在Android项目中使用RecyclerView实现一个上拉加载更多功能

在Android项目中使用RecyclerView实现一个上拉加载更多功能？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。

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既然有刷新的时候有两种状态就要定义两个状态

//普通布局的type
static final int TYPE_ITEM = 0;
//脚布局
static final int TYPE_FOOTER = 1;

在特定的时候去显示:

 @Override
  public int getItemViewType(int position) {
    //如果position加1正好等于所有item的总和,说明是最后一个item,将它设置为脚布局
    if (position + 1 == getItemCount()) {
      return TYPE_FOOTER;
    } else {
      return TYPE_ITEM;
    }
  }

然后根据这个type来inflate不同的布局:

 @Override
  public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    if (viewType == TYPE_ITEM) {
      View view = View.inflate(mContext, R.layout.item_recycler, null);
      MyViewHolder holder = new MyViewHolder(view);
      return holder;
    } else if (viewType == TYPE_FOOTER) {
      //脚布局
      View view = View.inflate(mContext, R.layout.recycler_load_more_layout, null);
      FootViewHolder footViewHolder = new FootViewHolder(view);
      return footViewHolder;
    }
    return null;
  }

以上只是控制了Loading布局的出现可隐藏,还要2中状态需要控制就是上面的2个图,一个是正在加载,一个是加载完成状态,这两个状态在adapter里显然是控制不了的,必须要在请求数据的时候才能知道这两种状态,而加载数据又是在activity中执行的,所以我们需要一个用来传递状态的方法:

/**
   * 改变脚布局的状态的方法,在activity根据请求数据的状态来改变这个状态
   *
   * @param state
   */
  public void changeState(int state) {
    this.footer_state = state;
    notifyDataSetChanged();
  }

用来接收状态的变量:

//上拉加载更多
// static final int PULL_LOAD_MORE = 0;
  //正在加载更多
  static final int LOADING_MORE = 1;
  //没有更多
  static final int NO_MORE = 2;
  //脚布局当前的状态,默认为没有更多
  int footer_state = 1;

然后就可以根据这几种状态来控制布局控件的改变了:

 @Override
  public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof MyViewHolder) {
      ((MyViewHolder) holder).mTextView.setText(mList.get(position));
    } else if (holder instanceof FootViewHolder) {
      FootViewHolder footViewHolder = (FootViewHolder) holder;
      if (position == 0) {//如果第一个就是脚布局,,那就让他隐藏
        footViewHolder.mProgressBar.setVisibility(View.GONE);
        footViewHolder.tv_line1.setVisibility(View.GONE);
        footViewHolder.tv_line2.setVisibility(View.GONE);
        footViewHolder.tv_state.setText("");
      }
      switch (footer_state) {//根据状态来让脚布局发生改变
//        case PULL_LOAD_MORE://上拉加载
//          footViewHolder.mProgressBar.setVisibility(View.GONE);
//          footViewHolder.tv_state.setText("上拉加载更多");
//          break;
        case LOADING_MORE:
          footViewHolder.mProgressBar.setVisibility(View.VISIBLE);
          footViewHolder.tv_line1.setVisibility(View.GONE);
          footViewHolder.tv_line2.setVisibility(View.GONE);
          footViewHolder.tv_state.setText("正在加载...");
          break;
        case NO_MORE:
          footViewHolder.mProgressBar.setVisibility(View.GONE);
          footViewHolder.tv_line1.setVisibility(View.VISIBLE);
          footViewHolder.tv_line2.setVisibility(View.VISIBLE);
          footViewHolder.tv_state.setText("我是有底线的");
          footViewHolder.tv_state.setTextColor(Color.parseColor("#ff00ff"));
          break;
      }
    }
  }

不要忘了返回的count也要加1,因为添加了一个脚布局:

 @Override
  public int getItemCount() {
    return mList != null ? mList.size() + 1 : 0;
  }

