Android 异步加载图片，使用LruCache和SD卡或手机缓存，效果非常的流畅

package com.example.asyncimageloader;  
 
import java.io.File;  
import java.io.FileOutputStream;  
import java.io.IOException;  
 
import android.content.Context;  
import android.graphics.Bitmap;  
import android.graphics.Bitmap.CompressFormat;  
import android.graphics.BitmapFactory;  
import android.os.Environment;  
 
public class FileUtils {  
 /** 
     * sd卡的根目录 
     */ 
 private static String mSdRootPath = Environment.getExternalStorageDirectory().getPath();  
 /** 
     * 手机的缓存根目录 
     */ 
 private static String mDataRootPath = null;  
 /** 
     * 保存Image的目录名 
     */ 
 private final static String FOLDER_NAME = "/AndroidImage";  
 
 
 public FileUtils(Context context){  
        mDataRootPath = context.getCacheDir().getPath();  
    }  
 
 
 /** 
     * 获取储存Image的目录 
     * @return 
     */ 
 private String getStorageDirectory(){  
 return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED) ?  
                mSdRootPath + FOLDER_NAME : mDataRootPath + FOLDER_NAME;  
    }  
 
 /** 
     * 保存Image的方法，有sd卡存储到sd卡，没有就存储到手机目录 
     * @param fileName  
     * @param bitmap    
     * @throws IOException 
     */ 
 public void savaBitmap(String fileName, Bitmap bitmap) throws IOException{  
 if(bitmap == null){  
 return;  
        }  
        String path = getStorageDirectory();  
        File folderFile = new File(path);  
 if(!folderFile.exists()){  
            folderFile.mkdir();  
        }  
        File file = new File(path + File.separator + fileName);  
        file.createNewFile();  
        FileOutputStream fos = new FileOutputStream(file);  
        bitmap.compress(CompressFormat.JPEG, 100, fos);  
        fos.flush();  
        fos.close();  
    }  
 
 /** 
     * 从手机或者sd卡获取Bitmap 
     * @param fileName 
     * @return 
     */ 
 public Bitmap getBitmap(String fileName){  
 return BitmapFactory.decodeFile(getStorageDirectory() + File.separator + fileName);  
    }  
 
 /** 
     * 判断文件是否存在 
     * @param fileName 
     * @return 
     */ 
 public boolean isFileExists(String fileName){  
 return new File(getStorageDirectory() + File.separator + fileName).exists();  
    }  
 
 /** 
     * 获取文件的大小 
     * @param fileName 
     * @return 
     */ 
 public long getFileSize(String fileName) {  
 return new File(getStorageDirectory() + File.separator + fileName).length();  
    }  
 
 
 /** 
     * 删除SD卡或者手机的缓存图片和目录 
     */ 
 public void deleteFile() {  
        File dirFile = new File(getStorageDirectory());  
 if(! dirFile.exists()){  
 return;  
        }  
 if (dirFile.isDirectory()) {  
            String[] children = dirFile.list();  
 for (int i = 0; i < children.length; i++) {  
 new File(dirFile, children[i]).delete();  
            }  
        }  
 
        dirFile.delete();  
    }  
}<span style="font-family:Times New Roman;font-size:14px;">  
</span>  

package com.example.asyncimageloader;  
 
