Java tutorial
// Copyright 2016 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. package org.chromium.chrome.browser.ntp.cards; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import android.animation.AnimatorSet; import android.animation.ObjectAnimator; import android.content.Context; import android.content.res.Resources; import android.graphics.Region; import android.support.v4.view.animation.FastOutLinearInInterpolator; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.util.AttributeSet; import android.view.GestureDetector; import android.view.MotionEvent; import android.view.View; import android.view.animation.Interpolator; import android.view.inputmethod.EditorInfo; import android.view.inputmethod.InputConnection; import org.chromium.base.Log; import org.chromium.chrome.R; import org.chromium.chrome.browser.ntp.NewTabPageLayout; import org.chromium.chrome.browser.ntp.snippets.SectionHeaderViewHolder; import org.chromium.chrome.browser.ntp.snippets.SnippetArticle; import org.chromium.chrome.browser.util.ViewUtils; import java.util.HashMap; import java.util.Map; /** * Simple wrapper on top of a RecyclerView that will acquire focus when tapped. Ensures the * New Tab page receives focus when clicked. */ public class NewTabPageRecyclerView extends RecyclerView { private static final String TAG = "NtpCards"; private static final Interpolator DISMISS_INTERPOLATOR = new FastOutLinearInInterpolator(); private static final int DISMISS_ANIMATION_TIME_MS = 300; private final GestureDetector mGestureDetector; private final LinearLayoutManager mLayoutManager; private final int mToolbarHeight; private final int mMaxHeaderHeight; /** * Total height of the items being dismissed. Tracked to allow the bottom space to compensate * for their removal animation and avoid moving the scroll position. */ private int mCompensationHeight; /** * Height compensation value for each item being dismissed. Since dismissals sometimes include * sibling elements, and these don't get the standard treatment, we track the total height * associated with the element the user interacted with. */ private final Map<ViewHolder, Integer> mCompensationHeightMap = new HashMap<>(); /** View used to calculate the position of the cards' snap point. */ private View mAboveTheFoldView; /** Whether the RecyclerView and its children should react to touch events. */ private boolean mTouchEnabled = true; /** Whether the above-the-fold left space for a peeking card to be displayed. */ private boolean mHasSpaceForPeekingCard; /** * Constructor needed to inflate from XML. */ public NewTabPageRecyclerView(Context context, AttributeSet attrs) { super(context, attrs); mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() { @Override public boolean onSingleTapUp(MotionEvent e) { boolean retVal = super.onSingleTapUp(e); requestFocus(); return retVal; } }); mLayoutManager = new LinearLayoutManager(getContext()); setLayoutManager(mLayoutManager); Resources res = context.getResources(); mToolbarHeight = res.getDimensionPixelSize(R.dimen.toolbar_height_no_shadow) + res.getDimensionPixelSize(R.dimen.toolbar_progress_bar_height); mMaxHeaderHeight = res.getDimensionPixelSize(R.dimen.snippets_article_header_height); } public boolean isFirstItemVisible() { return mLayoutManager.findFirstVisibleItemPosition() == 0; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { mGestureDetector.onTouchEvent(ev); if (!mTouchEnabled) return true; return super.onInterceptTouchEvent(ev); } public void setTouchEnabled(boolean enabled) { mTouchEnabled = enabled; } @Override public boolean onTouchEvent(MotionEvent ev) { if (!mTouchEnabled) return false; // Action down would already have been handled in onInterceptTouchEvent if (ev.getActionMasked() != MotionEvent.ACTION_DOWN) { mGestureDetector.onTouchEvent(ev); } return super.onTouchEvent(ev); } @Override public void focusableViewAvailable(View v) { // To avoid odd jumps during NTP animation transitions, we do not attempt to give focus // to child views if this scroll view already has focus. if (hasFocus()) return; super.focusableViewAvailable(v); } @Override public InputConnection onCreateInputConnection(EditorInfo outAttrs) { // Fixes landscape transitions when unfocusing the URL bar: crbug.com/288546 outAttrs.imeOptions = EditorInfo.IME_FLAG_NO_FULLSCREEN; return super.onCreateInputConnection(outAttrs); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int numberViews = getChildCount(); for (int i = 0; i < numberViews; ++i) { View view = getChildAt(i); NewTabPageViewHolder viewHolder = (NewTabPageViewHolder) getChildViewHolder(view); if (viewHolder == null) return; viewHolder.updateLayoutParams(); } super.onLayout(changed, l, t, r, b); } public void setAboveTheFoldView(View aboveTheFoldView) { mAboveTheFoldView = aboveTheFoldView; } public void setHasSpaceForPeekingCard(boolean hasSpaceForPeekingCard) { mHasSpaceForPeekingCard = hasSpaceForPeekingCard; } /** Scroll up from the cards' current position and snap to present the first one. */ public void scrollToFirstCard() { // Offset the target scroll by the height of the omnibox (the top padding). final int targetScroll = mAboveTheFoldView.getHeight() - mAboveTheFoldView.getPaddingTop(); // If (somehow) the peeking card is tapped while midway through the transition, // we need to account for how much we have already scrolled. smoothScrollBy(0, targetScroll - computeVerticalScrollOffset()); } /** * Updates the space added at the end of the list to make sure the above/below the fold * distinction can be preserved. */ public void refreshBottomSpacing() { ViewHolder bottomSpacingViewHolder = findBottomSpacer(); // It might not be in the layout yet if it's not visible or ready to be displayed. if (bottomSpacingViewHolder == null) return; assert bottomSpacingViewHolder.getItemViewType() == NewTabPageItem.VIEW_TYPE_SPACING; bottomSpacingViewHolder.itemView.requestLayout(); } /** * Calculates the height of the bottom spacing item, such that there is always enough content * below the fold to push the header up to to the top of the screen. */ int calculateBottomSpacing() { int aboveTheFoldPosition = getNewTabPageAdapter().getAboveTheFoldPosition(); int firstVisiblePos = mLayoutManager.findFirstVisibleItemPosition(); if (aboveTheFoldPosition == RecyclerView.NO_POSITION || firstVisiblePos == RecyclerView.NO_POSITION) { return 0; } // We have enough items to fill the view, since the above-the-fold item is not even visible. if (firstVisiblePos > aboveTheFoldPosition) { return 0; } ViewHolder lastContentItem = findLastContentItem(); ViewHolder aboveTheFold = findViewHolderForAdapterPosition(aboveTheFoldPosition); int bottomSpacing = getHeight() - mToolbarHeight; if (lastContentItem == null || aboveTheFold == null) { // This can happen in several cases, where some elements are not visible and the // RecyclerView didn't already attach them. We handle it by just adding space to make // sure that we never run out and force the UI to jump around and get stuck in a // position that breaks the animations. The height will be properly adjusted at the // next pass. Known cases that make it necessary: // - The card list is refreshed while the NTP is not shown, for example when changing // the sync settings. // - Dismissing a snippet and having the status card coming to take its place. // - Refresh while being below the fold, for example by tapping the status card. if (aboveTheFold != null) bottomSpacing -= aboveTheFold.itemView.getBottom(); Log.w(TAG, "The RecyclerView items are not attached, can't determine the content " + "height: snap=%s, last=%s. Using full height: %d ", aboveTheFold, lastContentItem, bottomSpacing); } else { int contentHeight = lastContentItem.itemView.getBottom() - aboveTheFold.itemView.getBottom(); bottomSpacing -= contentHeight - mCompensationHeight; } return Math.max(0, bottomSpacing); } public void updatePeekingCardAndHeader() { NewTabPageLayout aboveTheFoldView = findAboveTheFoldView(); if (aboveTheFoldView == null) return; SectionHeaderViewHolder header = findFirstHeader(); if (header == null) return; header.updateDisplay(computeVerticalScrollOffset(), mHasSpaceForPeekingCard); CardViewHolder firstCard = findFirstCard(); if (firstCard != null) updatePeekingCard(firstCard); // Update the space at the bottom, which needs to know about the height of the header. refreshBottomSpacing(); } /** * Updates the peeking state of the provided card. Relies on the dimensions of the header to * be correct, prefer {@link #updatePeekingCardAndHeader} that updates both together. */ public void updatePeekingCard(CardViewHolder peekingCard) { SectionHeaderViewHolder header = findFirstHeader(); if (header == null) { // No header, we must have scrolled quite far. Fallback to a non animated (full bleed) // card. peekingCard.updatePeek(0, /* shouldAnimate */ false); return; } // If we have the card offset field trial enabled, don't peek at all. if (CardsVariationParameters.getFirstCardOffsetDp() != 0) { peekingCard.updatePeek(0, /* shouldAnimate */ false); return; } // Here we consider that if the header is animating (is not completely expanded), the card // should as well. In that case, the space below the header is what we have available. boolean shouldAnimate = header.itemView.getHeight() < mMaxHeaderHeight; peekingCard.updatePeek(getHeight() - header.itemView.getBottom(), shouldAnimate); } public NewTabPageAdapter getNewTabPageAdapter() { return (NewTabPageAdapter) getAdapter(); } public LinearLayoutManager getLinearLayoutManager() { return mLayoutManager; } /** * Returns