封装RecyclerViewAdapter实现RecyclerView下拉刷新上拉加载更多

实现

关于下拉刷新使用的是github上的项目Ultra Pull To Refresh项目。
gradle依赖如下：

  compile 'in.srain.cube:ultra-ptr:1.0.11'

重点是上拉加载更多的实现，由于RecyclerView并不支持添加HeardView与FooterView,因此我们只能自
己实现。
首先定义一些局部变量

    public static final int STATE_LOAD = 0;
    public static final int STATE_LOADING = 1;
    public static final int STATE_LOADCOMPLE = 2;
    public static final int STATE_NODATA = 3;
    private int mState = STATE_LOAD;
    private ProgressBar pb;
    private TextView tv;
    private View footView;
    public static final int TYPE_FOOT = Integer.MAX_VALUE;

记得在原有Item数量上+1

  @Override
    public int getItemCount() {
        return super.getItemCount() + 1;
    }

通过重写RecyclerView.Adapter的getItemViewType在列表最后返回FOOTER_TYPE。

 @Override
    public int getItemViewType(int position) {
        if(position==getItemCount()-1){
            return TYPE_FOOT;
        }else {
            return  0;
        }
    }

在方法中onCreateViewHolder方法中通过viewType加载指定的布局。

 @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_FOOT) {
            footView = mInflater.inflate(R.layout.layout_footer_more, parent, false);
            tv = (TextView) footView.findViewById(R.id.tv_info);
            pb = (ProgressBar) footView.findViewById(R.id.pb);
            return new FooterHolder(footView);
        } else {
            return super.onCreateViewHolder(parent, viewType);
        }
    }

根据不同的状态设置显示样式

 private String getTextByState() {
        String result = "上拉加载更多";
        pb.setVisibility(View.INVISIBLE);
        footView.setVisibility(View.VISIBLE);
        switch (mState) {
            case STATE_LOAD:
                footView.setVisibility(View.GONE);
                break;
            case STATE_LOADCOMPLE:
                result = "加载完成";
                break;
            case STATE_LOADING:
                result = "正在加载更多....";
                pb.setVisibility(View.VISIBLE);
                break;
            case STATE_NODATA:
                result = "没有更多了";
                break;
        }
        return result;
    }

由于需要一些扩展因此将上一次封装的Adapter做了一些调整。

package trs.com.myapp.adapter;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.util.List;

import trs.com.myapp.R;

/** * Created by zhuguohui on 2016/3/23. */
public class TRSRecyclerAdapter<T, H extends RecyclerView.ViewHolder> extends RecyclerView.Adapter {
    List<T> data;
    Context context;
    protected final LayoutInflater mInflater;
    protected int layoutId;

    public TRSRecyclerAdapter(List<T> data, Context context, int layoutId) {
        this.data = data;
        this.layoutId = layoutId;
        this.context = context;
        mInflater = LayoutInflater.from(context);
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(layoutId, parent, false);
        return getInstanceOfH(view);
    }

    H getInstanceOfH(View view) {
        ParameterizedType superClass = (ParameterizedType) getClass().getGenericSuperclass();
        Class<H> type = (Class<H>) superClass.getActualTypeArguments()[1];
        try {
            Constructor<H> constructor = type.getConstructor(View.class);
            return constructor.newInstance(view);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }


    @Override
    public final void onBindViewHolder(RecyclerView.ViewHolder h, int position) {
        T t = data.get(position);
        bindData(t, h);
    }

    private void setDataToHolder(T t, RecyclerView.ViewHolder h) {
        Field[] fields = h.getClass().getDeclaredFields();
        Object o ;
        for (Field f : fields) {
            f.setAccessible(true);
            o = null;
            try {
                o = f.get(h);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            if (o instanceof TextView) {
                TextView tv = (TextView) o;
                Object value = getValueFromFiled(t, f.getName());
                if (value instanceof CharSequence) {
                    tv.setText((CharSequence) value);
                }
            } else if (o instanceof ImageView) {
                ImageView iv = (ImageView) o;
                Object value = getValueFromFiled(t, f.getName());
                if (value instanceof String) {
                    String url = (String) value;
                    Glide.with(context).load(url).placeholder(R.drawable.default_pic).into(iv);
                }
            }


