本文实例讲述了Android实现从缓存中读取图片与异步加载功能类。分享给大家供大家参考，具体如下：
在新浪微博的微博列表中的图片，为了加速其显示也为了加快程序的响应，可以参考该图片异步加载类实现。
public class AsyncImageLoader {
//SoftReference是软引用，是为了更好的为了系统回收变量
private HashMap<String, SoftReference<Drawable>> imageCache;
public AsyncImageLoader() {
imageCache = new HashMap<String, SoftReference<Drawable>>();
}
public Drawable loadDrawable(final String imageUrl,final ImageView imageView, final ImageCallback imageCallback){
if (imageCache.containsKey(imageUrl)) {
//从缓存中获取
SoftReference<Drawable> softReference = imageCache.get(imageUrl);
Drawable drawable = softReference.get();
if (drawable != null) {
return drawable;
}
}
final Handler handler = new Handler() {
public void handleMessage(Message message) {
imageCallback.imageLoaded((Drawable) message.obj, imageView,imageUrl);
}
};
//建立新一个新的线程下载图片
new Thread() {
@Override
public void run() {
Drawable drawable = loadImageFromUrl(imageUrl);
imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));
Message message = handler.obtainMessage(0, drawable);
handler.sendMessage(message);
}
}.start();
return null;
}
public static Drawable loadImageFromUrl(String url){
URL m;
InputStream i = null;
try {
m = new URL(url);
i = (InputStream) m.getContent();
} catch (MalformedURLException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
Drawable d = Drawable.createFromStream(i, "src");
return d;
}
//回调接口
public interface ImageCallback {
public void imageLoaded(Drawable imageDrawable,ImageView imageView, String imageUrl);
}
}
在Adapter中使用的方法为：
public class WeiBoAdapater extends BaseAdapter{
private AsyncImageLoader asyncImageLoader;
@Override
public int getCount() {
// TODO Auto-generated method stub
return wbList.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return wbList.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
convertView = LayoutInflater.from(getApplicationContext()).inflate(R.layout.weibo, null);
WeiBoHolder wh = new WeiBoHolder();
wh.wbicon = (ImageView) convertView.findViewById(R.id.wbicon);
wh.wbtext = (TextView) convertView.findViewById(R.id.wbtext);
wh.wbtime = (TextView) convertView.findViewById(R.id.wbtime);
wh.wbuser = (TextView) convertView.findViewById(R.id.wbuser);
wh.wbimage=(ImageView) convertView.findViewById(R.id.wbimage);
WeiBoInfo wb = wbList.get(position);
if(wb != null)
{
convertView.setTag(wb.getId());
wh.wbuser.setText(wb.getUserName());
wh.wbtime.setText(wb.getTime());
wh.wbtext.setText(wb.getText(), TextView.BufferType.SPANNABLE);
Drawable cachedImage = asyncImageLoader.loadDrawable(wb.getUserIcon(), wh.wbicon, new ImageCallback(){
public void imageLoaded(Drawable imageDrawable,ImageView imageView,String imageUrl){
imageView.setImageDrawable(imageDrawable);
}
});
if (cachedImage == null)
{
wh.wbicon.setImageResource(R.drawable.usericon);
}else{
wh.wbicon.setImageDrawable(cachedImage);
}
}
return convertView;
}
}
更多关于Android相关内容感兴趣的读者可查看本站专题：《Android控件用法总结》、《Android视图View技巧总结》、《Android文件操作技巧汇总》、《Android操作SQLite数据库技巧总结》、《Android操作json格式数据技巧总结》、《Android数据库操作技巧总结》、《Android编程之activity操作技巧总结》、《Android编程开发之SD卡操作方法汇总》、《Android开发入门与进阶教程》及《Android资源操作技巧汇总》
希望本文所述对大家Android程序设计有所帮助。
