Android 从缓存中读取图片并异步加载的种_Android

Android 从缓存中读取图片并异步加载的类

在新浪微博的微博列表中的图片，为了加速其显示也未了加快程序的响应，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()?{
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????????????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;

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????????public?int?getCount()?{
????????????//?TODO?Auto-generated?method?stub
????????????return?wbList.size();
????????}

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????????public?Object?getItem(int?position)?{
????????????//?TODO?Auto-generated?method?stub
????????????return?wbList.get(position);
????????}

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????????public?long?getItemId(int?position)?{
????????????//?TODO?Auto-generated?method?stub
????????????return?position;
????????}

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????????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;
????????}
????????
????}