutMode.TWO_COLUMN_FRAGMENT_CAROUSEL: { // Allow swiping between all fragments mFragmentCarousel.enableSwipe(true); if (isDifferentContact) { mFragmentCarousel.reset(); } if (!isDifferentContact && animateStateChange) { mFragmentCarousel.animateAppear(); } mDetailFragment.setShowStaticPhoto(false); break; } default: throw new IllegalStateException("Invalid LayoutMode " + mLayoutMode); } if (isDifferentContact) { resetFragments(); } mDetailFragment.setData(mContactUri, mContactData); mUpdatesFragment.setData(mContactUri, mContactData); } /** * Setup the layout for the contact without updates. * TODO: Clean up this method so it's easier to understand. */ private void showContactWithoutUpdates() { if (mContactData == null) { return; } Uri previousContactUri = mContactUri; mContactUri = mContactData.getLookupUri(); boolean isDifferentContact = !UriUtils.areEqual(previousContactUri, mContactUri); switch (mLayoutMode) { case LayoutMode.TWO_COLUMN: // Show the static photo which is next to the list of scrolling contact details mDetailFragment.setShowStaticPhoto(true); // Hide the updates fragment mUpdatesFragmentView.setVisibility(View.GONE); break; case LayoutMode.VIEW_PAGER_AND_TAB_CAROUSEL: // Hide the tab carousel mTabCarousel.setVisibility(View.GONE); // Update ViewPager to disable swipe so that it only shows the detail fragment // and switch to the detail fragment mViewPagerAdapter.enableSwipe(false); mViewPager.setCurrentItem(0, false /* smooth transition */); break; case LayoutMode.FRAGMENT_CAROUSEL: // Disable swipe so only the detail fragment shows mFragmentCarousel.setCurrentPage(0); mFragmentCarousel.enableSwipe(false); break; case LayoutMode.TWO_COLUMN_FRAGMENT_CAROUSEL: mFragmentCarousel.setCurrentPage(0); mFragmentCarousel.enableSwipe(false); mDetailFragment.setShowStaticPhoto(true); break; default: throw new IllegalStateException("Invalid LayoutMode " + mLayoutMode); } if (isDifferentContact) { resetFragments(); } mDetailFragment.setData(mContactUri, mContactData); } private void resetTabCarousel() { mTabCarousel.reset(); } private void resetViewPager() { mViewPager.setCurrentItem(0, false /* smooth transition */); } private void resetFragments() { mDetailFragment.resetAdapter(); mUpdatesFragment.resetAdapter(); } public FragmentKeyListener getCurrentPage() { switch (getCurrentPageIndex()) { case 0: return mDetailFragment; case 1: return mUpdatesFragment; default: throw new IllegalStateException("Invalid current item for ViewPager"); } } private int getCurrentPageIndex() { // If the contact has social updates, then retrieve the current page based on the // {@link ViewPager} or fragment carousel. if (mContactHasUpdates) { if (mViewPager != null) { return mViewPager.getCurrentItem(); } else if (mFragmentCarousel != null) { return mFragmentCarousel.getCurrentPage(); } } // Otherwise return the default page (detail fragment). return 0; } public void onSaveInstanceState(Bundle outState) { outState.putParcelable(KEY_CONTACT_URI, mContactUri); outState.putBoolean(KEY_CONTACT_HAS_UPDATES, mContactHasUpdates); outState.putInt(KEY_CURRENT_PAGE_INDEX, getCurrentPageIndex()); } private final OnPageChangeListener mOnPageChangeListener = new OnPageChangeListener() { private ObjectAnimator mTabCarouselAnimator; @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // The user is horizontally dragging the {@link ViewPager}, so send // these scroll changes to the tab carousel. Ignore these events though if the carousel // is actually controlling the {@link ViewPager} scrolls because it will already be // in the correct position. if (mViewPager.isFakeDragging()) return; int x = (int) ((position + positionOffset) * mTabCarousel.getAllowedHorizontalScrollLength()); mTabCarousel.scrollTo(x, 0); } @Override public void onPageSelected(int position) { // Since the {@link ViewPager} has committed to a new page now (but may not have // finished scrolling yet), update the tab selection in the carousel. mTabCarousel.setCurrentTab(position); } @Override public void onPageScrollStateChanged(int state) { if (mViewPagerState == ViewPager.SCROLL_STATE_IDLE) { // If we are leaving the IDLE state, we are starting a swipe. // First cancel any pending animations on the tab carousel. cancelTabCarouselAnimator(); // Sync the two lists because the list on the other page will start to show as // we swipe over more. syncScrollStateBetweenLists(mViewPager.getCurrentItem()); } else if (state == ViewPager.SCROLL_STATE_IDLE) { // Otherwise if the {@link ViewPager} is idle now, a page has been selected and // scrolled into place. Perform an animation of the tab carousel is needed. int currentPageIndex = mViewPager.getCurrentItem(); int tabCarouselOffset = (int) mTabCarousel.getY(); boolean shouldAnimateTabCarousel; // Find the offset position of the first item in the list of the current page. int listOffset = getOffsetOfFirstItemInList(currentPageIndex); // If the list was able to successfully offset by the tab carousel amount, then // log this as the new Y coordinate for that page, and no animation is needed. if (listOffset == tabCarouselOffset) { mTabCarousel.storeYCoordinate(currentPageIndex, tabCarouselOffset); shouldAnimateTabCarousel = false; } else if (listOffset == Integer.MIN_VALUE) { // If the offset of the first item in the list is unknown (i.e. the item // is no longer visible on screen) then just animate the tab carousel to the // previously logged position. shouldAnimateTabCarousel = true; } else if (Math.abs(listOffset) < Math.abs(tabCarouselOffset)) { // If the list could not offset the full amount of the tab carousel offset (i.e. // the list can only be scrolled a tiny amount), then animate the carousel down // to compensate. mTabCarousel.storeYCoordinate(currentPageIndex, listOffset); shouldAnimateTabCarousel = true; } else { // By default, animate back to the Y coordinate of the tab carousel the last // time the other page was selected. shouldAnimateTabCarousel = true; } if (shouldAnimateTabCarousel) { float desiredOffset = mTabCarousel.getStoredYCoordinateForTab(currentPageIndex); if (desiredOffset != tabCarouselOffset) { createTabCarouselAnimator(desiredOffset); mTabCarouselAnimator.start(); } } } mViewPagerState = state; } private void createTabCarouselAnimator(float desiredValue) { mTabCarouselAnimator = ObjectAnimator.ofFloat(mTabCarousel, "y", desiredValue).setDuration(75); mTabCarouselAnimator.setInterpolator( AnimationUtils.loadInterpolator(mActivity, android.R.anim.accelerate_decelerate_interpolator)); mTabCarouselAnimator.addListener(mTabCarouselAnimatorListener); } private void cancelTabCarouselAnimator() { if (mTabCarouselAnimator != null) { mTabCarouselAnimator.cancel(); mTabCarouselAnimator = null; mTabCarouselIsAnimating = false; } } }; private void syncScrollStateBetweenLists(int currentPageIndex) { // Since the user interacted with the currently visible page, we need to sync the // list on the other page (i.e. if the updates page is the current page, modify the // list in the details page). if (currentPageIndex == TAB_INDEX_UPDATES) { mDetailFragment.requestToMoveToOffset((int) mTabCarousel.getY()); } else { mUpdatesFragment.requestToMoveToOffset((int) mTabCarousel.getY()); } } private int getOffsetOfFirstItemInList(int currentPageIndex) { if (currentPageIndex == TAB_INDEX_DETAIL) { return mDetailFragment.getFirstListItemOffset(); } else { return mUpdatesFragment.getFirstListItemOffset(); } } /** * This listener keeps track of whether the tab carousel animation is currently going on or not, * in order to prevent other simultaneous changes to the Y position of the tab carousel which * can cause flicker. */ private final AnimatorListener mTabCarouselAnimatorListener = new AnimatorListener() { @Override public void onAnimationCancel(Animator animation) { mTabCarouselIsAnimating = false; } @Override public void onAnimationEnd(Animator animation) { mTabCarouselIsAnimating = false; } @Override public void onAnimationRepeat(Animator animation) { mTabCarouselIsAnimating = true; } @Override public void onAnimationStart(Animator animation) { mTabCarouselIsAnimating = true; } }; private final ContactDetailTabCarousel.Listener mTabCarouselListener = new ContactDetailTabCarousel.Listener() { @Override public void onTouchDown() { // The user just started scrolling the carousel, so begin // "fake dragging" the {@link ViewPager} if it's not already // doing so. if (!mViewPager.isFakeDragging()) mViewPager.beginFakeDrag(); } @Override public void onTouchUp() { // The user just stopped scrolling the carousel, so stop // "fake dragging" the {@link ViewPager} if it was doing so // before. if (mViewPager.isFakeDragging()) mViewPager.endFakeDrag(); } @Override public void onScrollChanged(int l, int t, int oldl, int oldt) { // The user is scrolling the carousel, so send the scroll // deltas to the {@link ViewPager} so it can move in sync. if (mViewPager.isFakeDragging()) { mViewPager.fakeDragBy(oldl - l); } } @Override public void onTabSelected(int position) { // The user selected a tab, so update the {@link ViewPager} mViewPager.setCurrentItem(position); } }; private final class VerticalScrollListener implements OnScrollListener { private final int mPageIndex; public VerticalScrollListener(int pageIndex) { mPageIndex = pageIndex; } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { int currentPageIndex = mViewPager.getCurrentItem(); // Don't move the carousel if: 1) the contact does not have social updates because then // tab carousel must not be visible, 2) if the view pager is still being scrolled, // 3) if the current page being viewed is not this one, or 4) if the tab carousel // is already being animated vertically. if (!mContactHasUpdates || mViewPagerState != ViewPager.SCROLL_STATE_IDLE || mPageIndex != currentPageIndex || mTabCarouselIsAnimating) { return; } // If the FIRST item is not visible on the screen, then the carousel must be pinned // at the top of the screen. if (firstVisibleItem != 0) { mTabCarousel.moveToYCoordinate(mPageIndex, -mTabCarousel.getAllowedVerticalScrollLength()); return; } View topView = view.getChildAt(firstVisibleItem); if (topView == null) { return; } int amtToScroll = Math.max((int) view.getChildAt(firstVisibleItem).getY(), -mTabCarousel.getAllowedVerticalScrollLength()); mTabCarousel.moveToYCoordinate(mPageIndex, amtToScroll); } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { // Once the list has become IDLE, check if we need to sync the scroll position of // the other list now. This will make swiping faster by doing the re-layout now // (instead of at the start of a swipe). However, there will still be another check // when we start swiping if the scroll positions are correct (to catch the edge case // where the user flings and immediately starts a swipe so we never get the idle state). if (scrollState == SCROLL_STATE_IDLE) { syncScrollStateBetweenLists(mPageIndex); } } } }