Android(安卓)下拉刷新 ListRefresh 从网络加载图片

activity_main布局

<?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_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center"        android:gravity="center"        android:text="TextView" /></LinearLayout>

item布局

<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"    tools:context="com.example.listviewrefresh.MainActivity" >    <com.example.listviewrefresh.MyListView        android:id="@+id/listView"        android:layout_width="match_parent"        android:layout_height="wrap_content"/></RelativeLayout>

package com.example.listviewrefresh;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import android.util.Log;public class Loader {private OnUpdateProgessListener mOnUpdateProgessListener = null;public void setOnUpdateProgessListener(OnUpdateProgessListener l) {this.mOnUpdateProgessListener = l;}public interface OnUpdateProgessListener {public void onUpdateProgress(int count, int total);}public byte[] loadRawDataFromURL(String u) throws Exception {Log.d("下載數據...", u);URL url = new URL(u);HttpURLConnection conn = (HttpURLConnection) url.openConnection();// 总的长度int total = conn.getContentLength();InputStream is = conn.getInputStream();BufferedInputStream bis = new BufferedInputStream(is);ByteArrayOutputStream baos = new ByteArrayOutputStream();final int BUFFER_SIZE = 2048;final int EOF = -1;int c;// 下载的总数计数int count = 0;byte[] buf = new byte[BUFFER_SIZE];while (true) {c = bis.read(buf);if (c == EOF)break;// 每次累加到现在为止我们下载了多少数据，以便于后面计算已经下载的数据占了总数量的百分比count = count + c;// 发布最新的数据，更新随后的进度条显示进度使用if (mOnUpdateProgessListener != null)mOnUpdateProgessListener.onUpdateProgress(count, total);baos.write(buf, 0, c);}conn.disconnect();is.close();byte[] data = baos.toByteArray();baos.flush();Log.d("下載數據完畢", u);return data;}}

package com.example.listviewrefresh;import android.content.Context;import android.util.AttributeSet;import android.widget.AbsListView;import android.widget.ListView;public class MyListView extends ListView {private OnRefreshListener mOnRefreshListener;public interface OnRefreshListener {// 表示下拉见顶刷新回调的接口public void onTop();// 表示上拉见底刷新回调的接口public void onBottom();}public void setOnRefreshListener(OnRefreshListener l) {this.mOnRefreshListener = l;this.setOnScrollListener(new OnScrollListener() {private int firstVisibleItem, visibleItemCount, totalItemCount;@Overridepublic void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount) {this.firstVisibleItem = firstVisibleItem;this.visibleItemCount = visibleItemCount;this.totalItemCount = totalItemCount;}@Overridepublic void onScrollStateChanged(AbsListView view, int scrollState) {if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {// 下拉见顶刷新事件，回调if (firstVisibleItem == 0)mOnRefreshListener.onTop();// 上拉见底部的刷新事件，回调boolean b = (firstVisibleItem + visibleItemCount) == totalItemCount;if (b) {mOnRefreshListener.onBottom();}}}});}public MyListView(Context context, AttributeSet attrs) {super(context, attrs);}}

package com.example.listviewrefresh;import java.util.ArrayList;import java.util.HashMap;import com.example.listviewrefresh.Loader.OnUpdateProgessListener;import com.example.listviewrefresh.MyListView.OnRefreshListener;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.util.Log;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 {// 数据源private ArrayList<HashMap<String, Object>> data;privateString CACHE_URL_KEY="cache_url_key",CACHE_BITMAP="cache_bitmap";private ArrayList<HashMap<String, Object>> cache;private String IMAGE_KEY = "image", TEXT_KEY = "text";private ArrayAdapter adapter;// 加载这个链接的图片资源private String IMAGE_URL = "http://avatar.csdn.net/9/7/A/1_zhangphil.jpg";private MyListView lv;private Activity activity;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);activity = this;Resources res = getResources();cache=new ArrayList<HashMap<String,Object>>();data = 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);}lv = (MyListView) findViewById(R.id.listView);adapter = new MyAdapter(this, -1);lv.setAdapter(adapter);lv.setOnRefreshListener(new OnRefreshListener(){@Overridepublic void onTop() {loadNewData(IMAGE_URL);}@Overridepublic void onBottom() {addBottom();}});}privatevoidloadNewData(String url){Log.d("检查缓存...",url);for(int i=0;i<cache.size();i++){HashMap<String,Object> map=cache.get(i);String u=map.get(CACHE_URL_KEY)+"";if(url.equals(u)){Log.d("发现缓存，直接取出来加载！",url);Bitmap bmp=(Bitmap) map.get(CACHE_BITMAP);addTop(bmp);return;}}Log.d("没有发现缓存，开启线程下载",url);new AddTopAsyncTask().execute(url);}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.item, 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();}}private void addTop(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();}private class AddTopAsyncTask extends AsyncTask<String,Integer,Bitmap> {private ProgressDialog pd;@Overrideprotected void onPreExecute() {pd = new ProgressDialog(activity);pd.setMessage("请稍候，正在加载。。。");pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);pd.show();}@Overrideprotected Bitmap doInBackground(String... params) {String url=params[0];try {Loader loader=new Loader();loader.setOnUpdateProgessListener(new OnUpdateProgessListener(){@Overridepublic void onUpdateProgress(int count, int total) {publishProgress(count,total);}});byte[] bytes=loader.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;} @Override protected void onProgressUpdate(Integer... values) { int count = (Integer) values[0]; int total = (Integer) values[1];  pd.setMax(total); pd.setProgress(count); }@Overrideprotected void onPostExecute(Bitmap result) {pd.dismiss();addTop(result);}}// 底部刷新增加数据private void addBottom() {HashMap<String, Object> map = new HashMap<String, Object>();map.put(IMAGE_KEY, BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher));map.put(TEXT_KEY, data.size());data.add(map);adapter.notifyDataSetChanged();lv.setSelection(ListView.FOCUS_DOWN);}}

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