利用第三方开源框架 PullToRefreshListView 实现下拉刷新(从网上下载图片)

<LinearLayout 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:orientation="horizontal"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.android.flush.MainActivity" >

<com.handmark.pulltorefresh.library.PullToRefreshListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >

<ImageView
android:id="@+id/imageView"
android:scaleType="fitCenter"
android:layout_width="60dp"
android:layout_height="60dp"/>
<TextView
android:id="@+id/textView"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="60dp"/>

</LinearLayout>

package com.android.flush;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import com.handmark.pulltorefresh.library.PullToRefreshBase;
import com.handmark.pulltorefresh.library.PullToRefreshBase.Mode;
import com.handmark.pulltorefresh.library.PullToRefreshBase.OnRefreshListener;
import com.handmark.pulltorefresh.library.PullToRefreshListView;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {

private final String KEY_IMAGE = "image", KEY_TEXT = "text";
private int count = 0;
private PullToRefreshListView listView;
private ArrayAdapter<String> adapter;
private ArrayList<Map<String, Object>> mDatas;
private Map<String, Object> map;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

listView = (PullToRefreshListView)findViewById(R.id.listView);
mDatas = new ArrayList<Map<String, Object>>();
adapter = new MyAdapter(this, -1);

// 设置刷新模式
listView.setMode(Mode.PULL_FROM_START);
listView.setOnRefreshListener(new OnRefreshListener<ListView>() {
@Override
public void onRefresh(PullToRefreshBase<ListView> refreshView) {
new MyTask().execute();
}
});

listView.setAdapter(adapter);

// 设置提示信息
TextView textView = new TextView(this);
textView.setText("下拉刷新");
listView.setEmptyView(textView);
}

private class MyAdapter extends ArrayAdapter{

private LayoutInflater inflater;

public MyAdapter(Context context, int resource) {
super(context, resource);
inflater = getLayoutInflater();
}

@Override
public int getCount() {
return mDatas.size();
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null)
convertView = inflater.inflate(R.layout.item, null);

HashMap<String, Object> map = (HashMap<String, Object>) (mDatas.get(position));

ImageView image = (ImageView) convertView
.findViewById(R.id.imageView);
image.setImageBitmap((Bitmap) map.get(KEY_IMAGE));

TextView text = (TextView) convertView.findViewById(R.id.textView);
text.setText(map.get(KEY_TEXT) + "");
return convertView;
}

}

private class MyTask extends AsyncTask{

@Override
protected void onPreExecute() {
listView.setRefreshing();
}

@Override
protected void onPostExecute(Object result) {
mDatas.add(0, (Map<String, Object>) result);
listView.setLastUpdatedLabel("更新时间:" + System.currentTimeMillis());

// 通知 adapter 更新，不能少
adapter.notifyDataSetChanged();
listView.onRefreshComplete();
}

@Override
protected Object doInBackground(Object... params) {
try {
Thread.sleep(2000);

byte[] buffer = loadRawDataFromURL("http://pics.sc.chinaz.com/Files/pic/icons128/5982/s1.png");
Bitmap bm =BitmapFactory.decodeByteArray(buffer, 0, buffer.length);
map = new HashMap<String, Object>();
map.put(KEY_IMAGE, bm);
map.put(KEY_TEXT, count++ +"");

return map;

} catch (InterruptedException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}

public static byte[] loadRawDataFromURL(String u) throws Exception {
URL url = new URL(u);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();

InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);

ByteArrayOutputStream baos = new ByteArrayOutputStream();

final int BUFFER_SIZE = 2048;
final int EOF = -1;

int c;
byte[] buf = new byte[BUFFER_SIZE];

while (true) {
c = bis.read(buf);
if (c == EOF)
break;

baos.write(buf, 0, c);
}

conn.disconnect();
is.close();

byte[] data = baos.toByteArray();
baos.flush();

return data;
}
}