RecyclerViewHelper.java

/*
 * Created by LuaView.
 * Copyright (c) 2017, Alibaba Group. All rights reserved.
 *
 * This source code is licensed under the MIT.
 * For the full copyright and license information,please view the LICENSE file in the root directory of this source tree.
 */

package com.taobao.luaview.view.recyclerview;

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

/**
 * RecyclerView 相关操作
 *
 * @author song
 * @date 16/1/13
 */
public class RecyclerViewHelper {

    /**
     * get first visible position of recycler view
     *
     * @param rv
     * @return
     */
    public static int getFirstVisiblePosition(RecyclerView rv) {
        if (rv != null) {
            final RecyclerView.LayoutManager layoutManager = rv.getLayoutManager();
            if (layoutManager instanceof LinearLayoutManager) {
                return ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();
            }
        }
        return 0;
    }

    /**
     * get last visible position of recycler view
     *
     * @param rv
     * @return
     */
    public static int getLastVisiblePosition(RecyclerView rv) {
        if (rv != null) {
            final RecyclerView.LayoutManager layoutManager = rv.getLayoutManager();
            if (layoutManager instanceof LinearLayoutManager) {
                return ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
            }
        }
        return 0;
    }

    /**
     * get visible item count of recycler view;
     *
     * @param rv
     * @return
     */
    public static int getVisibleItemCount(RecyclerView rv) {
        final int firstVisiblePos = getFirstVisiblePosition(rv);
        final int lastVisiblePos = getLastVisiblePosition(rv);
        return Math.max(0, lastVisiblePos - firstVisiblePos);
    }
}