Android40_PullToRefresh

PullToRefresh下拉刷新和上拉加载

一、PullToRefresh基础：

（一）、简介：

        在Android开发中有时我们需要访问网络实时刷新数据，比如QQ好友在线状态最新信息，QQ空间需要显示更多的好友动态信息，EOE论坛客户端显示更多的文章帖子信息等。android-pulltorefresh开源项目提供一个向下滑动即刷新列表的功能，将该项目稍作修改即可应用到自己的项目中。

1、下载地址 ：
https://github.com/johannilsson/android-pulltorefresh 
该项目为 Android 应用提供一个向下滑动即刷新列表的功能。

2、工程组成 ：

• 核心文件：PullToRefreshListView.java
  
• OnRefreshListener 监听刷新操作的接口 
  
• onRefresh()刷新函数 在列表头部显示正在进行的刷新操作进度条
  
• onRefreshComplete() 刷新操作完成后，恢复列表常态
  

（二）、ListView中使用PullToRefresh的步骤：【重要】

1、导入文件及其附属资源文件；

2、使用自定义的ListView控件：<包名.PullToRefreshListView>

3、初始化ListView控件：

• pullToRefreshListView_main = (PullToRefreshListView) findViewById(R.id.pullToRefreshListView_main);
  
• listView_main = pullToRefreshListView_main.getRefreshableView();
  

4、PullToRefreshListView设置监听器：

• pullToRefreshListView_main.setOnLastItemVisibleListener();
  
• pullToRefreshListView_main.setOnRefreshListener();
  

5、刷新完成后恢复列表（使头部提示信息消失）：

• pullToRefreshListView_main.onRefreshComplete();

二、《糗事百科》核心实例代码：Volley+PullToRefresh

1、核心代码：

public class MainActivity extends Activity {

private PullToRefreshListView pullToRefreshListView_main;

private ListView listView_main;

private RequestQueue mRequestQueue = null;

private String urlString = "http://m2.qiushibaike.com/article/list/suggest?page=";

private List<Map<String, Object>> totalList = null;

private MyAdapter myAdapter = null;

private int page = 1;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

// 第1步：初始化ListView控件

initView();

// 第 2 步：加载数据

loadData();

}

private void initView() {// 第1步：初始化ListView控件

// 创建RequestQueue

mRequestQueue = Volley.newRequestQueue(this);

pullToRefreshListView_main = (PullToRefreshListView) findViewById(R.id.pullToRefreshListView_main);

listView_main = pullToRefreshListView_main.getRefreshableView();

totalList = new ArrayList<Map<String, Object>>();

myAdapter = new MyAdapter(totalList, mRequestQueue);

listView_main.setAdapter(myAdapter);

pullToRefreshListView_main

.setOnLastItemVisibleListener(new OnLastItemVisibleListener() {

@Override

public void onLastItemVisible() {

page++;

loadData();

}

});

pullToRefreshListView_main

.setOnRefreshListener(new OnRefreshListener() {

@Override

public void onRefresh() {

page = 1;

loadData();

}

});

}

private void loadData() {// 第 2 步：加载数据

StringRequest stringRequest = new StringRequest(urlString + page,

new Response.Listener<String>() {

@Override

public void onResponse(String response) {

if (response != null || "".equals(response)) {

List<Map<String, Object>> list = jsonStringToList(response);

if (list != null) {

totalList.addAll(list);

myAdapter.notifyDataSetChanged();

// 刷新完成后使头部提示信息消失

pullToRefreshListView_main.onRefreshComplete();

}

} else {

setTitle("网络异常！");

}

}

}, new Response.ErrorListener() {

@Override

public void onErrorResponse(VolleyError error) {

}

});

mRequestQueue.add(stringRequest);

}

class MyAdapter extends BaseAdapter {

private List<Map<String, Object>> list = null;

private ImageLoader imageLoader = null;

public MyAdapter(List<Map<String, Object>> list, RequestQueue queue) {

this.list = list;

imageLoader = new ImageLoader(queue, MyImageCache.getInstance());

}

@Override

public int getCount() {

return list.size();

}

@Override

public Object getItem(int position) {

return list.get(position);

