上拉下拉刷新（2）网络加载图片

 

activity:

<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"    tools:context="com.zhangli.xiala.MainActivity" >    <ListView        android:id="@+id/listView"        android:layout_width="match_parent"        android:layout_height="wrap_content">    </ListView></LinearLayout>

myview:

<?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:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center"        android:gravity="center"        android:src="@drawable/ic_launcher" />    <TextView        android:id="@+id/textView"        android:layout_gravity="center"        android:gravity="center"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></LinearLayout>

UrlDemo:

存放网络加载数据的一个类：

package com.zhangli.xiala;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;public class UrlDemo {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;}}

MainActivity:

 

package com.zhangli.xiala;import java.util.ArrayList;import java.util.HashMap;import android.app.Activity;import android.app.ProgressDialog;import android.content.Context;import android.content.res.Resources;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.AbsListView;import android.widget.AbsListView.OnScrollListener;import android.widget.ArrayAdapter;import android.widget.ImageView;import android.widget.ListView;import android.widget.TextView;public class MainActivity extends Activity {// 数据源private ArrayList<HashMap<String, Object>> data;private String IMAGE_KEY = "image", TEXT_KEY = "text";private ArrayAdapter adapter;private ListView listView;private Activity activity;private String URL_IMAGE = "http://avatar.csdn.net/F/E/F/1_zhangli_.jpg";private String CACHE_URL_KEY = "cache_url_key", CACHE_BITMAP = "cache_bitmap";private ArrayList<HashMap<String, Object>> cache;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);activity = this;Resources res = getResources();data = new ArrayList<HashMap<String, Object>>();cache = new ArrayList<HashMap<String, Object>>();for (int i = 0; i < 20; i++) {HashMap<String, Object> map = new HashMap<String, Object>();map.put(IMAGE_KEY, BitmapFactory.decodeResource(res, R.drawable.ic_launcher));map.put(TEXT_KEY, i);data.add(map);}listView = (ListView) findViewById(R.id.listView);adapter = new MyAdapter(this, -1);listView.setAdapter(adapter);listView.setOnScrollListener(new OnScrollListener() {private int firstVisibleItem, visibleItemCount, totalItemCount;/** * firstVisibleItem:第一条数据 visibleItemCount:屏幕显示的数据数量 * totalItemCount:总的数据数量 */@Overridepublic void onScrollStateChanged(AbsListView view, int scrollState) {// isTop:true表示ListView完全見頂部。isBottom:true，listview完全見底。boolean isTop = false, isBottom = false;if ((visibleItemCount > 0) && (firstVisibleItem == 0)) {if (view.getChildAt(0).getTop() >= 0) {isTop = true;}} else if ((totalItemCount > 0) && (view.getLastVisiblePosition() == totalItemCount - 1)) {if (view.getBottom() == view.getChildAt(view.getChildCount() - 1).getBottom()) {isBottom = true;}}// SCROLL_STATE_IDLE表示刷新完成boolean b = false;if (firstVisibleItem == totalItemCount - visibleItemCount) {b = true;};if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {if (firstVisibleItem == 0 && isTop) {new AddTopAsyncTask().execute(URL_IMAGE);} else if (isBottom && b) {new AddBottomAsyncTask().execute(URL_IMAGE);}}}@Overridepublic void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {this.firstVisibleItem = firstVisibleItem;this.visibleItemCount = visibleItemCount;this.totalItemCount = totalItemCount;}});}private void loadNewDate(String url) {// 检查缓存for (int i = 0; i < cache.size(); i++) {HashMap<String, Object> map = cache.get(i);String u = map.get(CACHE_URL_KEY) + "";if (u.equals(url)) {// 发现有相同的缓存，直接取出来加载Bitmap bmp = (Bitmap) map.get(CACHE_BITMAP);Topadd(bmp);return;}}// 没有法相相同的缓存，开启线程下载new AddTopAsyncTask();}private class MyAdapter extends ArrayAdapter {private LayoutInflater mLayoutInflater;public MyAdapter(Context context, int resource) {super(context, resource);mLayoutInflater = LayoutInflater.from(context);}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {if (convertView == null)convertView = mLayoutInflater.inflate(R.layout.myview, null);ImageView image = (ImageView) convertView.findViewById(R.id.imageView);TextView text = (TextView) convertView.findViewById(R.id.textView);HashMap<String, Object> map = getItem(position);image.setImageBitmap((Bitmap) (map.get(IMAGE_KEY)));text.setText(map.get(TEXT_KEY) + "");return convertView;}@Overridepublic HashMap<String, Object> getItem(int position) {return data.get(position);}@Overridepublic int getCount() {return data.size();}}// 下拉刷新private class AddTopAsyncTask extends AsyncTask<String, Integer, Bitmap> {private ProgressDialog pd;@Overrideprotected void onPreExecute() {pd = new ProgressDialog(activity);pd.setMessage("请稍候，正在下拉刷新加载头部数据。。。");// 设置样式：进度条显示样式pd.setProgressStyle(pd.STYLE_HORIZONTAL);pd.show();}@Overrideprotected void onProgressUpdate(Integer... values) {int value = values[0];pd.setProgress(value);}@Overrideprotected Bitmap doInBackground(String... params) {String url = params[0];for (int i = 0; i < 100; i++) {// 调用上面的onProgressUpdate方法 实现不断增长进度条publishProgress(i);try {Thread.sleep(20);} catch (Exception e) {e.printStackTrace();}}try {byte[] bytes = UrlDemo.loadRawDataFromURL(url);Bitmap bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);// 将加载的数据添加到缓存队列中HashMap<String, Object> map = new HashMap<String, Object>();map.put(CACHE_URL_KEY, url);map.put(CACHE_BITMAP, bmp);cache.add(map);return bmp;} catch (Exception e) {e.printStackTrace();}return null;}@Overrideprotected void onPostExecute(Bitmap result) {pd.dismiss();Topadd(result);}}// 上拉刷新private class AddBottomAsyncTask extends AsyncTask<String, Integer, Bitmap> {private ProgressDialog pd;@Overrideprotected void onPreExecute() {pd = new ProgressDialog(activity);pd.setMessage("请稍候，正在上拉刷新加载头部数据。。。");// 设置样式：进度条显示样式pd.setProgressStyle(pd.STYLE_HORIZONTAL);pd.show();}@Overrideprotected void onProgressUpdate(Integer... values) {int value = values[0];pd.setProgress(value);}@Overrideprotected Bitmap doInBackground(String... params) {String url = params[0];for (int i = 0; i < 100; i++) {// 调用上面的onProgressUpdate方法 实现不断增长进度条publishProgress(i);try {Thread.sleep(20);} catch (Exception e) {e.printStackTrace();}}try {byte[] bytes = UrlDemo.loadRawDataFromURL(url);Bitmap bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);// 将加载的数据添加到缓存队列中HashMap<String, Object> map = new HashMap<String, Object>();map.put(CACHE_URL_KEY, url);map.put(CACHE_BITMAP, bmp);cache.add(map);return bmp;} catch (Exception e) {e.printStackTrace();}return null;}@Overrideprotected void onPostExecute(Bitmap result) {pd.dismiss();bottomadd(result);}}public void Topadd(Bitmap obj) {// Bitmap bmp = (Bitmap) obj;HashMap<String, Object> map = new HashMap<String, Object>();map.put(IMAGE_KEY, obj);map.put(TEXT_KEY, data.size());data.add(0, map);adapter.notifyDataSetChanged();}public void bottomadd(Bitmap obj) {HashMap<String, Object> map = new HashMap<String, Object>();map.put(IMAGE_KEY, obj);map.put(TEXT_KEY, data.size());data.add(map);adapter.notifyDataSetChanged();// 信息保持在最底部listView.setSelection(ListView.FOCUS_DOWN);}}

 

上一篇：上拉下拉刷新（1）地址：http://blog.csdn.net/zhangli_/article/details/50318713