RecyclerView 下拉刷新和加载更多

一.SwipeRefreshLayout实现下拉刷新

1.方法API：

setOnRefreshListener(OnRefreshListener):添加下拉刷新监听器 
setRefreshing(boolean):显示或者隐藏刷新进度条 
isRefreshing():检查是否处于刷新状态 
setColorSchemeResources():设置进度条的颜色主题，最多设置四种，以前的setColorScheme()方法已经弃用了。

2.简单使用：

<?xmlversionxmlversion="1.0" encoding="utf-8"?>  
<LinearLayoutxmlns:androidLinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"  
    android:orientation="vertical"android:layout_width="match_parent"  
   android:layout_height="match_parent">  
    <includelayoutincludelayout="@layout/common_top_bar_layout"/>  
   <android.support.v4.widget.SwipeRefreshLayout  
       android:id="@+id/demo_swiperefreshlayout"  
       android:layout_width="fill_parent"  
       android:layout_height="fill_parent"  
        android:scrollbars="vertical"  
        >  
       <android.support.v7.widget.RecyclerView  
           android:id="@+id/demo_recycler"  
           android:layout_width="fill_parent"  
           android:layout_height="fill_parent"  
           ></android.support.v7.widget.RecyclerView>  
   </android.support.v4.widget.SwipeRefreshLayout>  
</LinearLayout>  

Java：

原理：是一个刷新布局，来自兼容包v4可以运行在低版本，控件如果想要支持下拉刷新，只要使用当前布局包裹 
setColorSchemeColors:修改旋转颜色，可以添加多种颜色 
setRefreshing: 是否显示loading状态 
setOnRefreshListener:下拉刷新监听

public class MainActivity extends AppCompatActivity {
    private SwipeRefreshLayout swipeRefreshLayout;
    protected void onCreate(Bundle savedInstanceState) {
                 ·····
   swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.refresh_layout);
        //设置旋转的颜色效果
        swipeRefreshLayout.setColorSchemeColors(Color.GREEN, Color.YELLOW, Color.RED);
        //设置下拉刷新的监听器
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            public void onRefresh() {
                requestData();
            }
        });
    }
    private void requestData() {
        new Handler().postDelayed(new Runnable() {//延时加载
       public void run() {
                String json = "{name:小米}";
                TextView text = (TextView) findViewById(R.id.text);
                text.setText(json);
                swipeRefreshLayout.setRefreshing(false);//关闭显示
            }
        }, 2000);
    }

二.加载更多——上滑加载数据 
思路：

1.滚动到底部 getItemCount()-2 ==bottomPosition 
2.不处理滚动中 
OnScrollListener监听滚动加载的监听器 
int dy 滚动距离，向上滚动为正 
layoutManager.findLastVisibleItemPosition获取处于底部数据的下标 
dy>0与isLoading 都是用来控件灵敏度

public class HomeFragment extends Fragment {
        private SwipeRefreshLayout swipeRefreshLayout;
        private RecyclerView recyclerView;
        private AppAdapter adapter;
        @Override
        public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
                //有一个显示网络状态
                //StateLayout stateLayout  = new StateLayout(container.getContext());
            swipeRefreshLayout = new SwipeRefreshLayout(container.getContext());
            //设置颜色
            swipeRefreshLayout.setColorSchemeColors(Color.GREEN);
            //设置下拉监听
            swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
                @Override
                public void onRefresh() {
                    HttpConnect.get(ApiUrls.HOME+"?index=0", callback);
                }
            });
            recyclerView = new RecyclerView(container.getContext());
            //设置排列规则
            recyclerView.setLayoutManager(new LinearLayoutManager(container.getContext()));
            //预先设置了Noemal视图，但是normal视图没有内容    stateLayout.addNormalView(recyclerView);
            swipeRefreshLayout.addView(recyclerView);
            //发送请求给服务器
            HttpConnect.get(ApiUrls.HOME+"?index=0",callback);
            return swipeRefreshLayout;
        }
        DefaultCallBack callback = new DefaultCallBack() {
            @Override
            public void onStart(int what) {
                swipeRefreshLayout.setRefreshing(true);
            }
            @Override
            public void onFinish(int what) {
                swipeRefreshLayout.setRefreshing(false);
            }
            //拿到数据
            protected void createView(String json) {
                HomeWebInfo info = new Gson().fromJson(json, HomeWebInfo.class);
                //创建控件，设置适配器
                adapter=new AppAdapter(info.list);
                recyclerView.setAdapter(adapter);
                //上滑加载数据
                addLoadMoreList();
            }
        };
        private void addLoadMoreList(){
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener(){
            private boolean isLoading = false;
           //int dy 上下滑动的距离 +数代表往上滑动
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                //判断 是否是排列布局
                RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
                //判断是否是线性排列，并且是否滑动距离
                if(layoutManager instanceof  LinearLayoutManager && dy>0 ){
                    //当前是列表
                    int total = adapter.getItemCount();
                    int lastPosition = total-2;
                    //获取rv 的bottom条目
                    int currLastPosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
                    if(currLastPosition==lastPosition&&!isLoading){      }
                    isLoading=true;
                    Toast.makeText(MyApp.getContext(),"加载更多...",Toast.LENGTH_SHORT).show();
                    new Handler().postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(MyApp.getContext(), "加载成功", Toast.LENGTH_SHORT).show();
                            isLoading=false;
                        }
                    },5000);
                }
            }
        });
      }
  }