}

@Override

public long getItemId(int position) {

return position;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

ViewHolder mHolder;

if (convertView == null) {

mHolder = new ViewHolder();

convertView = getLayoutInflater().inflate(

R.layout.item_listview_main, parent, false);

mHolder.textView_item_content = (TextView) convertView

.findViewById(R.id.textView_item_content);

mHolder.textView_item_commentcount = (TextView) convertView

.findViewById(R.id.textView_item_commentcount);

mHolder.textView_item_login = (TextView) convertView

.findViewById(R.id.textView_item_login);

mHolder.networkImageView_item_cover = (NetworkImageView) convertView

.findViewById(R.id.networkImageView_item_cover);

convertView.setTag(mHolder);

} else {

mHolder = (ViewHolder) convertView.getTag();

}

mHolder.textView_item_content.setText(list.get(position)

.get("content").toString());

mHolder.textView_item_commentcount.setText(list.get(position)

.get("comments_count").toString());

mHolder.textView_item_login.setText(list.get(position).get("login")

.toString());

// 第3步：开始异步加载图片

final String imgUrlString = getImageUrl(list.get(position)

.get("image").toString());

if (imgUrlString.equals("")) {

mHolder.networkImageView_item_cover

.setImageResource(R.drawable.empty);

} else {

mHolder.networkImageView_item_cover

.setDefaultImageResId(R.drawable.empty);

mHolder.networkImageView_item_cover

.setErrorImageResId(R.drawable.ic_launcher);

mHolder.networkImageView_item_cover.setImageUrl(imgUrlString,

imageLoader);

// 单击监听，实现打开大图

mHolder.networkImageView_item_cover

.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

Intent intent = new Intent();

intent.setClass(MainActivity.this,

BitmapshowActivity.class);

Bundle bundle = new Bundle();

bundle.putString("imgUrlString", imgUrlString);

intent.putExtras(bundle);

startActivity(intent);

}

});

}

return convertView;

}

class ViewHolder {

private NetworkImageView networkImageView_item_cover;

private TextView textView_item_content;

private TextView textView_item_login;

private TextView textView_item_commentcount;

}

}

// 根据json解析获取到的图片名称，生成该图片的url地址

private String getImageUrl(String imageName) {

String prefixUrlString = "http://pic.qiushibaike.com/system/pictures/";

Pattern pattern = Pattern.compile("(\\d{4})\\d+");

Matcher matcher = pattern.matcher(imageName);

StringBuilder url = new StringBuilder();

if (matcher.find()) {

url.append(prefixUrlString).append(matcher.group(1)).append('/')

.append(matcher.group(0)).append("/small/")

.append(imageName);

return url.toString();

} else {

return "";

}

}

private List<Map<String, Object>> jsonStringToList(String jsonString) {

List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();

try {

JSONObject jsonObject = new JSONObject(jsonString);

JSONArray jsonArray_items = jsonObject.getJSONArray("items");

for (int i = 0; i < jsonArray_items.length(); i++) {

JSONObject jsonObject_item = jsonArray_items.getJSONObject(i);

Map<String, Object> map = new HashMap<String, Object>();

map.put("image", jsonObject_item.getString("image"));

map.put("content", jsonObject_item.getString("content"));

map.put("comments_count",

jsonObject_item.getString("comments_count"));

JSONObject jsonObject_user = jsonObject_item

.optJSONObject("user");

if (jsonObject_user == null) {

map.put("login", "【 匿名 】");

} else {

map.put("login", "【 " + jsonObject_user.getString("login")

+ " 】");

}

list.add(map);

}

return list;

} catch (JSONException e) {

e.printStackTrace();

}

return null;

}

static class MyImageCache implements ImageCache {

private static LruCache<String, Bitmap> lruCache = null;

private static MyImageCache myImageCache = null;

private MyImageCache() {

int memorySize = (int) Runtime.getRuntime().maxMemory();

int lruCacheSize = memorySize / 8;

lruCache = new LruCache<String, Bitmap>(lruCacheSize) {

@Override

protected int sizeOf(String key, Bitmap value) {

return value.getRowBytes() * value.getHeight();

}

};

}

public static MyImageCache getInstance() {

if (myImageCache == null) {

myImageCache = new MyImageCache();

}

return myImageCache;

}

@Override

public Bitmap getBitmap(String url) {

return lruCache.get(url);

}

@Override

public void putBitmap(String url, Bitmap bitmap) {

lruCache.put(url, bitmap);

}

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

}

}

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