        }
    }

    public Object getValueFromFiled(T t, String name) {
        try {
            Field hf = t.getClass().getDeclaredField(name);
            hf.setAccessible(true);
            return hf.get(t);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public void bindData(T t, RecyclerView.ViewHolder h) {
        setDataToHolder(t, h);
    }

    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }

}

这是具有加载更多功能的Adapter继承自TRSRecyclerAdapter：

package trs.com.myapp.adapter;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.util.List;

import trs.com.myapp.R;
import trs.com.myapp.holder.TRSViewHolder;

/** * Created by yuelin on 2016/3/28. */
public class TRSMoreAdapter<T, H extends RecyclerView.ViewHolder> extends TRSRecyclerAdapter<T, H> {


    public static final int STATE_LOAD = 0;
    public static final int STATE_LOADING = 1;
    public static final int STATE_LOADCOMPLE = 2;
    public static final int STATE_NODATA = 3;
    private int mState = STATE_LOAD;

    private ProgressBar pb;
    private TextView tv;
    private View footView;
    public static final int TYPE_FOOT = Integer.MAX_VALUE;

    public TRSMoreAdapter(List<T> data, Context context, int layoutId) {
        super(data, context, layoutId);
    }

    @Override
    public int getItemCount() {
        return super.getItemCount() + 1;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position, List payloads) {
        if (holder instanceof FooterHolder) {
            tv.setText(getTextByState());
        } else {
            super.onBindViewHolder(holder, position, payloads);
        }
    }

    private String getTextByState() {
        String result = "上拉加载更多";
        pb.setVisibility(View.INVISIBLE);
        footView.setVisibility(View.VISIBLE);
        switch (mState) {
            case STATE_LOAD:
                footView.setVisibility(View.GONE);
                break;
            case STATE_LOADCOMPLE:
                result = "加载完成";
                break;
            case STATE_LOADING:
                result = "正在加载更多....";
                pb.setVisibility(View.VISIBLE);
                break;
            case STATE_NODATA:
                result = "没有更多了";
                break;
        }
        return result;
    }

    public void setState(int state) {
        if (state != STATE_LOAD && state != STATE_LOADCOMPLE && state != STATE_LOADING && state != STATE_NODATA) {
            throw new RuntimeException("状态有误！");
        }
        mState = state;
        notifyDataSetChanged();
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_FOOT) {
            footView = mInflater.inflate(R.layout.layout_footer_more, parent, false);
            tv = (TextView) footView.findViewById(R.id.tv_info);
            pb = (ProgressBar) footView.findViewById(R.id.pb);
            return new FooterHolder(footView);
        } else {
            return super.onCreateViewHolder(parent, viewType);
        }
    }


    public static class FooterHolder extends TRSViewHolder {
        public TextView title;
        public TextView time;
        public ImageView image;

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

    @Override
    public int getItemViewType(int position) {
        if(position==getItemCount()-1){
            return TYPE_FOOT;
        }else {
            return  0;
        }
    }

}

而关于Adapter状态的改变，需要通过给RecyclerView添加滚动监听器实现。为了方便起见，我将这些添加监听器，设置Adapter状态统统封装在一个LoadMoreRecyclerView中。

package trs.com.myapp.view;

import android.content.Context;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;

import trs.com.myapp.adapter.RefreshAdapter;
import trs.com.myapp.adapter.TRSMoreAdapter;

/** * Created by yuelin on 2016/3/25. */
public class LoadMoreRecyclerView extends RecyclerView {
    private TRSMoreAdapter refreshAdapter;


    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);
        setOnScrollListener(null);
    }