the approximate adapter position that the user has scrolled to. The purpose of this * value is that it can be stored and later retrieved to restore a scroll position that is * familiar to the user, showing (part of) the same content the user was previously looking at. * This position is valid for that purpose regardless of device orientation changes. Note that * if the underlying data has changed in the meantime, different content would be shown for this * position. */ public int getScrollPosition() { return mLayoutManager.findFirstVisibleItemPosition(); } /** * Finds the view holder for the first header. * @return The {@code ViewHolder} of the header, or null if it is not present. */ private SectionHeaderViewHolder findFirstHeader() { int firstHeaderPosition = getNewTabPageAdapter().getFirstHeaderPosition(); if (firstHeaderPosition == RecyclerView.NO_POSITION) return null; ViewHolder viewHolder = findViewHolderForAdapterPosition(firstHeaderPosition); if (!(viewHolder instanceof SectionHeaderViewHolder)) return null; return (SectionHeaderViewHolder) viewHolder; } /** * Finds the view holder for the first card. * @return The {@code ViewHolder} for the first card, or null if it is not present. */ private CardViewHolder findFirstCard() { int firstCardPosition = getNewTabPageAdapter().getFirstCardPosition(); if (firstCardPosition == RecyclerView.NO_POSITION) return null; ViewHolder viewHolder = findViewHolderForAdapterPosition(firstCardPosition); if (!(viewHolder instanceof CardViewHolder)) return null; return (CardViewHolder) viewHolder; } /** * Finds the view holder for the last content item: the footer. * @return The {@code ViewHolder} of the last content item, or null if it is not present. */ private ViewHolder findLastContentItem() { int lastContentItemPosition = getNewTabPageAdapter().getLastContentItemPosition(); if (lastContentItemPosition == RecyclerView.NO_POSITION) return null; ViewHolder viewHolder = findViewHolderForAdapterPosition(lastContentItemPosition); if (viewHolder instanceof Footer.ViewHolder) return viewHolder; return null; } /** * Finds the view holder for the bottom spacer. * @return The {@code ViewHolder} of the bottom spacer, or null if it is not present. */ private ViewHolder findBottomSpacer() { int bottomSpacerPosition = getNewTabPageAdapter().getBottomSpacerPosition(); if (bottomSpacerPosition == RecyclerView.NO_POSITION) return null; return findViewHolderForAdapterPosition(bottomSpacerPosition); } /** * Finds the above the fold view. * @return The View for above the fold or null, if it is not present. */ public NewTabPageLayout findAboveTheFoldView() { int aboveTheFoldPosition = getNewTabPageAdapter().getAboveTheFoldPosition(); if (aboveTheFoldPosition == RecyclerView.NO_POSITION) return null; ViewHolder viewHolder = findViewHolderForAdapterPosition(aboveTheFoldPosition); if (viewHolder == null) return null; View view = viewHolder.itemView; if (!(view instanceof NewTabPageLayout)) return null; return (NewTabPageLayout) view; } /** Called when an item is in the process of being removed from the view. */ public void onItemDismissStarted(ViewHolder viewHolder) { assert !mCompensationHeightMap.containsKey(viewHolder); int dismissedHeight = viewHolder.itemView.getHeight(); ViewHolder siblingViewHolder = getNewTabPageAdapter().getDismissSibling(viewHolder); if (siblingViewHolder != null) { dismissedHeight += siblingViewHolder.itemView.getHeight(); } mCompensationHeightMap.put(viewHolder, dismissedHeight); mCompensationHeight += dismissedHeight; refreshBottomSpacing(); } /** Called when an item has finished being removed from the view. */ public void onItemDismissFinished(ViewHolder viewHolder) { assert mCompensationHeightMap.containsKey(viewHolder); mCompensationHeight -= mCompensationHeightMap.remove(viewHolder); assert mCompensationHeight >= 0; refreshBottomSpacing(); } /** * If the RecyclerView is currently scrolled to between regionStart and regionEnd, smooth scroll * out of the region. flipPoint is the threshold used to decide which bound of the region to * scroll to. It returns whether the view was scrolled. */ private boolean scrollOutOfRegion(int regionStart, int flipPoint, int regionEnd) { final int currentScroll = computeVerticalScrollOffset(); if (currentScroll < regionStart || currentScroll > regionEnd) return false; if (currentScroll < flipPoint) { smoothScrollBy(0, regionStart - currentScroll); } else { smoothScrollBy(0, regionEnd - currentScroll); } return true; } /** * If the RecyclerView is currently scrolled to between regionStart and regionEnd, smooth scroll * out of the region to the nearest edge. */ private boolean scrollOutOfRegion(int regionStart, int regionEnd) { return scrollOutOfRegion(regionStart, (regionStart + regionEnd) / 