android.support.v7.widget.RecyclerView.AdapterDataObserver#org.chromium.chrome.browser.ntp.cards.NewTabPageRecyclerView源码实例Demo

/**
 * Constructs a {@link SnippetArticleViewHolder} item used to display snippets.
 *
 * @param parent The NewTabPageRecyclerView that is going to contain the newly created view.
 * @param manager The NewTabPageManager object used to open an article.
 * @param uiConfig The NTP UI configuration object used to adjust the article UI.
 */
public SnippetArticleViewHolder(NewTabPageRecyclerView parent, NewTabPageManager manager,
        UiConfig uiConfig) {
    super(R.layout.new_tab_page_snippets_card, parent, uiConfig, manager);

    mNewTabPageManager = manager;
    mThumbnailView = (ImageView) itemView.findViewById(R.id.article_thumbnail);
    mHeadlineTextView = (TextView) itemView.findViewById(R.id.article_headline);
    mPublisherTextView = (TextView) itemView.findViewById(R.id.article_publisher);
    mArticleSnippetTextView = (TextView) itemView.findViewById(R.id.article_snippet);
    mPublisherBar = itemView.findViewById(R.id.publisher_bar);
    mOfflineBadge = (ImageView) itemView.findViewById(R.id.offline_icon);

    new ImpressionTracker(itemView, this);

    mUiConfig = uiConfig;
    new DisplayStyleObserverAdapter(itemView, uiConfig, new DisplayStyleObserver() {
        @Override
        public void onDisplayStyleChanged(@UiConfig.DisplayStyle int newDisplayStyle) {
            updateLayout();
        }
    });

    mUseFaviconService = CardsVariationParameters.isFaviconServiceEnabled();
}
 

public SnippetHeaderViewHolder(final View cardView, final NewTabPageRecyclerView recyclerView) {
    super(cardView);
    mMaxSnippetHeaderHeight = cardView.getResources().getDimensionPixelSize(
            R.dimen.snippets_article_header_height);

    mMaxPeekPadding = cardView.getResources().getDimensionPixelSize(
            R.dimen.snippets_padding_and_peeking_card_height);

    mRecyclerView = recyclerView;
}
 

public SectionHeaderViewHolder(final NewTabPageRecyclerView recyclerView, UiConfig config) {
    super(LayoutInflater.from(recyclerView.getContext())
                    .inflate(R.layout.new_tab_page_snippets_header, recyclerView, false));
    mMaxSnippetHeaderHeight = itemView.getResources().getDimensionPixelSize(
            R.dimen.snippets_article_header_height);
    MarginResizer.createWithViewAdapter(itemView, config);
}
 

@VisibleForTesting
public NewTabPageRecyclerView getRecyclerView() {
    return mRecyclerView;
}
 

/**
 * Uses the total vertical space to determine and configure the layout. This can be one of:
 * - If our contents cannot fit on the screen, increase the spacing to push the Most Likely
 *   partially off the screen, suggesting to users they can scroll.
 * - If our contents can fit on the screen, increase the spacing to fill the space (minus space
 *   for the CardsUI Peeking card).
 */
private void calculateVerticalSpacing(int widthMeasureSpec, int heightMeasureSpec) {
    mLogoSpacer.setVisibility(View.GONE);
    mSearchBoxSpacer.setVisibility(View.GONE);

    // Remove the extra spacing before measuring because it might not be needed anymore.
    mTileGridLayout.setExtraVerticalSpacing(0);

    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    boolean hasSpaceForPeekingCard = false;
    int spaceToFill = mParentViewportHeight - mPeekingCardHeight - mTabStripHeight;
    @NTPLayoutResult int layoutResult;

    if (ChromeFeatureList.isEnabled(ChromeFeatureList.NTP_CONDENSED_LAYOUT)) {
        layoutResult = NewTabPageUma.NTP_LAYOUT_CONDENSED;
    } else if (getMeasuredHeight() > spaceToFill) {
        // We need to make sure we have just enough space to show the peeking card.
        layoutResult = NewTabPageUma.NTP_LAYOUT_DOES_NOT_FIT;

        // We don't have enough, we will push the peeking card completely below the fold
        // and let the tile grid get cut to make it clear that the page is scrollable.
        if (mTileGridLayout.getChildCount() > 0) {
            // Add some extra space if needed (the 'bleed' is the amount of the layout that
            // will be cut off by the bottom of the screen).
            int currentBleed = getMeasuredHeight() - mParentViewportHeight - mTabStripHeight;
            int minimumBleed = (int) (mTileGridLayout.getChildAt(0).getMeasuredHeight() * 0.44);
            if (currentBleed < minimumBleed) {
                int extraBleed = minimumBleed - currentBleed;
                mLogoSpacer.getLayoutParams().height = (int) (extraBleed * 0.25);
                mLogoSpacer.setVisibility(View.INVISIBLE);
                mSearchBoxSpacer.getLayoutParams().height = (int) (extraBleed * 0.25);
                mSearchBoxSpacer.setVisibility(View.INVISIBLE);
                mTileGridLayout.setExtraVerticalSpacing((int) (extraBleed * 0.5));
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);

                layoutResult = NewTabPageUma.NTP_LAYOUT_DOES_NOT_FIT_PUSH_MOST_LIKELY;
            }
        }
    } else {
        hasSpaceForPeekingCard = true;
        // We leave more than or just enough space needed for the peeking card. Redistribute
        // any weighted space.

        // There is a field trial experiment to determine the effect of raising the peeking
        // card, allowing the user to see some of it's contents when scrolled to the top. This
        // is achieved by making the NewTabPageLayout smaller.
        // If there is enough space, reduce the space we are going to fill.
        if (mFieldTrialLayoutAdjustment != 0f) {
            if (getMeasuredHeight() < spaceToFill - mFieldTrialLayoutAdjustment) {
                spaceToFill -= mFieldTrialLayoutAdjustment;
                layoutResult = NewTabPageUma.NTP_LAYOUT_FITS_WITH_FIELD_TRIAL;
            } else {
                layoutResult = NewTabPageUma.NTP_LAYOUT_FITS_WITHOUT_FIELD_TRIAL;
            }
        } else {
            layoutResult = NewTabPageUma.NTP_LAYOUT_FITS_NO_FIELD_TRIAL;
        }

        // Call super.onMeasure with mode EXACTLY and the target height to allow the top
        // spacer (which has a weight of 1) to grow and take up the remaining space.
        heightMeasureSpec =
                MeasureSpec.makeMeasureSpec(spaceToFill, MeasureSpec.EXACTLY);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        distributeExtraSpace(mTopSpacer.getMeasuredHeight());
    }

    NewTabPageRecyclerView recyclerView = (NewTabPageRecyclerView) getParent();
    recyclerView.setHasSpaceForPeekingCard(hasSpaceForPeekingCard);

    // The first few runs of this method occur before the tile grid layout has loaded its
    // contents. We want to record what the user sees when the layout has stabilized.
    if (mTileGridLayout.getChildCount() > 0 && !mLayoutResultRecorded) {
        mLayoutResultRecorded = true;
        NewTabPageUma.recordNTPLayoutResult(layoutResult);
    }
}