异步加载类
package com.hecx.util;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
/*
* 异步加载图片类
*/
public class AsyncImageLoader {
//SoftReference软引用 ，表示对象通常不会能gc回收内存，则只有在内存短缺的时候才会被回收
private HashMap
public AsyncImageLoader() {
imageCache = new HashMap
}
public Drawable loadDrawable(final String imageUrl, final String srcName, final ImageCallback imageCallback) {
if (imageCache.containsKey(imageUrl)) {
SoftReference
Drawable drawable = softReference.get();
if (drawable != null) {
return drawable;
}
}
//在主线程中处理消息
// 当创建一个新的Handler实例时, 它会绑定到当前线程和消息的队列中,开始分发数据
//另外一个种方式是handler = new Handler(this);this要实现CallBack
final Handler handler = new Handler() {
@Override
public void handleMessage(Message message) {
//表示在主线程加载完后的处理,可以 在这里更新UI
imageCallback.imageLoaded((Drawable) message.obj, imageUrl);
}
};
//这是子线程，在子线程中发送消息
new Thread() {
@Override
public void run() {
final Drawable drawable = loadImageFromUrl(imageUrl, srcName);
imageCache.put(imageUrl, new SoftReference
Message message = handler.obtainMessage(0, drawable);
handler.sendMessage(message);
}
}.start();
return null;
}
public static Drawable loadImageFromUrl(String _url, String srcName) {
// ...
Log.v("TAG", "loadImageFromUrl...");
Drawable drawable = null;
InputStream is = null;
try {
/*
* URL url = new URL(_url); URLConnection conn =
* url.openConnection(); conn.setConnectTimeout(500);
*
* is = conn.getInputStream();
*/
URL url = new URL(_url);
is = (InputStream) url.getContent();
drawable = Drawable.createFromStream(is, srcName);
is.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
Log.v("TAG", "。。。" + e.getMessage());
e.printStackTrace();
} catch (IOException e) {
Log.v("TAG", "。。。" + e.getMessage());
// TODO Auto-generated catch block
e.printStackTrace();
}
return drawable;
}
public interface ImageCallback {
public void imageLoaded(Drawable imageDrawable, String imageUrl);
}
}
自定义adapter
package com.hecx.scrollView;
import java.util.List;
import android.content.Context;
import android.graphics.drawable.Drawable;
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.RelativeLayout;
import android.widget.TextView;
import com.hecx.common.ImageInfo;
import com.hecx.util.AsyncImageLoader;
import com.hecx.util.AsyncImageLoader.ImageCallback;
import com.hecx.zine.R;
/*
* 自定义一个ArrayAdapter
*/
@SuppressWarnings("hiding")
public class ImageInfoAdapter extends ArrayAdapter
/*
* 一般需要定义以下两个变量来存放传入的值
*/
private int resource;
private List
private AsyncImageLoader asyncImageLoader;
private Context context;
private ListView listView;
/*
* 三个参数，一个是context,一个是item布局文件，一个是对象list或对象数组
*/
public ImageInfoAdapter(Context context, int textViewResourceId, List
super(context, textViewResourceId, objects);
this.context = context;
resource = textViewResourceId;
list = objects;
asyncImageLoader = new AsyncImageLoader();
this.listView = listView;
Log.v("TAG", "list.size()=" + list.size());
}
public int getCount() {
return list.size();
}
// 这个方法其实也没什么用，可以随意返回
public long getItemId(int position) {
return position;
}
// 重写getItem方法返回对象
public ImageInfo getItem(int position) {
return (ImageInfo) list.get(position);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Log.v("TAG", "getView...position=" + position);
ImageInfo imageItem = getItem(position);
View rowView = convertView;
ViewHolder viewCache;// = (ViewHolder)convertView.getTag();
if (rowView == null) {
Log.v("TAG", "rowView == null...position=" + position);
LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
rowView = inflater.inflate(resource, null);
viewCache = new ViewHolder(rowView);
rowView.setTag(viewCache);
} else {
viewCache = (ViewHolder) rowView.getTag();
}
ImageView imageView = viewCache.getImageView();
imageView.setTag(imageItem.getImageUrl());
Drawable cachedImage = asyncImageLoader.loadDrawable(imageItem.getImageUrl(), imageItem.getImageUrl(), new ImageCallback() {
public void imageLoaded(Drawable imageDrawable, String imageUrl) {
ImageView imageViewByTag = (ImageView) listView.findViewWithTag(imageUrl);
if (imageViewByTag != null) {
imageViewByTag.setImageDrawable(imageDrawable);
}
}
});
if (cachedImage == null) {
} else {
imageView.setImageDrawable(cachedImage);
}
viewCache.getTitleView().setText(imageItem.getImageTitle());
viewCache.getUrlView().setText(imageItem.getImageUrl());
viewCache.getDescView().setText(imageItem.getImageDesc());
return rowView;
}
public class ViewHolder {
View view;
TextView titleView;
TextView urlView;
TextView descView;
ImageView imageView;
ImageView downloaded_view;
public ViewHolder(View view) {
super();
this.view = view;
}
public TextView getTitleView() {
if (titleView == null) {
titleView = (TextView) view.findViewById(com.hecx.zine.R.id.image_title);
}
return titleView;
}
public TextView getUrlView() {