public class Images {  
 
 public final static String[] imageThumbUrls = new String[] {  
 "https://lh6.googleusercontent.com/-55osAWw3x0Q/URquUtcFr5I/AAAAAAAAAbs/rWlj1RUKrYI/s160-c/A%252520Photographer.jpg",  
 "https://lh4.googleusercontent.com/--dq8niRp7W4/URquVgmXvgI/AAAAAAAAAbs/-gnuLQfNnBA/s160-c/A%252520Song%252520of%252520Ice%252520and%252520Fire.jpg",  
 "https://lh5.googleusercontent.com/-7qZeDtRKFKc/URquWZT1gOI/AAAAAAAAAbs/hqWgteyNXsg/s160-c/Another%252520Rockaway%252520Sunset.jpg",  
 "https://lh3.googleusercontent.com/--L0Km39l5J8/URquXHGcdNI/AAAAAAAAAbs/3ZrSJNrSomQ/s160-c/Antelope%252520Butte.jpg",  
 "https://lh6.googleusercontent.com/-8HO-4vIFnlw/URquZnsFgtI/AAAAAAAAAbs/WT8jViTF7vw/s160-c/Antelope%252520Hallway.jpg",  
 "https://lh4.googleusercontent.com/-WIuWgVcU3Qw/URqubRVcj4I/AAAAAAAAAbs/YvbwgGjwdIQ/s160-c/Antelope%252520Walls.jpg",  
 "https://lh6.googleusercontent.com/-UBmLbPELvoQ/URqucCdv0kI/AAAAAAAAAbs/IdNhr2VQoQs/s160-c/Apre%2525CC%252580s%252520la%252520Pluie.jpg",  
 "https://lh3.googleusercontent.com/-s-AFpvgSeew/URquc6dF-JI/AAAAAAAAAbs/Mt3xNGRUd68/s160-c/Backlit%252520Cloud.jpg",  
 "https://lh5.googleusercontent.com/-bvmif9a9YOQ/URquea3heHI/AAAAAAAAAbs/rcr6wyeQtAo/s160-c/Bee%252520and%252520Flower.jpg",  
 "https://lh5.googleusercontent.com/-n7mdm7I7FGs/URqueT_BT-I/AAAAAAAAAbs/9MYmXlmpSAo/s160-c/Bonzai%252520Rock%252520Sunset.jpg",  
 "https://lh6.googleusercontent.com/-4CN4X4t0M1k/URqufPozWzI/AAAAAAAAAbs/8wK41lg1KPs/s160-c/Caterpillar.jpg",  
 "https://lh3.googleusercontent.com/-rrFnVC8xQEg/URqufdrLBaI/AAAAAAAAAbs/s69WYy_fl1E/s160-c/Chess.jpg",  
 "https://lh5.googleusercontent.com/-WVpRptWH8Yw/URqugh-QmDI/AAAAAAAAAbs/E-MgBgtlUWU/s160-c/Chihuly.jpg",  
 "https://lh5.googleusercontent.com/-0BDXkYmckbo/URquhKFW84I/AAAAAAAAAbs/ogQtHCTk2JQ/s160-c/Closed%252520Door.jpg",  
 "https://lh3.googleusercontent.com/-PyggXXZRykM/URquh-kVvoI/AAAAAAAAAbs/hFtDwhtrHHQ/s160-c/Colorado%252520River%252520Sunset.jpg",  
 "https://lh3.googleusercontent.com/-ZAs4dNZtALc/URquikvOCWI/AAAAAAAAAbs/DXz4h3dll1Y/s160-c/Colors%252520of%252520Autumn.jpg",  
 "https://lh4.googleusercontent.com/-GztnWEIiMz8/URqukVCU7bI/AAAAAAAAAbs/jo2Hjv6MZ6M/s160-c/Countryside.jpg",  
 "https://lh4.googleusercontent.com/-bEg9EZ9QoiM/URquklz3FGI/AAAAAAAAAbs/UUuv8Ac2BaE/s160-c/Death%252520Valley%252520-%252520Dunes.jpg",  
 "https://lh6.googleusercontent.com/-ijQJ8W68tEE/URqulGkvFEI/AAAAAAAAAbs/zPXvIwi_rFw/s160-c/Delicate%252520Arch.jpg",  
 "https://lh5.googleusercontent.com/-Oh8mMy2ieng/URqullDwehI/AAAAAAAAAbs/TbdeEfsaIZY/s160-c/Despair.jpg",  
 "https://lh5.googleusercontent.com/-gl0y4UiAOlk/URqumC_KjBI/AAAAAAAAAbs/PM1eT7dn4oo/s160-c/Eagle%252520Fall%252520Sunrise.jpg",  
 "https://lh3.googleusercontent.com/-hYYHd2_vXPQ/URqumtJa9eI/AAAAAAAAAbs/wAalXVkbSh0/s160-c/Electric%252520Storm.jpg",  
 "https://lh5.googleusercontent.com/-PyY_yiyjPTo/URqunUOhHFI/AAAAAAAAAbs/azZoULNuJXc/s160-c/False%252520Kiva.jpg",  
 "https://lh6.googleusercontent.com/-PYvLVdvXywk/URqunwd8hfI/AAAAAAAAAbs/qiMwgkFvf6I/s160-c/Fitzgerald%252520Streaks.jpg",  
