在Android項目中使用RecyclerView實現一個上拉加載更多功能

發布時間：2020-11-24 15:47:29 來源：億速云閱讀：140 作者：Leah 欄目：移動開發

在Android項目中使用RecyclerView實現一個上拉加載更多功能？很多新手對此不是很清楚，為了幫助大家解決這個難題，下面小編將為大家詳細講解，有這方面需求的人可以來學習下，希望你能有所收獲。

既然有刷新的時候有兩種狀態就要定義兩個狀態

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

在特定的時候去顯示:

 @Override
  public int getItemViewType(int position) {
    //如果position加1正好等于所有item的總和,說明是最后一個item,將它設置為腳布局
    if (position + 1 == getItemCount()) {
      return TYPE_FOOTER;
    } else {
      return TYPE_ITEM;
    }
  }

然后根據這個type來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) {
      //腳布局
      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布局的出現可隱藏,還要2中狀態需要控制就是上面的2個圖,一個是正在加載,一個是加載完成狀態,這兩個狀態在adapter里顯然是控制不了的,必須要在請求數據的時候才能知道這兩種狀態,而加載數據又是在activity中執行的,所以我們需要一個用來傳遞狀態的方法:

/**
   * 改變腳布局的狀態的方法,在activity根據請求數據的狀態來改變這個狀態
   *
   * @param state
   */
  public void changeState(int state) {
    this.footer_state = state;
    notifyDataSetChanged();
  }

用來接收狀態的變量:

//上拉加載更多
// static final int PULL_LOAD_MORE = 0;
  //正在加載更多
  static final int LOADING_MORE = 1;
  //沒有更多
  static final int NO_MORE = 2;
  //腳布局當前的狀態,默認為沒有更多
  int footer_state = 1;

然后就可以根據這幾種狀態來控制布局控件的改變了:

 @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) {//如果第一個就是腳布局,,那就讓他隱藏
        footViewHolder.mProgressBar.setVisibility(View.GONE);
        footViewHolder.tv_line1.setVisibility(View.GONE);
        footViewHolder.tv_line2.setVisibility(View.GONE);
        footViewHolder.tv_state.setText("");
      }
      switch (footer_state) {//根據狀態來讓腳布局發生改變
//        case PULL_LOAD_MORE://上拉加載
//          footViewHolder.mProgressBar.setVisibility(View.GONE);
//          footViewHolder.tv_state.setText("上拉加載更多");
//          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("正在加載...");
          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("我是有底線的");
          footViewHolder.tv_state.setTextColor(Color.parseColor("#ff00ff"));
          break;
      }
    }
  }

不要忘了返回的count也要加1,因為添加了一個腳布局:

 @Override
  public int getItemCount() {
    return mList != null &#63; mList.size() + 1 : 0;
  }

那么什么時候去傳遞狀態到adapter呢?這里就需要給RecyclerView添加滑動監聽了,當他滑動到底部的時候顯示加載中的狀態:

//給recyclerView添加滑動監聽
    mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
      @Override
      public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        /*
        到達底部了,如果不加!isLoading的話到達底部如果還一滑動的話就會一直進入這個方法
        就一直去做請求網絡的操作,這樣的用戶體驗肯定不好.添加一個判斷,每次滑倒底只進行一次網絡請求去請求數據
        當請求完成后,在把isLoading賦值為false,下次滑倒底又能進入這個方法了
         */
        if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
          //到達底部之后如果footView的狀態不是正在加載的狀態,就將 他切換成正在加載的狀態
          if (page < totlePage) {
            Log.e("duanlian", "onScrollStateChanged: " + "進來了");
            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);
        //拿到最后一個出現的item的位置
        lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
      }
    });

重點就這幾個,下面給出腳布局:

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/ll_below"
        android:layout_width="match_parent"
        android:layout_height="45dp"
  >

  <LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="45dp"
    android:gravity="center"
    android:orientation="horizontal">

    <TextView
      android:id="@+id/tv_line1"
      android:layout_width="60dp"
      android:layout_height="1dp"
      android:layout_marginRight="10dp"
      android:background="#ff00ff"
      android:visibility="gone"/>

