Android ListView异步加载图片

package cn.riddles.activity; import android.app.Activity; import android.os.Bundle; import android.widget.ListView; public class MainActivity extends Activity { private ListView lv; @Override public void onCreate(Bundle savedInstanceState) { super .onCreate(savedInstanceState); setContentView(R.layout.main); lv = (ListView) this .findViewById(R.id.test_lv); lv.setAdapter( new SongListAdapter( this )); } }

package cn.riddles.activity; import android.content.Context; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.TextView; /** * @author riddlezhang 歌曲条目适配器 */ public class SongListAdapter extends BaseAdapter { private static final String TAG = "SongListAdapter" ; private Context mContext; private String[] strings = { "王力宏" , "吴尊" , "何润东" , "金城武" , "吴彦祖" }; private String[] paths = { "http://list.image.baidu.com/t/image_category/galleryimg/menstar/hk/wang_li_hong.jpg" , "http://list.image.baidu.com/t/image_category/galleryimg/menstar/hk/wu_zun.jpg" , "http://list.image.baidu.com/t/image_category/galleryimg/menstar/hk/he_run_dong.jpg" , "http://list.image.baidu.com/t/image_category/galleryimg/menstar/hk/jin_cheng_wu.jpg" , "http://list.image.baidu.com/t/image_category/galleryimg/menstar/hk/wu_yan_zu.jpg" }; public SongListAdapter(Context mContext) { this .mContext = mContext; } public void setmContext(Context mContext) { this .mContext = mContext; } public int getCount() { return paths.length; } public Object getItem( int position) { return position; } public long getItemId( int position) { return position; } public View getView( int position, View convertView, ViewGroup parent) { convertView = LayoutInflater.from(mContext).inflate(R.layout.lv_adapter, null ); ImageView image = (ImageView) convertView.findViewById(R.id.image); TextView songer = (TextView) convertView.findViewById(R.id.songer); image.setTag(paths[position]); songer.setText(strings[position]); new CanvasImageTask().execute(image); //异步加载图片 Log.i(TAG, "execute:" +strings[position]); return convertView; } }

import java.io.InputStream;

import java.lang.ref.SoftReference;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.HashMap;

import android.content.Context;

import android.graphics.drawable.Drawable;

import android.os.AsyncTask;

import android.util.Log;

import android.view.View;

import android.webkit.URLUtil;

/**

* @author riddlezhang 异步加载图片

*/

public class AsyncViewTask extends AsyncTask<View, Void, Drawable> {

private View mView;

private HashMap<String, SoftReference<Drawable>> imageCache;

public AsyncViewTask(Context mContext, String mobileinfo) {

imageCache = new HashMap<String, SoftReference<Drawable>>();

}

protected Drawable doInBackground(View... views) {

Drawable drawable = null ;

View view = views[ 0 ];

if (view.getTag() != null ) {

if (imageCache.containsKey(view.getTag())) {

SoftReference<Drawable> cache = imageCache.get(view.getTag().toString());

drawable = cache.get();

if (drawable != null ) {

return drawable;

}

}

try {

if (URLUtil.isHttpUrl(view.getTag().toString())) { // 如果为网络地址。则连接url下载图片

URL url = new URL(view.getTag().toString());

HttpURLConnection conn = (HttpURLConnection) url.openConnection();

conn.setDoInput( true );

conn.connect();

InputStream stream = conn.getInputStream();

drawable = Drawable.createFromStream(stream, "src" );

stream.close();

} else { // 如果为本地数据，直接解析

drawable = Drawable.createFromPath(view.getTag().toString());

}

} catch (Exception e) {

Log.v( "img" , e.getMessage());

return null ;

}

}

this .mView = view;

return drawable;

if(drawable !=null) {

this .mView.setBackgroundDrawable(drawable);

this .mView = null ;

}

}

}