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。