那么什么时候去传递状态到adapter呢?这里就需要给RecyclerView添加滑动监听了,当他滑动到底部的时候显示加载中的状态:

//给recyclerView添加滑动监听
    mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
      @Override
      public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        /*
        到达底部了,如果不加!isLoading的话到达底部如果还一滑动的话就会一直进入这个方法
        就一直去做请求网络的操作,这样的用户体验肯定不好.添加一个判断,每次滑倒底只进行一次网络请求去请求数据
        当请求完成后,在把isLoading赋值为false,下次滑倒底又能进入这个方法了
         */
        if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
          //到达底部之后如果footView的状态不是正在加载的状态,就将 他切换成正在加载的状态
          if (page < totlePage) {
            Log.e("duanlian", "onScrollStateChanged: " + "进来了");
            isLoading = true;
            mAdapter.changeState(1);
            new Handler().postDelayed(new Runnable() {
              @Override
              public void run() {
                getData();
                page++;
              }
            }, 2000);
          } else {
            mAdapter.changeState(2);

          }
        }
      }

      @Override
      public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        //拿到最后一个出现的item的位置
        lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
      }
    });

重点就这几个,下面给出脚布局:

<?xml version="1.0" encoding="utf-8"?>

Adapter的代码:

package com.duanlian.recyclerviewloadmoredemo;

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

import java.util.List;


public class MyRecyclerAdapter extends RecyclerView.Adapter {
  private Context mContext;
  private List mList;
  //普通布局的type
  static final int TYPE_ITEM = 0;
  //脚布局
  static final int TYPE_FOOTER = 1;
  //  //上拉加载更多
//  static final int PULL_LOAD_MORE = 0;
  //正在加载更多
  static final int LOADING_MORE = 1;
  //没有更多
  static final int NO_MORE = 2;
  //脚布局当前的状态,默认为没有更多
  int footer_state = 1;

  public MyRecyclerAdapter(Context context, List list) {
    mContext = context;
    mList = list;
  }

  @Override
  public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    if (viewType == TYPE_ITEM) {
      View view = View.inflate(mContext, R.layout.item_recycler, null);
      MyViewHolder holder = new MyViewHolder(view);
      return holder;
    } else if (viewType == TYPE_FOOTER) {
      //脚布局
      View view = View.inflate(mContext, R.layout.recycler_load_more_layout, null);
      FootViewHolder footViewHolder = new FootViewHolder(view);
      return footViewHolder;
    }
    return null;
  }

  @Override
  public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof MyViewHolder) {
      ((MyViewHolder) holder).mTextView.setText(mList.get(position));
    } else if (holder instanceof FootViewHolder) {
      FootViewHolder footViewHolder = (FootViewHolder) holder;
      if (position == 0) {//如果第一个就是脚布局,,那就让他隐藏
        footViewHolder.mProgressBar.setVisibility(View.GONE);
        footViewHolder.tv_line1.setVisibility(View.GONE);
        footViewHolder.tv_line2.setVisibility(View.GONE);
        footViewHolder.tv_state.setText("");
      }
      switch (footer_state) {//根据状态来让脚布局发生改变
//        case PULL_LOAD_MORE://上拉加载
//          footViewHolder.mProgressBar.setVisibility(View.GONE);
//          footViewHolder.tv_state.setText("上拉加载更多");
//          break;
        case LOADING_MORE:
          footViewHolder.mProgressBar.setVisibility(View.VISIBLE);
          footViewHolder.tv_line1.setVisibility(View.GONE);
          footViewHolder.tv_line2.setVisibility(View.GONE);
          footViewHolder.tv_state.setText("正在加载...");
          break;
        case NO_MORE:
          footViewHolder.mProgressBar.setVisibility(View.GONE);
          footViewHolder.tv_line1.setVisibility(View.VISIBLE);
          footViewHolder.tv_line2.setVisibility(View.VISIBLE);
          footViewHolder.tv_state.setText("我是有底线的");
          footViewHolder.tv_state.setTextColor(Color.parseColor("#ff00ff"));
          break;
      }
    }
  }


