RecyclerViewLoadMoreHelper

RecyclerViewLoadMoreHelper

import android.support.annotation.NonNull;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;

/**
 * 封装加载更多通用辅助类
 *
 * @author puke
 * @version 2020-07-24
 */
public class RecyclerViewLoadMoreHelper {

    private static final int DEFAULT_LOAD_MORE_WHEN_SHOW_LAST_COUNT = 10;

    private final RecyclerView recyclerView;
    private final int loadMoreWhenShowLastCount;
    private OnLoadMoreListener loadMoreListener;
    private boolean locked;
    private boolean enabled = true;

    public interface OnLoadMoreListener {
        void onLoadMore();
    }

    public RecyclerViewLoadMoreHelper(RecyclerView recyclerView) {
        this(recyclerView, DEFAULT_LOAD_MORE_WHEN_SHOW_LAST_COUNT);
    }

    public RecyclerViewLoadMoreHelper(RecyclerView recyclerView, int loadMoreWhenShowLastCount) {
        this.recyclerView = recyclerView;
        this.loadMoreWhenShowLastCount = loadMoreWhenShowLastCount;
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                doCheck();
            }
        });
    }

    /**
     * 注册加载更多回调
     */
    public void setOnLoadMoreListener(OnLoadMoreListener loadMoreListener) {
        this.loadMoreListener = loadMoreListener;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    /**
     * 锁定加载更多, 调用之后, 不再回调加载更多事件
     */
    public void lock() {
        locked = true;
    }

    /**
     * 解锁加载更多, 调用之后, 继续回调加载更多事件
     */
    public void unlock() {
        locked = false;
    }

    public void doCheck() {
        doCheck(false);
    }

    /**
     * 手动触发加载更多检测逻辑
     *
     * @param force 是否强制检测 true: 忽略lock逻辑
     */
    public void doCheck(boolean force) {
        if (!enabled) {
            return;
        }
        if (locked && !force) {
            return;
        }
        RecyclerView.Adapter adapter = recyclerView.getAdapter();
        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();

        if (adapter == null) {
            return;
        }

        if (layoutManager instanceof LinearLayoutManager) {
            int lastVisibleItemPosition =
                    ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
            if (lastVisibleItemPosition >= adapter.getItemCount() - loadMoreWhenShowLastCount) {
                if (loadMoreListener != null) {
                    loadMoreListener.onLoadMore();
                }
            }
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            StaggeredGridLayoutManager gridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
            int[] lastVisibleItemPositions = gridLayoutManager.findLastVisibleItemPositions(null);
            for (int lastVisibleItemPosition : lastVisibleItemPositions) {
                if (lastVisibleItemPosition >= adapter.getItemCount() - loadMoreWhenShowLastCount) {
                    if (loadMoreListener != null) {
                        loadMoreListener.onLoadMore();
                    }
                    break;
                }
            }
        }
    }
}