异步加载图片,ListView异步加载图片

首先声明，这看别人的转载的，但是实际使用时有一些疑问。好像线程一直在运行。图片加载完后滚动的时候会出现重载加载
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.net.URLConnection;
import java.util.HashMap;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
/*
* 异步加载图片类
*/
public class AsyncImageLoader {
private HashMap> imageCache;
public AsyncImageLoader() {
imageCache = new HashMap>();
}
public Drawable loadDrawable(final String imageUrl, final String srcName, final ImageCallback imageCallback) {
if (imageCache.containsKey(imageUrl)) {
SoftReference softReference = imageCache.get(imageUrl);
Drawable drawable = softReference.get();
if (drawable != null) {
return drawable;
}
}
final Handler handler = new Handler() {
@Override
public void handleMessage(Message message) {
imageCallback.imageLoaded((Drawable) message.obj, imageUrl);
}
};
new Thread() {
@Override
public void run() {
final Drawable drawable = loadImageFromUrl(imageUrl, srcName);
imageCache.put(imageUrl, new SoftReference(drawable));
Message message = handler.obtainMessage(0, drawable);
handler.sendMessage(message);
}
}.start();
return null;
}
public static Drawable loadImageFromUrl(String _url, String srcName) {
// ...
Drawable drawable = null;
InputStream is = null;
try {
URL url = new URL(_url);
URLConnection conn = url.openConnection();
conn.setConnectTimeout(10 * 1000);
is = conn.getInputStream();
drawable = Drawable.createFromStream(is, srcName);
is.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return drawable;
}
public interface ImageCallback {
public void imageLoaded(Drawable imageDrawable, String imageUrl);
}
}
适配器类:
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 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 objects,ListView listView) {
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) {
RelativeLayout layoutView;
ImageInfo imageItem = getItem(position);
View rowView = convertView;
ViewHolder viewCache = null;// = (ViewHolder)convertView.getTag();
if(rowView == null){
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.getImageTitle(), new ImageCallback() {
public void imageLoaded(Drawable imageDrawable, String imageUrl) {
ImageView imageViewByTag = (ImageView) listView.findViewWithTag(imageUrl);
if (imageViewByTag != null) {
imageViewByTag.setImageDrawable(imageDrawable);
}
}
});
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;
}
}
}

Tags:  js异步加载 异步加载 异步加载图片

延伸阅读

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• 2011-6-28-- 异步加载图片,ListView异步加载图片