Android实现从缓存中读取图片与异步加载功能类

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。

用最少的浪费面对现在

Android实现从缓存中读取图片与异步加载功能类

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