 "https://lh4.googleusercontent.com/-KIR_UobIIqY/URquoCZ9SlI/AAAAAAAAAbs/Y4d4q8sXu4c/s160-c/Foggy%252520Sunset.jpg",  
 "https://lh6.googleusercontent.com/-9lzOk_OWZH0/URquoo4xYoI/AAAAAAAAAbs/AwgzHtNVCwU/s160-c/Frantic.jpg",  
 "https://lh3.googleusercontent.com/-0X3JNaKaz48/URqupH78wpI/AAAAAAAAAbs/lHXxu_zbH8s/s160-c/Golden%252520Gate%252520Afternoon.jpg",  
 "https://lh6.googleusercontent.com/-95sb5ag7ABc/URqupl95RDI/AAAAAAAAAbs/g73R20iVTRA/s160-c/Golden%252520Gate%252520Fog.jpg",  
 "https://lh3.googleusercontent.com/-JB9v6rtgHhk/URqup21F-zI/AAAAAAAAAbs/64Fb8qMZWXk/s160-c/Golden%252520Grass.jpg",  
 "https://lh4.googleusercontent.com/-EIBGfnuLtII/URquqVHwaRI/AAAAAAAAAbs/FA4McV2u8VE/s160-c/Grand%252520Teton.jpg",  
 "https://lh4.googleusercontent.com/-WoMxZvmN9nY/URquq1v2AoI/AAAAAAAAAbs/grj5uMhL6NA/s160-c/Grass%252520Closeup.jpg",  
 "https://lh3.googleusercontent.com/-6hZiEHXx64Q/URqurxvNdqI/AAAAAAAAAbs/kWMXM3o5OVI/s160-c/Green%252520Grass.jpg",  
 "https://lh5.googleusercontent.com/-6LVb9OXtQ60/URquteBFuKI/AAAAAAAAAbs/4F4kRgecwFs/s160-c/Hanging%252520Leaf.jpg",  
 "https://lh4.googleusercontent.com/-zAvf__52ONk/URqutT_IuxI/AAAAAAAAAbs/D_bcuc0thoU/s160-c/Highway%2525201.jpg",  
 "https://lh6.googleusercontent.com/-H4SrUg615rA/URquuL27fXI/AAAAAAAAAbs/4aEqJfiMsOU/s160-c/Horseshoe%252520Bend%252520Sunset.jpg",  
 "https://lh4.googleusercontent.com/-JhFi4fb_Pqw/URquuX-QXbI/AAAAAAAAAbs/IXpYUxuweYM/s160-c/Horseshoe%252520Bend.jpg",  
 "https://lh5.googleusercontent.com/-UGgssvFRJ7g/URquueyJzGI/AAAAAAAAAbs/yYIBlLT0toM/s160-c/Into%252520the%252520Blue.jpg",  
 "https://lh3.googleusercontent.com/-CH7KoupI7uI/URquu0FF__I/AAAAAAAAAbs/R7GDmI7v_G0/s160-c/Jelly%252520Fish%2525202.jpg",  
 "https://lh4.googleusercontent.com/-pwuuw6yhg8U/URquvPxR3FI/AAAAAAAAAbs/VNGk6f-tsGE/s160-c/Jelly%252520Fish%2525203.jpg",  
 "https://lh5.googleusercontent.com/-GoUQVw1fnFw/URquv6xbC0I/AAAAAAAAAbs/zEUVTQQ43Zc/s160-c/Kauai.jpg",  
 "https://lh6.googleusercontent.com/-8QdYYQEpYjw/URquwvdh88I/AAAAAAAAAbs/cktDy-ysfHo/s160-c/Kyoto%252520Sunset.jpg",  
 "https://lh4.googleusercontent.com/-vPeekyDjOE0/URquwzJ28qI/AAAAAAAAAbs/qxcyXULsZrg/s160-c/Lake%252520Tahoe%252520Colors.jpg",  
 "https://lh4.googleusercontent.com/-xBPxWpD4yxU/URquxWHk8AI/AAAAAAAAAbs/ARDPeDYPiMY/s160-c/Lava%252520from%252520the%252520Sky.jpg",  
 "https://lh3.googleusercontent.com/-897VXrJB6RE/URquxxxd-5I/AAAAAAAAAbs/j-Cz4T4YvIw/s160-c/Leica%25252050mm%252520Summilux.jpg",  
 "https://lh5.googleusercontent.com/-qSJ4D4iXzGo/URquyDWiJ1I/AAAAAAAAAbs/k2pBXeWehOA/s160-c/Leica%25252050mm%252520Summilux.jpg",  
 "https://lh6.googleusercontent.com/-dwlPg83vzLg/URquylTVuFI/AAAAAAAAAbs/G6SyQ8b4YsI/s160-c/Leica%252520M8%252520%252528Front%252529.jpg",  
 "https://lh3.googleusercontent.com/-R3_EYAyJvfk/URquzQBv8eI/AAAAAAAAAbs/b9xhpUM3pEI/s160-c/Light%252520to%252520Sand.jpg",  
 "https://lh3.googleusercontent.com/-fHY5h67QPi0/URqu0Cp4J1I/AAAAAAAAAbs/0lG6m94Z6vM/s160-c/Little%252520Bit%252520of%252520Paradise.jpg",  
