Android 实现 RecyclerView下拉刷新，SwipeRefreshLayout上拉加载

上拉、下拉的效果图如下：

使用步骤

1、在清单文件中添加依赖

implementation ‘com.android.support:recyclerview-v7:27.1.1’
implementation “androidx.swiperefreshlayout:swiperefreshlayout:1.0.0”

在这里插入图片描述

2、main布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
        android:id="@+id/refreshLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</LinearLayout>

item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
    <TextView
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:gravity="center"
        android:textSize="20sp"
        android:textColor="#000000"
        android:text="11"
        android:layout_marginBottom="1dp"/>
</LinearLayout>

footview.xml（底部提示）

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
    <TextView
        android:id="@+id/tips"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:padding="20dp"
        android:textSize="15sp"
        android:layout_marginBottom="1dp"/>
</LinearLayout>

2、MyAdapter

public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private List<String> datas; // 数据源
    private Context context;    // 上下文Context

    private int normalType = 0;     // 第一种ViewType，正常的item
    private int footType = 1;       // 第二种ViewType，底部的提示View

    private boolean hasMore = true;   // 变量，是否有更多数据
    private boolean fadeTips = false; // 变量，是否隐藏了底部的提示

    private Handler mHandler = new Handler(Looper.getMainLooper()); //获取主线程的Handler

    public MyAdapter(List<String> datas, Context context, boolean hasMore) {
        // 初始化变量
        this.datas = datas;
        this.context = context;
        this.hasMore = hasMore;
    }

    // 获取条目数量，之所以要加1是因为增加了一条footView
    @Override
    public int getItemCount() {
        return datas.size() + 1;
    }

    // 自定义方法，获取列表中数据源的最后一个位置，比getItemCount少1，因为不计上footView
    public int getRealLastPosition() {
        return datas.size();
    }


    // 根据条目位置返回ViewType，以供onCreateViewHolder方法内获取不同的Holder
    @Override
    public int getItemViewType(int position) {
        if (position == getItemCount() - 1) {
            return footType;
        } else {
            return normalType;
        }
    }

    // 正常item的ViewHolder，用以缓存findView操作
    class NormalHolder extends RecyclerView.ViewHolder {
        private TextView textView;

        public NormalHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.tv);
        }
    }

    // // 底部footView的ViewHolder，用以缓存findView操作
    class FootHolder extends RecyclerView.ViewHolder {
        private TextView tips;

        public FootHolder(View itemView) {
            super(itemView);
            tips = (TextView) itemView.findViewById(R.id.tips);
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // 根据返回的ViewType，绑定不同的布局文件，这里只有两种
        if (viewType == normalType) {
            return new NormalHolder(LayoutInflater.from(context).inflate(R.layout.item, null));
        } else {
            return new FootHolder(LayoutInflater.from(context).inflate(R.layout.footview, null));
        }
    }

    @Override
    public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
        // 如果是正常的imte，直接设置TextView的值
        if (holder instanceof NormalHolder) {
            ((NormalHolder) holder).textView.setText(datas.get(position));
        } else {
            // 之所以要设置可见，是因为我在没有更多数据时会隐藏了这个footView
            ((FootHolder) holder).tips.setVisibility(View.VISIBLE);
            // 只有获取数据为空时，hasMore为false，所以当我们拉到底部时基本都会首先显示“正在加载更多...”
            if (hasMore == true) {
                // 不隐藏footView提示
                fadeTips = false;
                if (datas.size() > 0) {
                    // 如果查询数据发现增加之后，就显示正在加载更多
                    ((FootHolder) holder).tips.setText("正在加载更多...");
                }
            } else {
                if (datas.size() > 0) {
                    // 如果查询数据发现并没有增加时，就显示没有更多数据了
                    ((FootHolder) holder).tips.setText("没有更多数据了");

                    // 然后通过延时加载模拟网络请求的时间，在500ms后执行
                    mHandler.postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            // 隐藏提示条
                            ((FootHolder) holder).tips.setVisibility(View.GONE);
                            // 将fadeTips设置true
                            fadeTips = true;
                            // hasMore设为true是为了让再次拉到底时，会先显示正在加载更多
                            hasMore = true;
                        }
                    }, 500);
                }
            }
        }
    }

    // 暴露接口，改变fadeTips的方法
    public boolean isFadeTips() {
        return fadeTips;
    }

    // 暴露接口，下拉刷新时，通过暴露方法将数据源置为空
    public void resetDatas() {
        datas = new ArrayList<>();
    }

    // 暴露接口，更新数据源，并修改hasMore的值，如果有增加数据，hasMore为true，否则为false
    public void updateList(List<String> newDatas, boolean hasMore) {
        // 在原有的数据之上增加新数据
        if (newDatas != null) {
            datas.addAll(newDatas);
        }
        this.hasMore = hasMore;
        notifyDataSetChanged();
    }

}

3、MainActivity实现

public class MainActivity extends AppCompatActivity{
    private SwipeRefreshLayout refreshLayout;
    private RecyclerView recyclerView;
    private List<String> list;
    private int lastVisibleItem = 0;
    private final int COUNT = 10;
    private GridLayoutManager mLayoutManager;
    private MyAdapter adapter;
    private Handler mHandler = new Handler(Looper.getMainLooper());

    @SuppressLint("MissingInflatedId")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();//制造假数据
        initView();//初始化布局
        initRefreshLayout();//初始化下拉刷新
        initRecyclerView();//显示recyclerview布局

    }
    private void initData() {
        list = new ArrayList<>();
        for (int i = 1; i <= 40; i++) {
            list.add("测试" + i);
        }
    }
    private void initView() {
        refreshLayout = (SwipeRefreshLayout) findViewById(R.id.refreshLayout);
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);

    }
    private void initRefreshLayout() {
        refreshLayout.setColorSchemeResources(android.R.color.holo_blue_light);
        refreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {//上拉刷新，加载第一页
                refreshLayout.setRefreshing(true);
                adapter.resetDatas();
                updateRecyclerView(0, COUNT);
                mHandler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        refreshLayout.setRefreshing(false);
                    }
                }, 1000);
            }
        });
    }
    private void initRecyclerView() {
        adapter = new MyAdapter(getDatas(0, COUNT), this, getDatas(0, COUNT).size() > 0 ? true : false);
        mLayoutManager = new GridLayoutManager(this, 1);
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.setAdapter(adapter);
        recyclerView.setItemAnimator(new DefaultItemAnimator());

        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    if (adapter.isFadeTips() == false && lastVisibleItem + 1 == adapter.getItemCount()) {
                        mHandler.postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + COUNT);
                            }
                        }, 500);
                    }
                    if (adapter.isFadeTips() == true && lastVisibleItem + 2 == adapter.getItemCount()) {
                        mHandler.postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + COUNT);
                            }
                        }, 500);
                    }
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                lastVisibleItem = mLayoutManager.findLastVisibleItemPosition();
            }
        });
    }
    private void updateRecyclerView(int fromIndex, int toIndex) {
        List<String> newDatas = getDatas(fromIndex, toIndex);
        if (newDatas.size() > 0) {
            adapter.updateList(newDatas, true);
        } else {
            adapter.updateList(null, false);
        }
    }

    //拿到全部数据，加载
    private List<String> getDatas(final int firstIndex, final int lastIndex) {
        List<String> resList = new ArrayList<>();
        for (int i = firstIndex; i < lastIndex; i++) {
            if (i < list.size()) {
                resList.add(list.get(i));
            }
        }
        return resList;
    }
    
}