LoadMoreRecyclerView.java

package com.gzsll.hupu.widget;

import android.content.Context;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.gzsll.hupu.R;

/**
 * Created by sll on 2016/4/7.
 */
public class LoadMoreRecyclerView extends RecyclerView {
    /**
     * item 类型
     */
    public final static int TYPE_NORMAL = 0;
    public final static int TYPE_FOOTER = 1;
    public final static int TYPE_LIST = 2;
    public final static int TYPE_STAGGER = 3;

    private boolean mIsFooterEnable = false;//是否允许加载更多

    private AutoLoadAdapter mAutoLoadAdapter;

    private boolean mIsLoadingMore;
    private int mLoadMorePosition;
    private LoadMoreListener mListener;

    public LoadMoreRecyclerView(Context context) {
        this(context, null);
    }

    public LoadMoreRecyclerView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LoadMoreRecyclerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        addOnScrollListener(new OnScrollListener() {

            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                if (null != mListener && mIsFooterEnable && !mIsLoadingMore && dy > 0) {
                    int lastVisiblePosition = getLastVisiblePosition();
                    if (lastVisiblePosition + 1 == mAutoLoadAdapter.getItemCount()) {
                        setLoadingMore(true);
                        mLoadMorePosition = lastVisiblePosition;
                        mListener.onLoadMore();
                    }
                }
            }
        });
    }

    /**
     * 设置加载更多的监听
     */
    public void setLoadMoreListener(LoadMoreListener listener) {
        mListener = listener;
    }

    /**
     * 设置正在加载更多
     */
    public void setLoadingMore(boolean loadingMore) {
        this.mIsLoadingMore = loadingMore;
    }

    /**
     * 加载更多监听
     */
    public interface LoadMoreListener {
        /**
         * 加载更多
         */
        void onLoadMore();
    }

    /**
     *
     */
    public class AutoLoadAdapter extends Adapter<ViewHolder> {

        /**
         * 数据adapter
         */
        private Adapter mInternalAdapter;

        public AutoLoadAdapter(Adapter adapter) {
            mInternalAdapter = adapter;
        }

        @Override
        public int getItemViewType(int position) {
            int footerPosition = getItemCount() - 1;

            if (footerPosition == position && mIsFooterEnable) {
                return TYPE_FOOTER;
            }
            if (getLayoutManager() instanceof LinearLayoutManager) {
                return TYPE_LIST;
            } else if (getLayoutManager() instanceof StaggeredGridLayoutManager) {
                return TYPE_STAGGER;
            } else {
                return TYPE_NORMAL;
            }
        }

        @Override
        public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            if (viewType == TYPE_FOOTER) {
                return new FooterViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.layout_foot_loading, parent, false));
            } else { // type normal
                return mInternalAdapter.onCreateViewHolder(parent, viewType);
            }
        }

        public class FooterViewHolder extends ViewHolder {

            public FooterViewHolder(View itemView) {
                super(itemView);
            }
        }

        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            int type = getItemViewType(position);
            if (type != TYPE_FOOTER) {
                mInternalAdapter.onBindViewHolder(holder, position);
            }
        }

        @Override
        public int getItemCount() {
            int count = mInternalAdapter.getItemCount();
            if (mIsFooterEnable) count++;

            return count;
        }
    }

    @Override
    public void setAdapter(Adapter adapter) {
        if (adapter != null) {
            mAutoLoadAdapter = new AutoLoadAdapter(adapter);
        }
        super.swapAdapter(mAutoLoadAdapter, true);
    }

    /**
     * 获取最后一条展示的位置
     */
    private int getLastVisiblePosition() {
        int position;
        if (getLayoutManager() instanceof LinearLayoutManager) {
            position = ((LinearLayoutManager) getLayoutManager()).findLastVisibleItemPosition();
        } else if (getLayoutManager() instanceof GridLayoutManager) {
            position = ((GridLayoutManager) getLayoutManager()).findLastVisibleItemPosition();
        } else if (getLayoutManager() instanceof StaggeredGridLayoutManager) {
            StaggeredGridLayoutManager layoutManager = (StaggeredGridLayoutManager) getLayoutManager();
            int[] lastPositions =
                    layoutManager.findLastVisibleItemPositions(new int[layoutManager.getSpanCount()]);
            position = getMaxPosition(lastPositions);
        } else {
            position = getLayoutManager().getItemCount() - 1;
        }
        return position;
    }

    /**
     * 获得最大的位置
     */
    private int getMaxPosition(int[] positions) {
        int size = positions.length;
        int maxPosition = Integer.MIN_VALUE;
        for (int i = 0; i < size; i++) {
            maxPosition = Math.max(maxPosition, positions[i]);
        }
        return maxPosition;
    }

    /**
     * 设置是否支持自动加载更多
     */
    public void setLoadMoreEnable(boolean autoLoadMore) {
        mIsFooterEnable = autoLoadMore;
    }

    public void onLoadCompleted(boolean hasMore) {
        setLoadMoreEnable(hasMore);
        if (mIsLoadingMore) {
            getAdapter().notifyItemRemoved(mLoadMorePosition);
        }
        mIsLoadingMore = false;
    }
}