2, regionEnd); } /** * Snaps the scroll point of the RecyclerView to prevent the user from scrolling to midway * through a transition and to allow peeking card behaviour. */ public void snapScroll(View fakeBox, int parentScrollY, int parentHeight) { // Snap scroll to prevent resting in the middle of the omnibox transition. final int searchBoxTransitionLength = getResources() .getDimensionPixelSize(R.dimen.ntp_search_box_transition_length); int fakeBoxUpperBound = fakeBox.getTop() + fakeBox.getPaddingTop(); if (scrollOutOfRegion(fakeBoxUpperBound - searchBoxTransitionLength, fakeBoxUpperBound)) { // The snap scrolling regions should never overlap. return; } // Snap scroll to prevent resting in the middle of the peeking card transition // and to allow the peeking card to peek a bit before snapping back. CardViewHolder peekingCardViewHolder = findFirstCard(); if (peekingCardViewHolder != null && isFirstItemVisible()) { if (!mHasSpaceForPeekingCard) return; ViewHolder firstHeaderViewHolder = findFirstHeader(); // It is possible to have a card but no header, for example the sign in promo. // That one does not peek. if (firstHeaderViewHolder == null) return; View peekingCardView = peekingCardViewHolder.itemView; View headerView = firstHeaderViewHolder.itemView; final int peekingHeight = getResources() .getDimensionPixelSize(R.dimen.snippets_padding_and_peeking_card_height); // |A + B - C| gives the offset of the peeking card relative to the Recycler View, // so scrolling to this point would put the peeking card at the top of the // screen. Remove the |headerView| height which gets dynamically increased with // scrolling. // |A + B - C - D| will scroll us so that the peeking card is just off the bottom // of the screen. // Finally, we get |A + B - C - D + E| because the transition starts from the // peeking card's resting point, which is |E| from the bottom of the screen. int start = peekingCardView.getTop() // A. + parentScrollY // B. - headerView.getHeight() // C. - parentHeight // D. + peekingHeight; // E. // The height of the region in which the the peeking card will snap. int snapScrollHeight = peekingHeight + headerView.getHeight(); scrollOutOfRegion(start, start + snapScrollHeight, start + snapScrollHeight); } } @Override public boolean gatherTransparentRegion(Region region) { ViewUtils.gatherTransparentRegionsForOpaqueView(this, region); return true; } /** * Animates the card being swiped to the right as if the user had dismissed it. Any changes to * the animation here should be reflected also in * {@link #updateViewStateForDismiss(float, ViewHolder)} and reset in * {@link CardViewHolder#onBindViewHolder()}. * @param suggestion The item to be dismissed. */ public void dismissItemWithAnimation(SnippetArticle suggestion) { // We need to recompute the position, as it might have changed. final int position = getNewTabPageAdapter().getSuggestionPosition(suggestion); if (position == RecyclerView.NO_POSITION) { // The item does not exist anymore, so ignore. return; } final View itemView = mLayoutManager.findViewByPosition(position); if (itemView == null) { // The view is not visible anymore, skip the animation. getNewTabPageAdapter().dismissItem(position); return; } final ViewHolder viewHolder = getChildViewHolder(itemView); if (!((NewTabPageViewHolder) viewHolder).isDismissable()) { // The item is not dismissable (anymore), so ignore. return; } AnimatorSet animation = new AnimatorSet(); animation.playTogether(ObjectAnimator.ofFloat(itemView, View.ALPHA, 0f), ObjectAnimator.ofFloat(itemView, View.TRANSLATION_X, (float) itemView.getWidth())); animation.setDuration(DISMISS_ANIMATION_TIME_MS); animation.setInterpolator(DISMISS_INTERPOLATOR); animation.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationStart(Animator animation) { NewTabPageRecyclerView.this.onItemDismissStarted(viewHolder); } @Override public void onAnimationEnd(Animator animation) { getNewTabPageAdapter().dismissItem(position); NewTabPageRecyclerView.this.onItemDismissFinished(viewHolder); } }); animation.start(); } /** * Update the view's state as it is being swiped away. Any changes to the animation here should * be reflected also in {@link #dismissItemWithAnimation(SnippetArticle)} and reset in * {@link CardViewHolder#onBindViewHolder()}. * @param dX The amount of horizontal displacement caused by user's action. * @param viewHolder The view holder containing the view to be updated. */ public void updateViewStateForDismiss(float dX, ViewHolder viewHolder) { if (!((NewTabPageViewHolder) viewHolder).isDismissable()) return; viewHolder.itemView.setTranslationX(dX); float input = Math.abs(dX) / viewHolder.itemView.getMeasuredWidth(); float alpha = 1 - DISMISS_INTERPOLATOR.getInterpolation(input); viewHolder.itemView.setAlpha(alpha); } }