图片三级缓存+线程池队列

MemoryCache.class

 public class MemoryCache {    public LruCache<String, Bitmap> mMeLruCache;    public MemoryCache(){        int maxMemory=(int) (Runtime.getRuntime().maxMemory()/8);        mMeLruCache=new LruCache<String, Bitmap>(maxMemory){            protected int sizeOf(String key, Bitmap value) {                return value.getRowBytes()*value.getHeight();            }        };    }    public void putBitmap(String url,Bitmap bitmap){        mMeLruCache.put(url, bitmap);    }    public Bitmap getBitmap(String url){        return mMeLruCache.get(url);    }}

NetCache.class

 public class NetCache {    public static final int SUCCESS = 0;    public static final int FAILED = 1;    private Handler mHandler;    private MemoryCache mMemoryCache; // 内存缓存对象    private ExecutorService mExecutorService; // 线程池对象    public NetCache(Handler handler, MemoryCache memoryCache) {        this.mHandler = handler;        this.mMemoryCache = memoryCache;        // 构建一个内部有5个线程的线程池        mExecutorService = Executors.newFixedThreadPool(5);    }    /**     * 获取图片从网络中     * @param url     */    public void getBitmapFromNet(String url, int tag) {//      new Thread(new InternalRunnable(url, tag)).start();        mExecutorService.execute(new InternalRunnable(url, tag));    }    class InternalRunnable implements Runnable {        private String url; // 当前任务需要请求的网络地址        private int tag; // 当前这次请求的图片的标识        public InternalRunnable(String url, int tag) {            this.url = url;            this.tag = tag;        }        @Override        public void run() {            // 访问网络, 抓取图片            HttpURLConnection conn = null;            try {                conn = (HttpURLConnection) new URL(url).openConnection();                conn.setRequestMethod("GET");                conn.setConnectTimeout(5000);                conn.setReadTimeout(5000);                conn.connect();                int responseCode = conn.getResponseCode();                if(responseCode == 200) {                    InputStream is = conn.getInputStream();                    // 把流转换成图片                    Bitmap bm = BitmapFactory.decodeStream(is);                    Message msg = mHandler.obtainMessage();                    msg.obj = bm;                    msg.arg1 = tag;                    msg.what = SUCCESS;                    msg.sendToTarget();                    // 向本地存一份                   LocalCache.putBitmap(url, bm);                    // 向内存存一份                    mMemoryCache.putBitmap(url, bm);                    return;                }            } catch (Exception e) {                e.printStackTrace();            } finally {                if(conn != null) {                    conn.disconnect(); // 断开连接                }            }            mHandler.obtainMessage(FAILED).sendToTarget();        }    }}

LocalCache.class

 public class LocalCache {    private static final File CACHEDIR = new File("/mnt/sdcard/sky");    /**     * 根据url, 向本地存储一张图片     * @param url     * @param bm     */    public static void putBitmap(String url, Bitmap bm) {        try {            String fileName = MD5Encoder.encode(url).substring(0, 10);            if(!CACHEDIR.exists()) {                CACHEDIR.mkdir();            }            File cacheFile = new File(CACHEDIR, fileName);            FileOutputStream fos = new FileOutputStream(cacheFile);            bm.compress(CompressFormat.JPEG, 100, fos);        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * 根据url从本地缓存中取出图片     * @param url     * @return     */    public static Bitmap getBitmap(String url) {        try {            String fileName = MD5Encoder.encode(url).substring(0, 10);            File cacheFile = new File(CACHEDIR, fileName);            if(cacheFile.exists()) {                return BitmapFactory.decodeFile(cacheFile.getPath());            }        } catch (Exception e) {            e.printStackTrace();        }        return null;    }}

ImageLoader.clsaa

 public class ImageLoader {    private NetCache mNetCache;    private MemoryCache mMemoryCache;    public ImageLoader(Handler handler) {        // 定义内存缓存对象        mMemoryCache = new MemoryCache();        // 定义网络缓存对象.        mNetCache = new NetCache(handler, mMemoryCache);    }    /**     * 根据url获取图片     * @param url     * @return     */    public Bitmap getImageFromUrl(String url, int tag) {        // 1. 去内存中取, 取到了之后直接返回.        Bitmap bm = mMemoryCache.getBitmap(url);        if(bm==null){            bm = LocalCache.getBitmap(url);        }        if(bm != null) {            System.out.println("从内存中取");            return bm;        }        // 2. 去本地中取, 取到了之后直接返回.        if(bm != null) {            System.out.println("从本地中取");            return bm;        }        System.out.println("从网络中取");        // 3. 去网络中取, 开启子线程异步抓取, 不能直接返回. 当抓取完毕后, 得到图片, 使用handler发送消息发给调用者.        mNetCache.getBitmapFromNet(url, tag);        return null;    }}

使用方法:

 public class DataAdapter  extends BaseAdapter{    private List<Data> datas;    private ImageLoader imageLoader;    private ListView list;    private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what) {                case NetCache.SUCCESS:                    Bitmap bm = (Bitmap) msg.obj; // 图片                    int tag = msg.arg1; // 当前抓取图片的那个ImageView的tag                    ImageView iv = (ImageView) list.findViewWithTag(tag);                    iv.setImageBitmap(bm);                    break;                case NetCache.FAILED://                  Toast.makeText(mContext, "抓取图片失败", 0).show();                    Log.d("Sky","抓取图片失败");                    break;                default:                    break;            }        }    };    public DataAdapter(List<Data> datas,ListView list) {        super();        this.datas = datas;        this.list=list;        imageLoader=new ImageLoader(handler);    }    @Override    public int getCount() {        // TODO Auto-generated method stub        return datas.size();    }    @Override    public Object getItem(int position) {        // TODO Auto-generated method stub        return datas.get(position);    }    @Override    public long getItemId(int position) {        // TODO Auto-generated method stub        return position;    }     Holder holder=null;    @Override    public View getView(int position, View convertView, ViewGroup parent) {        if (convertView==null) {            convertView= LayoutInflater.from(parent.getContext()).inflate(R.layout.image, null);            holder=new Holder();            holder.imageView1=(ImageView) convertView.findViewById(R.id.imageView1);            convertView.setTag(holder);        }else{            holder=(Holder) convertView.getTag();        }        Bitmap bitmap = imageLoader.getImageFromUrl(datas.get(position).getUrl(), position);        if(bitmap != null) {            // 当前是从内存或者本地取的图片            holder.imageView1.setImageBitmap(bitmap);        }        return convertView;    }    private class Holder{        private ImageView imageView1;        public Holder() {        }    }}