 "https://lh5.googleusercontent.com/-TzF_LwrCnRM/URqu0RddPOI/AAAAAAAAAbs/gaj2dLiuX0s/s160-c/Lone%252520Pine%252520Sunset.jpg",  
 "https://lh3.googleusercontent.com/-4HdpJ4_DXU4/URqu046dJ9I/AAAAAAAAAbs/eBOodtk2_uk/s160-c/Lonely%252520Rock.jpg",  
 "https://lh6.googleusercontent.com/-erbF--z-W4s/URqu1ajSLkI/AAAAAAAAAbs/xjDCDO1INzM/s160-c/Longue%252520Vue.jpg",  
 "https://lh6.googleusercontent.com/-0CXJRdJaqvc/URqu1opNZNI/AAAAAAAAAbs/PFB2oPUU7Lk/s160-c/Look%252520Me%252520in%252520the%252520Eye.jpg",  
 "https://lh3.googleusercontent.com/-D_5lNxnDN6g/URqu2Tk7HVI/AAAAAAAAAbs/p0ddca9W__Y/s160-c/Lost%252520in%252520a%252520Field.jpg",  
 "https://lh6.googleusercontent.com/-flsqwMrIk2Q/URqu24PcmjI/AAAAAAAAAbs/5ocIH85XofM/s160-c/Marshall%252520Beach%252520Sunset.jpg",  
 "https://lh4.googleusercontent.com/-Y4lgryEVTmU/URqu28kG3gI/AAAAAAAAAbs/OjXpekqtbJ4/s160-c/Mono%252520Lake%252520Blue.jpg",  
 "https://lh4.googleusercontent.com/-AaHAJPmcGYA/URqu3PIldHI/AAAAAAAAAbs/lcTqk1SIcRs/s160-c/Monument%252520Valley%252520Overlook.jpg",  
 "https://lh4.googleusercontent.com/-vKxfdQ83dQA/URqu31Yq_BI/AAAAAAAAAbs/OUoGk_2AyfM/s160-c/Moving%252520Rock.jpg",  
 "https://lh5.googleusercontent.com/-CG62QiPpWXg/URqu4ia4vRI/AAAAAAAAAbs/0YOdqLAlcAc/s160-c/Napali%252520Coast.jpg",  
 "https://lh6.googleusercontent.com/-wdGrP5PMmJQ/URqu5PZvn7I/AAAAAAAAAbs/m0abEcdPXe4/s160-c/One%252520Wheel.jpg",  
 "https://lh6.googleusercontent.com/-6WS5DoCGuOA/URqu5qx1UgI/AAAAAAAAAbs/giMw2ixPvrY/s160-c/Open%252520Sky.jpg",  
 "https://lh6.googleusercontent.com/-u8EHKj8G8GQ/URqu55sM6yI/AAAAAAAAAbs/lIXX_GlTdmI/s160-c/Orange%252520Sunset.jpg",  
 "https://lh6.googleusercontent.com/-74Z5qj4bTDE/URqu6LSrJrI/AAAAAAAAAbs/XzmVkw90szQ/s160-c/Orchid.jpg",  
 "https://lh6.googleusercontent.com/-lEQE4h6TePE/URqu6t_lSkI/AAAAAAAAAbs/zvGYKOea_qY/s160-c/Over%252520there.jpg",  
 "https://lh5.googleusercontent.com/-cauH-53JH2M/URqu66v_USI/AAAAAAAAAbs/EucwwqclfKQ/s160-c/Plumes.jpg",  
 "https://lh3.googleusercontent.com/-eDLT2jHDoy4/URqu7axzkAI/AAAAAAAAAbs/iVZE-xJ7lZs/s160-c/Rainbokeh.jpg",  
 "https://lh5.googleusercontent.com/-j1NLqEFIyco/URqu8L1CGcI/AAAAAAAAAbs/aqZkgX66zlI/s160-c/Rainbow.jpg",  
 "https://lh5.googleusercontent.com/-DRnqmK0t4VU/URqu8XYN9yI/AAAAAAAAAbs/LgvF_592WLU/s160-c/Rice%252520Fields.jpg",  
 "https://lh3.googleusercontent.com/-hwh1v3EOGcQ/URqu8qOaKwI/AAAAAAAAAbs/IljRJRnbJGw/s160-c/Rockaway%252520Fire%252520Sky.jpg",  
 "https://lh5.googleusercontent.com/-wjV6FQk7tlk/URqu9jCQ8sI/AAAAAAAAAbs/RyYUpdo-c9o/s160-c/Rockaway%252520Flow.jpg",  
 "https://lh6.googleusercontent.com/-6cAXNfo7D20/URqu-BdzgPI/AAAAAAAAAbs/OmsYllzJqwo/s160-c/Rockaway%252520Sunset%252520Sky.jpg",  
 "https://lh3.googleusercontent.com/-sl8fpGPS-RE/URqu_BOkfgI/AAAAAAAAAbs/Dg2Fv-JxOeg/s160-c/Russian%252520Ridge%252520Sunset.jpg",  
 "https://lh6.googleusercontent.com/-gVtY36mMBIg/URqu_q91lkI/AAAAAAAAAbs/3CiFMBcy5MA/s160-c/Rust%252520Knot.jpg",  
 "https://lh6.googleusercontent.com/-GHeImuHqJBE/URqu_FKfVLI/AAAAAAAAAbs/axuEJeqam7Q/s160-c/Sailing%252520Stones.jpg",  
 "https://lh3.googleusercontent.com/-hBbYZjTOwGc/URqu_ycpIrI/AAAAAAAAAbs/nAdJUXnGJYE/s160-c/Seahorse.jpg",  
