学步园

也许之前下拉刷新你可能会用到一些第三方开源库，如PullToRefresh, ActionBar-PullToRefresh等，但现在已经有官方的组件了---SwipeRefreshLayout，SwipeRefreshLayout是Google在support v4 19.1版本的library更新的一个下拉刷新组件，使用起来很方便，可以很方便的实现Google Now的刷新效果。使用官方自带的控件能够保证通用性以及风格。SwipeRefreshLayout是继承ViewGroup，来实现下拉刷新，它可以包含其他组件，使用过后感觉很简单。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.example.myapplication2.app.MainActivity">

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/swip"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <ListView
            android:id="@+id/listview"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            </ListView>
        </android.support.v4.widget.SwipeRefreshLayout>

</RelativeLayout>

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;


public class MainActivity extends ActionBarActivity implements OnRefreshListener{

    private SwipeRefreshLayout swipeRefreshLayout;
    Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            swipeRefreshLayout.setRefreshing(false);
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        swipeRefreshLayout = (SwipeRefreshLayout)findViewById(R.id.swip);
        swipeRefreshLayout.setOnRefreshListener(this);
        swipeRefreshLayout.setColorScheme(android.R.color.holo_blue_bright,
                android.R.color.holo_green_light,
                android.R.color.holo_orange_light,
                android.R.color.holo_red_light);

    }

    @Override
    public void onRefresh() {
        handler.sendEmptyMessageDelayed(1, 5000);
    }
}

在上面的onRefresh()函数中实现获取数据功能以及更新数据，当更新完数据后，调用swipeRefreshLayout.setRefreshing(false);来关闭刷新。