    <ProgressBar
      android:id="@+id/progressbar"
      android:layout_width="25dp"
      android:layout_height="25dp"
      android:visibility="visible"/>

    <TextView
      android:id="@+id/foot_view_item_tv"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_marginLeft="4dp"
      android:text="上拉加載更多"/>

    <TextView
      android:id="@+id/tv_line2"
      android:layout_width="60dp"
      android:layout_height="1dp"
      android:layout_marginLeft="10dp"
      android:background="#ff00ff"
      android:visibility="gone"/>
  </LinearLayout>
</RelativeLayout>

Adapter的代碼:

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<RecyclerView.ViewHolder> {
  private Context mContext;
  private List<String> mList;
  //普通布局的type
  static final int TYPE_ITEM = 0;
  //腳布局
  static final int TYPE_FOOTER = 1;
  //  //上拉加載更多
//  static final int PULL_LOAD_MORE = 0;
  //正在加載更多
  static final int LOADING_MORE = 1;
  //沒有更多
  static final int NO_MORE = 2;
  //腳布局當前的狀態,默認為沒有更多
  int footer_state = 1;

  public MyRecyclerAdapter(Context context, List<String> 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) {
      //腳布局
      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) {//如果第一個就是腳布局,,那就讓他隱藏
        footViewHolder.mProgressBar.setVisibility(View.GONE);
        footViewHolder.tv_line1.setVisibility(View.GONE);
        footViewHolder.tv_line2.setVisibility(View.GONE);
        footViewHolder.tv_state.setText("");
      }
      switch (footer_state) {//根據狀態來讓腳布局發生改變
//        case PULL_LOAD_MORE://上拉加載
//          footViewHolder.mProgressBar.setVisibility(View.GONE);
//          footViewHolder.tv_state.setText("上拉加載更多");
//          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("正在加載...");
          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("我是有底線的");
          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的總和,說明是最后一個item,將它設置為腳布局
    if (position + 1 == getItemCount()) {
      return TYPE_FOOTER;
    } else {
      return TYPE_ITEM;
    }
  }

  @Override
  public int getItemCount() {
    return mList != null &#63; 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);
    }
  }

  /**
   * 腳布局的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);

    }
  }

  /**
   * 改變腳布局的狀態的方法,在activity根據請求數據的狀態來改變這個狀態
   *
   * @param state
   */
  public void changeState(int state) {
    this.footer_state = state;
    notifyDataSetChanged();
  }

}

activity中的代碼:

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<String> mList;
  private List<String> list;
  private MyRecyclerAdapter mAdapter;
  LinearLayoutManager linearLayoutManager;
  int lastVisibleItem;
  int page = 0;
  boolean isLoading = false;//用來控制進入getdata()的次數
  int totlePage = 5;//模擬請求的一共的頁數

  @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);
    //給recyclerView添加滑動監聽
    mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
      @Override
      public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        super.onScrollStateChanged(recyclerView, newState);
        /*
        到達底部了,如果不加!isLoading的話到達底部如果還一滑動的話就會一直進入這個方法
        就一直去做請求網絡的操作,這樣的用戶體驗肯定不好.添加一個判斷,每次滑倒底只進行一次網絡請求去請求數據
        當請求完成后,在把isLoading賦值為false,下次滑倒底又能進入這個方法了
         */
        if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mAdapter.getItemCount() && !isLoading) {
          //到達底部之后如果footView的狀態不是正在加載的狀態,就將 他切換成正在加載的狀態
          if (page < totlePage) {
            Log.e("duanlian", "onScrollStateChanged: " + "進來了");
            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);
        //拿到最后一個出現的item的位置
        lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
      }
    });

  }

  /**
   * 模擬請求數據
   */
  private void getData() {
    list = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
      list.add("第" + i + "條");
    }
    mList.addAll(list);
    isLoading = false;
    mAdapter = new MyRecyclerAdapter(this, mList);
    mRecycler.setAdapter(mAdapter);
  }
}

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