 "https://lh3.googleusercontent.com/-Iwi6-i6IexY/URqvAYZHsVI/AAAAAAAAAbs/5ETWl4qXsFE/s160-c/Shinjuku%252520Street.jpg",  
 "https://lh6.googleusercontent.com/-amhnySTM_MY/URqvAlb5KoI/AAAAAAAAAbs/pFCFgzlKsn0/s160-c/Sierra%252520Heavens.jpg",  
 "https://lh5.googleusercontent.com/-dJgjepFrYSo/URqvBVJZrAI/AAAAAAAAAbs/v-F5QWpYO6s/s160-c/Sierra%252520Sunset.jpg",  
 "https://lh4.googleusercontent.com/-Z4zGiC5nWdc/URqvBdEwivI/AAAAAAAAAbs/ZRZR1VJ84QA/s160-c/Sin%252520Lights.jpg",  
 "https://lh4.googleusercontent.com/-_0cYiWW8ccY/URqvBz3iM4I/AAAAAAAAAbs/9N_Wq8MhLTY/s160-c/Starry%252520Lake.jpg",  
 "https://lh3.googleusercontent.com/-A9LMoRyuQUA/URqvCYx_JoI/AAAAAAAAAbs/s7sde1Bz9cI/s160-c/Starry%252520Night.jpg",  
 "https://lh3.googleusercontent.com/-KtLJ3k858eY/URqvC_2h_bI/AAAAAAAAAbs/zzEBImwDA_g/s160-c/Stream.jpg",  
 "https://lh5.googleusercontent.com/-dFB7Lad6RcA/URqvDUftwWI/AAAAAAAAAbs/BrhoUtXTN7o/s160-c/Strip%252520Sunset.jpg",  
 "https://lh5.googleusercontent.com/-at6apgFiN20/URqvDyffUZI/AAAAAAAAAbs/clABCx171bE/s160-c/Sunset%252520Hills.jpg",  
 "https://lh4.googleusercontent.com/-7-EHhtQthII/URqvEYTk4vI/AAAAAAAAAbs/QSJZoB3YjVg/s160-c/Tenaya%252520Lake%2525202.jpg",  
 "https://lh6.googleusercontent.com/-8MrjV_a-Pok/URqvFC5repI/AAAAAAAAAbs/9inKTg9fbCE/s160-c/Tenaya%252520Lake.jpg",  
 "https://lh5.googleusercontent.com/-B1HW-z4zwao/URqvFWYRwUI/AAAAAAAAAbs/8Peli53Bs8I/s160-c/The%252520Cave%252520BW.jpg",  
 "https://lh3.googleusercontent.com/-PO4E-xZKAnQ/URqvGRqjYkI/AAAAAAAAAbs/42nyADFsXag/s160-c/The%252520Fisherman.jpg",  
 "https://lh4.googleusercontent.com/-iLyZlzfdy7s/URqvG0YScdI/AAAAAAAAAbs/1J9eDKmkXtk/s160-c/The%252520Night%252520is%252520Coming.jpg",  
 "https://lh6.googleusercontent.com/-G-k7YkkUco0/URqvHhah6fI/AAAAAAAAAbs/_taQQG7t0vo/s160-c/The%252520Road.jpg",  
 "https://lh6.googleusercontent.com/-h-ALJt7kSus/URqvIThqYfI/AAAAAAAAAbs/ejiv35olWS8/s160-c/Tokyo%252520Heights.jpg",  
 "https://lh5.googleusercontent.com/-Hy9k-TbS7xg/URqvIjQMOxI/AAAAAAAAAbs/RSpmmOATSkg/s160-c/Tokyo%252520Highway.jpg",  
 "https://lh6.googleusercontent.com/-83oOvMb4OZs/URqvJL0T7lI/AAAAAAAAAbs/c5TECZ6RONM/s160-c/Tokyo%252520Smog.jpg",  
 "https://lh3.googleusercontent.com/-FB-jfgREEfI/URqvJI3EXAI/AAAAAAAAAbs/XfyweiRF4v8/s160-c/Tufa%252520at%252520Night.jpg",  
 "https://lh4.googleusercontent.com/-vngKD5Z1U8w/URqvJUCEgPI/AAAAAAAAAbs/ulxCMVcU6EU/s160-c/Valley%252520Sunset.jpg",  
 "https://lh6.googleusercontent.com/-DOz5I2E2oMQ/URqvKMND1kI/AAAAAAAAAbs/Iqf0IsInleo/s160-c/Windmill%252520Sunrise.jpg",  
 "https://lh5.googleusercontent.com/-biyiyWcJ9MU/URqvKculiAI/AAAAAAAAAbs/jyPsCplJOpE/s160-c/Windmill.jpg",  
 "https://lh4.googleusercontent.com/-PDT167_xRdA/URqvK36mLcI/AAAAAAAAAbs/oi2ik9QseMI/s160-c/Windmills.jpg",  
 "https://lh5.googleusercontent.com/-kI_QdYx7VlU/URqvLXCB6gI/AAAAAAAAAbs/N31vlZ6u89o/s160-c/Yet%252520Another%252520Rockaway%252520Sunset.jpg",  
 "https://lh4.googleusercontent.com/-e9NHZ5k5MSs/URqvMIBZjtI/AAAAAAAAAbs/1fV810rDNfQ/s160-c/Yosemite%252520Tree.jpg", };  
 
