JazzyRecyclerViewScrollListener.java

package com.twotoasters.jazzylistview.recyclerview;

import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.OnScrollListener;

import com.twotoasters.jazzylistview.JazzyEffect;
import com.twotoasters.jazzylistview.JazzyHelper;

public class JazzyRecyclerViewScrollListener extends OnScrollListener {

    private final JazzyHelper mHelper;
    private OnScrollListener mAdditionalOnScrollListener;

    public JazzyRecyclerViewScrollListener() {
        mHelper = new JazzyHelper();
    }

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        int firstVisibleItem = recyclerView.getChildPosition(recyclerView.getChildAt(0));
        int visibleItemCount = recyclerView.getChildCount();
        int totalItemCount = recyclerView.getAdapter().getItemCount();

        mHelper.onScrolled(recyclerView, firstVisibleItem, visibleItemCount, totalItemCount);

        notifyAdditionalOnScrolledListener(recyclerView, dx, dy);
    }

    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        switch (newState) {
            case RecyclerView.SCROLL_STATE_SETTLING: // fall through
            case RecyclerView.SCROLL_STATE_DRAGGING:
                mHelper.setScrolling(true);
                break;
            case RecyclerView.SCROLL_STATE_IDLE:
                mHelper.setScrolling(false);
                break;
            default:
                break;
        }
        notifyAdditionalOnScrollStateChangedListener(recyclerView, newState);
    }

    /**
     * Sets the desired transition effect.
     *
     * @param transitionEffect Numeric constant representing a bundled transition effect.
     */
    public void setTransitionEffect(int transitionEffect) {
        mHelper.setTransitionEffect(transitionEffect);
    }

    /**
     * Sets the desired transition effect.
     *
     * @param transitionEffect The non-bundled transition provided by the client.
     */
    public void setTransitionEffect(JazzyEffect transitionEffect) {
        mHelper.setTransitionEffect(transitionEffect);
    }

    /**
     * Sets whether new items or all items should be animated when they become visible.
     *
     * @param onlyAnimateNew True if only new items should be animated; false otherwise.
     */
    public void setShouldOnlyAnimateNewItems(boolean onlyAnimateNew) {
        mHelper.setShouldOnlyAnimateNewItems(onlyAnimateNew);
    }

    /**
     * Stop animations after the list has reached a certain velocity. When the list slows down
     * it will start animating again. This gives a performance boost as well as preventing
     * the list from animating under the users finger if they suddenly stop it.
     *
     * @param itemsPerSecond, set to JazzyHelper.MAX_VELOCITY_OFF to turn off max velocity.
     *        While 13 is a good default, it is dependent on the size of your items.
     */
    public void setMaxAnimationVelocity(int itemsPerSecond) {
        mHelper.setMaxAnimationVelocity(itemsPerSecond);
    }
    
    public void setOnScrollListener(OnScrollListener l) {
        // hijack the scroll listener setter and have this list also notify the additional listener
        mAdditionalOnScrollListener = l;
    }

    /**
     * Notifies the OnScrollListener of an onScroll event, since JazzyListView is the primary listener for onScroll events.
     */
    private void notifyAdditionalOnScrolledListener(RecyclerView recyclerView, int dx, int dy) {
        if (mAdditionalOnScrollListener != null) {
            mAdditionalOnScrollListener.onScrolled(recyclerView, dx, dy);
        }
    }

    /**
     * Notifies the OnScrollListener of an onScrollStateChanged event, since JazzyListView is the primary listener for onScrollStateChanged events.
     */
    private void notifyAdditionalOnScrollStateChangedListener(RecyclerView recyclerView, int newState) {
        if (mAdditionalOnScrollListener != null) {
            mAdditionalOnScrollListener.onScrollStateChanged(recyclerView, newState);
        }
    }
}