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”

• 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.SwipeRefreshLayoutandroid:id="@+id/refreshLayout"android:layout_width="match_parent"android:layout_height="match_parent"><androidx.recyclerview.widget.RecyclerViewandroid: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"><TextViewandroid: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"><TextViewandroid: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Contextprivate int normalType = 0;     // 第一种ViewType，正常的itemprivate int footType = 1;       // 第二种ViewType，底部的提示Viewprivate 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Handlerpublic 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@Overridepublic 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footViewpublic 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@Overridepublic 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);}}@Overridepublic 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));}}@Overridepublic 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() {@Overridepublic void run() {// 隐藏提示条((FootHolder) holder).tips.setVisibility(View.GONE);// 将fadeTips设置truefadeTips = 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falsepublic 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")@Overrideprotected 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() {@Overridepublic void onRefresh() {//上拉刷新，加载第一页refreshLayout.setRefreshing(true);adapter.resetDatas();updateRecyclerView(0, COUNT);mHandler.postDelayed(new Runnable() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic void run() {updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + COUNT);}}, 500);}if (adapter.isFadeTips() == true && lastVisibleItem + 2 == adapter.getItemCount()) {mHandler.postDelayed(new Runnable() {@Overridepublic void run() {updateRecyclerView(adapter.getRealLastPosition(), adapter.getRealLastPosition() + COUNT);}}, 500);}}}@Overridepublic 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;}}