    @Override
    public void setOnScrollListener(OnScrollListener listener) {
        LoadMoreListener loadMoreListener = new LoadMoreListener(listener);
        super.setOnScrollListener(loadMoreListener);
    }

    public interface OnLoadMoreListener {
        void OnLoad();
    }

    OnLoadMoreListener mOnloadmoreLister = null;

    public void SetOnLoadMoreLister(OnLoadMoreListener listener) {
        mOnloadmoreLister = listener;
    }

    private class LoadMoreListener extends OnScrollListener {
        private OnScrollListener listener;
        private int lastVisibleItem;

        public LoadMoreListener(OnScrollListener listener) {
            this.listener = listener;
        }

        @Override
        public void onScrollStateChanged(RecyclerView view, int newState) {
            if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == getAdapter().getItemCount()) {
                if (mOnloadmoreLister != null && haveData) {
                    refreshAdapter.setState(RefreshAdapter.STATE_LOADING);
                    mOnloadmoreLister.OnLoad();
                }
            }

            if (listener != null) {
                listener.onScrollStateChanged(view, newState);
            }
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        //注意：因为findLastVisibleItemPosition方法目前没有在LayoutManger中声明为抽象方法，因此不同直接通过LayoutManager调用。
            if (getLayoutManager() instanceof LinearLayoutManager) {
                LinearLayoutManager lm = (LinearLayoutManager) getLayoutManager();
                lastVisibleItem = lm.findLastVisibleItemPosition();
            } else if (getLayoutManager() instanceof GridLayoutManager) {
                GridLayoutManager gm = (GridLayoutManager) getLayoutManager();
                lastVisibleItem = gm.findLastVisibleItemPosition();
            }

            if (listener != null) {
                listener.onScrolled(recyclerView, dx, dy);
            }
        }
    }


    @Override
    public void setAdapter(Adapter adapter) {
        if(!(adapter instanceof TRSMoreAdapter)){
            throw new IllegalArgumentException("请使用TRSMoreAdapter");
        }
        refreshAdapter = (TRSMoreAdapter) adapter;
        super.setAdapter(refreshAdapter);
    }

    private boolean haveData = true;

    public void loadComplete(final boolean haveData) {
        this.haveData = haveData;
        if (!haveData) {
            refreshAdapter.setState(RefreshAdapter.STATE_NODATA);
        } else {
            refreshAdapter.setState(RefreshAdapter.STATE_LOAD);
        }

    }

}

使用

1.自定义adpater继承自TRSMoreAdapter

package trs.com.myapp.adapter;

import android.content.Context;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

import trs.com.myapp.R;
import trs.com.myapp.bean.NewsItem;
import trs.com.myapp.holder.TRSViewHolder;

/** * Created by zhuguohui on 2016/3/23. */
public class NewsAdapter1 extends TRSMoreAdapter<NewsItem,NewsAdapter1.NewsViewHolder> {


    public NewsAdapter1(List<NewsItem> data, Context context) {
        super(data, context, R.layout.item_news_layout);
    }

    public static class NewsViewHolder extends TRSViewHolder{
        public TextView title;
        public TextView time;
        public ImageView image;
        public NewsViewHolder(View itemView) {
            super(itemView);
        }
    }
}

2.使用
LoadMoreRecyclerView 进行布局

<?xml version="1.0" encoding="utf-8"?>
<in.srain.cube.views.ptr.PtrFrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ptr_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
android:gravity="center"
android:orientation="vertical">
<trs.com.myapp.view.LoadMoreRecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff" />

</in.srain.cube.views.ptr.PtrFrameLayout>

3.设置Adapter与加载更多监听器

//注意adpater必须是基础自TRSMoreAdapter
 recyclerView.setAdapter(adapter);
   recyclerView.SetOnLoadMoreLister(new LoadMoreRecyclerView.OnLoadMoreListener() {
            @Override
            public void OnLoad() {
                pageIndex++;
                loadData(pageIndex);
            }
        });

4.完成时调用：

 if (recyclerView != null) {
            recyclerView.loadComplete(!error&&haseMore);
      }

效果