  @Override
  public int getItemViewType(int position) {
    //如果position加1正好等于所有item的总和,说明是最后一个item,将它设置为脚布局
    if (position + 1 == getItemCount()) {
      return TYPE_FOOTER;
    } else {
      return TYPE_ITEM;
    }
  }

  @Override
  public int getItemCount() {
    return mList != null ? mList.size() + 1 : 0;
  }

  /**
   * 正常布局的ViewHolder
   */
  class MyViewHolder extends RecyclerView.ViewHolder {
    TextView mTextView;

    public MyViewHolder(View itemView) {
      super(itemView);
      mTextView = (TextView) itemView.findViewById(R.id.item_textView);
    }
  }

  /**
   * 脚布局的ViewHolder
   */
  public static class FootViewHolder extends RecyclerView.ViewHolder {
    private ProgressBar mProgressBar;
    private TextView tv_state;
    private TextView tv_line1;
    private TextView tv_line2;


    public FootViewHolder(View itemView) {
      super(itemView);
      mProgressBar = (ProgressBar) itemView.findViewById(R.id.progressbar);
      tv_state = (TextView) itemView.findViewById(R.id.foot_view_item_tv);
      tv_line1 = (TextView) itemView.findViewById(R.id.tv_line1);
      tv_line2 = (TextView) itemView.findViewById(R.id.tv_line2);

    }
  }

  /**
   * 改变脚布局的状态的方法,在activity根据请求数据的状态来改变这个状态
   *
   * @param state
   */
  public void changeState(int state) {
    this.footer_state = state;
    notifyDataSetChanged();
  }

}

activity中的代码:

package com.duanlian.recyclerviewloadmoredemo;

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

  private RecyclerView mRecycler;
  private List mList;
  private List list;
  private MyRecyclerAdapter mAdapter;
  LinearLayoutManager linearLayoutManager;
  int lastVisibleItem;
  int page = 0;
  boolean isLoading = false;//用来控制进入getdata()的次数
  int totlePage = 5;//模拟请求的一共的页数

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initView();
    getData();
  }

  private void initView() {
    mRecycler = (RecyclerView) findViewById(R.id.recycler);
    linearLayoutManager = new LinearLayoutManager(this);
    mRecycler.setLayoutManager(linearLayoutManager);
    mList = new ArrayList<>();
    mAdapter = new MyRecyclerAdapter(this, mList);
    mRecycler.setAdapter(mAdapter);
    //给recyclerView添加滑动监听
    mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
      @Override
      public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        /*
        到达底部了,如果不加!isLoading的话到达底部如果还一滑动的话就会一直进入这个方法
        就一直去做请求网络的操作,这样的用户体验肯定不好.添加一个判断,每次滑倒底只进行一次网络请求去请求数据
        当请求完成后,在把isLoading赋值为false,下次滑倒底又能进入这个方法了
         */
        if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
          //到达底部之后如果footView的状态不是正在加载的状态,就将 他切换成正在加载的状态
          if (page < totlePage) {
            Log.e("duanlian", "onScrollStateChanged: " + "进来了");
            isLoading = true;
            mAdapter.changeState(1);
            new Handler().postDelayed(new Runnable() {
              @Override
              public void run() {
                getData();
                page++;
              }
            }, 2000);
          } else {
            mAdapter.changeState(2);

          }
        }
      }

      @Override
      public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        //拿到最后一个出现的item的位置
        lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
      }
    });

  }

  /**
   * 模拟请求数据
   */
  private void getData() {
    list = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
      list.add("第" + i + "条");
    }
    mList.addAll(list);
    isLoading = false;
    mAdapter = new MyRecyclerAdapter(this, mList);
    mRecycler.setAdapter(mAdapter);
  }
}

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