RecyclerViewUtils.java

package zone.com.zrefreshlayout.utils;

import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * [2017] by Zone
 */

public class RecyclerViewUtils {
    /**
     * 判断最后一个条目是否完全可见
     *
     * @param recyclerView
     * @return
     */
    public  static boolean isLastItemVisible(RecyclerView recyclerView) {
        final RecyclerView.Adapter<?> adapter = recyclerView.getAdapter();
        // 如果未设置Adapter或者Adapter没有数据可以上拉刷新
        if (null == adapter || adapter.getItemCount() == 0) {
            return true;
        }
        // 最后一个条目View完全展示,可以刷新
        int lastVisiblePosition = getLastVisiblePosition(recyclerView);
        if (lastVisiblePosition >= recyclerView.getAdapter().getItemCount() - 1) {
            return recyclerView.getChildAt(recyclerView.getChildCount() - 1).getBottom()
                    <= recyclerView.getBottom();
        }
        return false;
    }
    /**
     * 获取最后一个可见子View的位置下标
     *
     * @param recyclerView
     * @return
     */
    public static int getLastVisiblePosition(RecyclerView recyclerView) {
        View lastVisibleChild = recyclerView.getChildAt(recyclerView.getChildCount() - 1);
        return lastVisibleChild != null ? recyclerView.getChildAdapterPosition(lastVisibleChild) : -1;
    }

    /**
     * 判断第一个条目是否完全可见
     *
     * @param recyclerView
     * @return
     */
    public static boolean isFirstItemVisible(RecyclerView recyclerView) {
        final RecyclerView.Adapter<?> adapter = recyclerView.getAdapter();
        // 如果未设置Adapter或者Adapter没有数据可以下拉刷新
        if (null == adapter || adapter.getItemCount() == 0) {
            return true;
        }
        // 第一个条目完全展示,可以刷新
        if (getFirstVisiblePosition(recyclerView) == 0) {
            return recyclerView.getChildAt(0).getTop() >= recyclerView.getTop();
        }
        return false;
    }

    /**
     * 获取第一个可见子View的位置下标
     *
     * @param recyclerView
     * @return
     */
    public static int getFirstVisiblePosition(RecyclerView recyclerView) {
        View firstVisibleChild = recyclerView.getChildAt(0);
        return firstVisibleChild != null ?
                recyclerView.getChildAdapterPosition(firstVisibleChild) : -1;
    }

}