}<span style="font-family:Times New Roman;font-size:14px;">  
</span>  

package com.example.asyncimageloader;  
 
import java.io.IOException;  
import java.net.HttpURLConnection;  
import java.net.URL;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
 
import android.content.Context;  
import android.graphics.Bitmap;  
import android.graphics.BitmapFactory;  
import android.os.Handler;  
import android.os.Message;  
import android.support.v4.util.LruCache;  
 
public class ImageDownLoader {  
 /** 
     * 缓存Image的类，当存储Image的大小大于LruCache设定的值，系统自动释放内存 
     */ 
 private LruCache<String, Bitmap> mMemoryCache;  
 /** 
     * 操作文件相关类对象的引用 
     */ 
 private FileUtils fileUtils;  
 /** 
     * 下载Image的线程池 
     */ 
 private ExecutorService mImageThreadPool = null;  
 
 
 public ImageDownLoader(Context context){  
 //获取系统分配给每个应用程序的最大内存，每个应用系统分配32M 
 int maxMemory = (int) Runtime.getRuntime().maxMemory();    
 int mCacheSize = maxMemory / 8;  
 //给LruCache分配1/8 4M 
        mMemoryCache = new LruCache<String, Bitmap>(mCacheSize){  
 
 //必须重写此方法，来测量Bitmap的大小 
 @Override 
 protected int sizeOf(String key, Bitmap value) {  
 return value.getRowBytes() * value.getHeight();  
            }  
 
        };  
 
        fileUtils = new FileUtils(context);  
    }  
 
 
 /** 
     * 获取线程池的方法，因为涉及到并发的问题，我们加上同步锁 
     * @return 
     */ 
 public ExecutorService getThreadPool(){  
 if(mImageThreadPool == null){  
 synchronized(ExecutorService.class){  
 if(mImageThreadPool == null){  
 //为了下载图片更加的流畅，我们用了2个线程来下载图片 
                    mImageThreadPool = Executors.newFixedThreadPool(2);  
                }  
            }  
        }  
 
 return mImageThreadPool;  
 
    }  
 
 /** 
     * 添加Bitmap到内存缓存 
     * @param key 
     * @param bitmap 
     */ 
 public void addBitmapToMemoryCache(String key, Bitmap bitmap) {    
 if (getBitmapFromMemCache(key) == null && bitmap != null) {    
            mMemoryCache.put(key, bitmap);    
        }    
    }    
 
 /** 
     * 从内存缓存中获取一个Bitmap 
     * @param key 
     * @return 
     */ 
 public Bitmap getBitmapFromMemCache(String key) {    
 return mMemoryCache.get(key);    
    }   
 
 /** 
     * 先从内存缓存中获取Bitmap,如果没有就从SD卡或者手机缓存中获取，SD卡或者手机缓存 
     * 没有就去下载 
     * @param url 
     * @param listener 
     * @return 
     */ 
 public Bitmap downloadImage(final String url, final onImageLoaderListener listener){  
 //替换Url中非字母和非数字的字符，这里比较重要，因为我们用Url作为文件名，比如我们的Url 
 //是Http://xiaanming/abc.jpg;用这个作为图片名称，系统会认为xiaanming为一个目录， 
 //我们没有创建此目录保存文件就会报错 
 final String subUrl = url.replaceAll("[^\\w]", "");  
        Bitmap bitmap = showCacheBitmap(subUrl);  
 if(bitmap != null){  
 return bitmap;  
        }else{  
 
 final Handler handler = new Handler(){  
 @Override 
 public void handleMessage(Message msg) {  
 super.handleMessage(msg);  
                    listener.onImageLoader((Bitmap)msg.obj, url);  
                }  
            };  
 
            getThreadPool().execute(new Runnable() {  
 
 @Override 
 public void run() {  
                    Bitmap bitmap = getBitmapFormUrl(url);  
                    Message msg = handler.obtainMessage();  
                    msg.obj = bitmap;  
                    handler.sendMessage(msg);  
 
 try {  
 //保存在SD卡或者手机目录 
                        fileUtils.savaBitmap(subUrl, bitmap);  
                    } catch (IOException e) {  
                        e.printStackTrace();  
                    }  
 
