Material Design 实战 之第五弹 —— 下拉刷新（SwipeRefreshLayout）

SwipeRefreshLayout

    1.SwipeRefreshLayout即是实现下拉刷新功能的核心类，它由support-v4库提供的；

    2.把想要实现下拉刷新功能的控件放置到SwipeRefreshLayout里边，即可迅速让这个控件支持下拉刷新了；

    3.接下来在对应的java代码中处理具体的刷新逻辑：
        3.1 实例化SwipeRefreshLayout；
        3.2 调用setcolorSchemeResources()方法来设置下拉刷新进度条的颜色；
        3.3 调用setonRefreshListener()方法设置一个下拉刷新的监听器， 
            传入一个SwipeRefreshLayout.OnRefreshListener()并重写onRefresh()来处理具体的刷新逻辑；

        3.4 刷新逻辑使用中可以使用如下多线程结构：
         new Thread(new Runnable() {
            @Override
            public void run() {
                try{

                }catch (InterruptedException e){
                    e.printStackTrace();
                }
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {

                    }
                });
            }
        }).start();

    其中try中书写耗时操作，然后在 runOnUiThread() 中的 run() 中获取到数据，
    并adapter.notifyDataSetChanged()调用刷新数据；
    最后调用swipeRefreshLayout的setRefreshing()并传入false，表示刷新事件结束同时隐藏刷新进度条；

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

       <android.support.design.widget.AppBarLayout
           android:layout_width="match_parent"
           android:layout_height="wrap_content">
           <android.support.v7.widget.Toolbar
               android:id="@+id/toolbar"
               android:layout_width="match_parent"
               android:layout_height="?attr/actionBarSize"
               android:background="?attr/colorPrimary"
               android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
               app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
               app:layout_scrollFlags="scroll|enterAlways|snap"/>
       </android.support.design.widget.AppBarLayout>

        <android.support.v4.widget.SwipeRefreshLayout
            android:id="@+id/swipe_refresh"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior = "@string/appbar_scrolling_view_behavior">
            <android.support.v7.widget.RecyclerView
                android:id="@+id/recycler_view"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </android.support.v4.widget.SwipeRefreshLayout>

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_margin="16dp"
            android:src="@drawable/ic_done"
            app:elevation="8dp"/>
    </android.support.design.widget.CoordinatorLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/nav_menu"
        app:headerLayout="@layout/nav_header">

    </android.support.design.widget.NavigationView>

</android.support.v4.widget.DrawerLayout>

//下拉刷新
    private SwipeRefreshLayout swipeRefresh;
------------------------------------


 //下拉刷新逻辑处理
        swipeRefresh = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh);
        swipeRefresh.setColorSchemeResources(R.color.colorPrimary);
        swipeRefresh.setOnRefreshListener(new SwipeRefreshLayout.
                OnRefreshListener(){
            @Override
            public void onRefresh() {
                refreshFruits();
            }
        });
------------------------------------

 private void refreshFruits(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                try{
                    Thread.sleep(2000);
                }catch (InterruptedException e){
                    e.printStackTrace();
                }
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        initFruits();
                        adapter.notifyDataSetChanged();
                        swipeRefresh.setRefreshing(false);
                    }
                });
            }
        }).start();
    }