if (urlView == null) {
urlView = (TextView) view.findViewById(com.hecx.zine.R.id.image_url);
}
return urlView;
}
public TextView getDescView() {
if (descView == null) {
descView = (TextView) view.findViewById(com.hecx.zine.R.id.image_desc);
}
return descView;
}
public ImageView getImageView() {
if (imageView == null) {
imageView = (ImageView) view.findViewById(com.hecx.zine.R.id.image_id);
}
return imageView;
}
public ImageView getDownloaded_view() {
if (downloaded_view == null) {
downloaded_view = (ImageView) view.findViewById(com.hecx.zine.R.id.downloaded_id);
}
return downloaded_view;
}
}
}
异步加载ListView中的每页
package com.hecx.zine.scrollView;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
import android.widget.Toast;
import com.hecx.common.ImageInfo;
import com.hecx.scrollView.ImageDbAdapter;
import com.hecx.scrollView.ImageInfoAdapter;
import com.hecx.util.JsonUtils;
import com.hecx.util.Tools;
import com.hecx.zine.ZineDetailActivity;
public class ScrollActivity extends ListActivity implements _disibledevent=> private int pageCount = 5;//每页大小
//private int allCountd = 0;//当前已经加载的所有大小
private int scrollState;
private boolean loading = false;
private ImageDbAdapter dbAdapter;
/** Called when the activity is first created. */
@Override
public void _disibledevent=> // 1.初始化ListView及其事件
initListView();
// NetTools.isActiveNetworkConnected(MainActivity.this);
}
// 1.初始化ListView及其事件
private void initListView() {
LayoutInflater localLayoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
footer = View.inflate(ScrollActivity.this, com.hecx.zine.R.layout.loading_more_footer, null);
listView = (ListView) this.getListView();// 获取ListActivity下的ListView
imageList = new LinkedList
Log.v("TAG", "imageList.size()=" + imageList.size());
imageAdapter = new ImageInfoAdapter(this, com.hecx.zine.R.layout.item_image, imageList,listView);
//listView.setScrollbarFadingEnabled(false);
listView.addFooterView(footer);
listView.setAdapter(imageAdapter);
listView.setOnScrollListener(this);
DataLoadTask task = new DataLoadTask();
task.execute(null);
}
// _disibledevent=> Log.v("TAG", "if _disibledevent=> if ((!this.loading) && (view.getLastVisiblePosition() == view.getCount() - 1) && (totalItemCount<=5) ) {
Log.v("TAG", "if _disibledevent=> Log.v("TAG", "task="+task);
task.execute(null);
Log.v("TAG", "view.getLastVisiblePosition()=" + view.getLastVisiblePosition());
}
*/
}
// _disibledevent=> if ((!this.loading) && (view.getLastVisiblePosition() == view.getCount() - 1) ) {
Log.v("TAG", "if _disibledevent=> Log.v("TAG", "task="+task);
task.execute(null);
Log.v("TAG", "view.getLastVisiblePosition()=" + view.getLastVisiblePosition());
}
this.scrollState = scrollState;
}
@Override
public boolean _disibledevent=> finish();
return true;
}
return super.onKeyUp(keyCode, event);
}
private void appendMoreData(List
if (paramList != null) {
imageList.addAll(paramList);
this.imageAdapter.notifyDataSetChanged();
}
// 判断是否显示"正在加载..."的进度条(如果新获取的数据为空，或得到的是否还有更多的标识是false，就移动footer，并取消滚动监听器)
//if ((paramList == null) || (!hasMore)) {
if ((paramList == null) || (paramList.size() listView.removeFooterView(footer);
this.footer = null;
listView.setOnScrollListener(null);
}
}
private void saveImageInfos(List
dbAdapter.open();
for(ImageInfo item : _list){
Log.v("TAG", ""+item.getImageId());
dbAdapter.insertData(item.getImageId(), item.getImageTitle(), item.getImageUrl(), item.getImageDesc());
}
dbAdapter.close();
}
@Override
public void _disibledevent=> Toast.makeText(this, "选择了"+imageTitle, Toast.LENGTH_SHORT).show();
*/
//让footer点击无效
if(v == footer ){
return;
}
Bundle bundle = new Bundle();
bundle.putSerializable("imageInfo",(ImageInfo)l.getItemAtPosition(position));
Intent intent = new Intent(this,ZineDetailActivity.class);
intent.putExtras(bundle);
startActivity(intent);
//super.onListItemClick(l, v, position, id);
}
@Override
protected void _disibledevent=> @Override
protected void _disibledevent=> }
@Override
protected Integer doInBackground(Integer... params) {
// TODO Auto-generated method stub
Log.v("TAG", "doInBackground...");
Map paramMap = new HashMap();
paramMap.put("startPos", ""+ScrollActivity.this.currStartPos);
paramMap.put("pageCount", ""+ScrollActivity.this.pageCount);
List _imageList = (List
listMore = Tools.tranList(_imageList);
saveImageInfos(listMore);
return null;
}
@Override
protected void _disibledevent=> //listView.setSelection(MainActivity.this.currStartPos-MainActivity.this.pageCount);
if(listView.getCount()<=5){
//这一段是为了防止第一次加载时出现定位不对的情况
listView.setSelection(0);
}
ScrollActivity.this.loading = false;
ScrollActivity.this.currStartPos = ScrollActivity.this.currStartPos+ScrollActivity.this.pageCount;
}
}
//异步加载数据end
}
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