 //将Bitmap 加入内存缓存 
                    addBitmapToMemoryCache(subUrl, bitmap);  
                }  
            });  
        }  
 
 return null;  
    }  
 
 /** 
     * 获取Bitmap, 内存中没有就去手机或者sd卡中获取，这一步在getView中会调用，比较关键的一步 
     * @param url 
     * @return 
     */ 
 public Bitmap showCacheBitmap(String url){  
 if(getBitmapFromMemCache(url) != null){  
 return getBitmapFromMemCache(url);  
        }else if(fileUtils.isFileExists(url) && fileUtils.getFileSize(url) != 0){  
 //从SD卡获取手机里面获取Bitmap 
            Bitmap bitmap = fileUtils.getBitmap(url);  
 
 //将Bitmap 加入内存缓存 
            addBitmapToMemoryCache(url, bitmap);  
 return bitmap;  
        }  
 
 return null;  
    }  
 
 
 /** 
     * 从Url中获取Bitmap 
     * @param url 
     * @return 
     */ 
 private Bitmap getBitmapFormUrl(String url) {  
        Bitmap bitmap = null;  
        HttpURLConnection con = null;  
 try {  
            URL mImageUrl = new URL(url);  
            con = (HttpURLConnection) mImageUrl.openConnection();  
            con.setConnectTimeout(10 * 1000);  
            con.setReadTimeout(10 * 1000);  
            con.setDoInput(true);  
            con.setDoOutput(true);  
            bitmap = BitmapFactory.decodeStream(con.getInputStream());  
        } catch (Exception e) {  
            e.printStackTrace();  
        } finally {  
 if (con != null) {  
                con.disconnect();  
            }  
        }  
 return bitmap;  
    }  
 
 /** 
     * 取消正在下载的任务 
     */ 
 public synchronized void cancelTask() {  
 if(mImageThreadPool != null){  
            mImageThreadPool.shutdownNow();  
            mImageThreadPool = null;  
        }  
    }  
 
 
 /** 
     * 异步下载图片的回调接口 
     * @author len 
     * 
     */ 
 public interface onImageLoaderListener{  
 void onImageLoader(Bitmap bitmap, String url);  
    }  
 
}  

package com.example.asyncimageloader;  
 
import android.content.Context;  
import android.graphics.Bitmap;  
import android.view.View;  
import android.view.ViewGroup;  
import android.widget.AbsListView;  
import android.widget.AbsListView.OnScrollListener;  
import android.widget.BaseAdapter;  
import android.widget.GridView;  
import android.widget.ImageView;  
 
import com.example.asyncimageloader.ImageDownLoader.onImageLoaderListener;  
 
public class ImageAdapter extends BaseAdapter implements OnScrollListener{  
 /** 
     * 上下文对象的引用 
     */ 
 private Context context;  
 
 /** 
     * Image Url的数组 
     */ 
 private String [] imageThumbUrls;  
 
 /** 
     * GridView对象的应用 
     */ 
 private GridView mGridView;  
 
 /** 
     * Image 下载器 
     */ 
 private ImageDownLoader mImageDownLoader;  
 
 /** 
     * 记录是否刚打开程序，用于解决进入程序不滚动屏幕，不会下载图片的问题。 
     * 参考http://blog.csdn.net/guolin_blog/article/details/9526203#comments 
     */ 
 private boolean isFirstEnter = true;  
 
 /** 
     * 一屏中第一个item的位置 
     */ 
 private int mFirstVisibleItem;  
 
 /** 
     * 一屏中所有item的个数 
     */ 
 private int mVisibleItemCount;  
 
 
 public ImageAdapter(Context context, GridView mGridView, String [] imageThumbUrls){  
 this.context = context;  
 this.mGridView = mGridView;  
 this.imageThumbUrls = imageThumbUrls;  
        mImageDownLoader = new ImageDownLoader(context);  
        mGridView.setOnScrollListener(this);  
    }  
 
 @Override 
 public void onScrollStateChanged(AbsListView view, int scrollState) {  
 //仅当GridView静止时才去下载图片，GridView滑动时取消所有正在下载的任务   
 if(scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE){  
            showImage(mFirstVisibleItem, mVisibleItemCount);  
        }else{  
            cancelTask();  
        }  
 
    }  
 
 
 /** 
     * GridView滚动的时候调用的方法，刚开始显示GridView也会调用此方法 
     */ 
 @Override 
 public void onScroll(AbsListView view, int firstVisibleItem,  
 int visibleItemCount, int totalItemCount) {  
        mFirstVisibleItem = firstVisibleItem;  
        mVisibleItemCount = visibleItemCount;  
 // 因此在这里为首次进入程序开启下载任务。  
 if(isFirstEnter && visibleItemCount > 0){  
            showImage(mFirstVisibleItem, mVisibleItemCount);  
            isFirstEnter = false;  
        }  
    }  
 
 
 @Override 
 public int getCount() {  
 return imageThumbUrls.length;  
    }  
 
 @Override 
 public Object getItem(int position) {  
 return imageThumbUrls[position];  
    }  
 
 @Override 
 public long getItemId(int position) {  
 return position;  
    }  
 
 @Override 
 public View getView(int position, View convertView, ViewGroup parent) {  
        ImageView mImageView;  
 final String mImageUrl = imageThumbUrls[position];  
 if(convertView == null){  
            mImageView = new ImageView(context);  
        }else{  
            mImageView = (ImageView) convertView;  
        }  
 
        mImageView.setLayoutParams(new GridView.LayoutParams(150, 150));  
        mImageView.setScaleType(ImageView.ScaleType.CENTER_INSIDE);  
 
 //给ImageView设置Tag,这里已经是司空见惯了 
        mImageView.setTag(mImageUrl);  
 
 
 /*******************************去掉下面这几行试试是什么效果****************************/ 
        Bitmap bitmap = mImageDownLoader.showCacheBitmap(mImageUrl.replaceAll("[^\\w]", ""));  
 if(bitmap != null){  
            mImageView.setImageBitmap(bitmap);  
        }else{  
            mImageView.setImageDrawable(context.getResources().getDrawable(R.drawable.ic_empty));  
        }  
 /**********************************************************************************/ 
 
 
 return mImageView;  
    }  
 
 /** 
     * 显示当前屏幕的图片，先会去查找LruCache，LruCache没有就去sd卡或者手机目录查找，在没有就开启线程去下载 
     * @param firstVisibleItem 
     * @param visibleItemCount 
     */ 
 private void showImage(int firstVisibleItem, int visibleItemCount){  
        Bitmap bitmap = null;  
 for(int i=firstVisibleItem; i<firstVisibleItem + visibleItemCount; i++){  
            String mImageUrl = imageThumbUrls[i];  
 final ImageView mImageView = (ImageView) mGridView.findViewWithTag(mImageUrl);  
            bitmap = mImageDownLoader.downloadImage(mImageUrl, new onImageLoaderListener() {  
 
 @Override 
 public void onImageLoader(Bitmap bitmap, String url) {  
 if(mImageView != null && bitmap != null){  
                        mImageView.setImageBitmap(bitmap);  
                    }  
 
                }  
            });  
 
 //if(bitmap != null){ 
 //  mImageView.setImageBitmap(bitmap); 
 //}else{ 
 //  mImageView.setImageDrawable(context.getResources().getDrawable(R.drawable.ic_empty)); 
 //} 
        }  
    }  
 
 /** 
     * 取消下载任务 
     */ 
 public void cancelTask(){  
        mImageDownLoader.cancelTask();  
    }  
 
 
}  

package com.example.asyncimageloader;  
 
import android.app.Activity;  
import android.os.Bundle;  
import android.view.Menu;  
import android.view.MenuItem;  
import android.widget.GridView;  
import android.widget.Toast;  
 
public class MainActivity extends Activity {  
 private GridView mGridView;  
 private String [] imageThumbUrls = Images.imageThumbUrls;   
 private ImageAdapter mImageAdapter;  
 private FileUtils fileUtils;  
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) {  
 super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        fileUtils = new FileUtils(this);  
        mGridView = (GridView) findViewById(R.id.gridView);  
        mImageAdapter = new ImageAdapter(this, mGridView, imageThumbUrls);  
        mGridView.setAdapter(mImageAdapter);  
    }  
 
 @Override 
 protected void onDestroy() {  
        mImageAdapter.cancelTask();  
 super.onDestroy();  
    }  
 
 @Override 
 public boolean onCreateOptionsMenu(Menu menu) {  
 super.onCreateOptionsMenu(menu);  
        menu.add("删除手机中图片缓存");  
 return super.onCreateOptionsMenu(menu);  
    }  
 
 @Override 
 public boolean onOptionsItemSelected(MenuItem item) {  
 switch (item.getItemId()) {  
 case 0:  
            fileUtils.deleteFile();  
            Toast.makeText(getApplication(), "清空缓存成功", Toast.LENGTH_SHORT).show();  
 break;  
        }  
 return super.onOptionsItemSelected(item);  
    }  
 
}<span style="font-family:Times New Roman;font-size:14px;">  
</span>  

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 xmlns:tools="http://schemas.android.com/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 tools:context=".MainActivity" > 
 
 <GridView 
 android:id="@+id/gridView" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 android:stretchMode="columnWidth" 
 android:columnWidth="90dip" 
 android:verticalSpacing="10dip" 
 android:horizontalSpacing="10dip" 
 android:cacheColorHint="@android:color/transparent" 
 android:numColumns="auto_fit" > 
 </GridView> 
 
</RelativeLayout> 

<uses-permission android:name="android.permission.INTERNET" /> 
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />