<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <ListView

        android:id="@+id/mylist"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:divider="#b5b5b5"

        android:dividerHeight="1dp"

        android:listSelector="@drawable/list_selector" />

    <Button

        android:id="@+id/btn_clear"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:text="清除缓存, 重新加载" />

</LinearLayout>

package com.example.androidhive;

import org.json.JSONArray;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.widget.ListView;

public class CustomizedListView extends Activity {

    String url = "http://files.cnblogs.com/liuning8023/Android_Music_Demo_json_array.xml";

    ListView list;

    LazyAdapter adapter;

    /* Button btn; */

    private Handler handler = new Handler() {

        @Override

        public void handleMessage(Message msg) {

            if (msg.what == 0x123) {

                Request rq = new Request();

                JSONArray jsonArr = rq.getJsonFromUrl(url);

                list = (ListView) findViewById(R.id.mylist);

                adapter = new LazyAdapter(CustomizedListView.this, this,

                        jsonArr);

                list.setAdapter(adapter);

                /*

                 * btn = (Button) findViewById(R.id.btn_clear);

                 * btn.setOnClickListener(new OnClickListener() {

                 * 

                 * @Override public void onClick(View arg0) {

                 * adapter.imageLoader.clearCache();

                 * adapter.notifyDataSetChanged(); } });

                 */

            }

            super.handleMessage(msg);

        }

    };

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        new Thread(new Runnable() {

            @Override

            public void run() {

                Message msg = new Message();

                msg.what = 0x123;

                handler.sendMessage(msg);

            }

        }).start();

    }

}

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:background="@drawable/list_selector"

    android:orientation="horizontal"

    android:padding="5dip" >

    <!--  ListRow Left sied Thumbnail image -->

    <LinearLayout android:id="@+id/thumbnail" 

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:padding="3dip"        

        android:layout_alignParentLeft="true"

        android:background="@drawable/image_bg" 

        android:layout_marginRight="5dip">

        <ImageView     

            android:id="@+id/list_image"   

            android:layout_width="50dip"

            android:layout_height="50dip"

            android:src="@drawable/rihanna"/>

    </LinearLayout>

    <!-- Title Of Song-->

    <TextView

        android:id="@+id/title"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignTop="@+id/thumbnail"

        android:layout_toRightOf="@+id/thumbnail"

        android:text="Rihanna Love the way lie"

        android:textColor="#040404"

        android:typeface="sans" 

        android:textSize="15dip"

        android:textStyle="bold"/>

    <!-- Artist Name -->

    <TextView

        android:id="@+id/artist"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:layout_below="@id/title"

        android:textColor="#343434"

        android:textSize="10dip"

        android:layout_marginTop="1dip"

        android:layout_toRightOf="@+id/thumbnail"

        android:text="Just gona stand there and ..." />

    <!-- Rightend Duration -->

    <TextView

        android:id="@+id/duration"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentRight="true"

        android:layout_alignTop="@id/title"

        android:gravity="right"

        android:text="5:45"

        android:layout_marginRight="5dip"

        android:textSize="10dip"

        android:textColor="#10bcc9"

        android:textStyle="bold"/>

     <!-- Rightend Arrow -->    

     <ImageView android:layout_width="wrap_content"

         android:layout_height="wrap_content"

         android:src="@drawable/arrow"

         android:layout_alignParentRight="true"

         android:layout_centerVertical="true"/>

</RelativeLayout>

package com.example.androidhive;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import android.app.Activity;

import android.content.Context;

import android.os.Handler;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.ImageView;

import android.widget.TextView;

public class LazyAdapter extends BaseAdapter {

    private Activity activity;

    private JSONArray data;

    private static LayoutInflater inflater = null;

    public ImageLoader imageLoader;

    public LazyAdapter(Activity a, Handler handler, JSONArray jsonArr) {

        activity = a;

        data = http://www.mamicode.com/jsonArr;

        inflater = (LayoutInflater) activity

                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        imageLoader = new ImageLoader(activity.getApplicationContext());

    }

    public int getCount() {

        return data =http://www.mamicode.com/= null ? 0 : data.length();

    }

    public Object getItem(int position) {

        return position;

    }

    public long getItemId(int position) {

        return position;

    }

    public View getView(int position, View convertView, ViewGroup parent) {

        View vi = convertView;

        if (convertView == null)

            vi = inflater.inflate(R.layout.list_row, null);

        JSONObject song = null;

        ImageView image = (ImageView) vi.findViewById(R.id.list_image);

        TextView tvartist = (TextView) vi.findViewById(R.id.artist);

        TextView tvtitle = (TextView) vi.findViewById(R.id.title);

        TextView tvduration = (TextView) vi.findViewById(R.id.duration);

        try {

            song = data.getJSONObject(position);

            imageLoader.DisplayImage(song.getString("thumb_url"), image);

            tvartist.setText(song.getString("artist"));

            tvtitle.setText(song.getString("title"));

            tvduration.setText(song.getString("duration"));

        } catch (JSONException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        return vi;

    }

}

package com.example.androidhive;

import java.io.File;

import android.content.Context;

public class FileCache {

    private File cacheDir;

    public FileCache(Context context) {

        // Find the dir to save cached images

        if (android.os.Environment.getExternalStorageState().equals(

                android.os.Environment.MEDIA_MOUNTED))

            cacheDir = new File(

                    android.os.Environment.getExternalStorageDirectory(),

                    "LazyList");

        else

            cacheDir = context.getCacheDir();

        if (!cacheDir.exists())

            cacheDir.mkdirs();

    }

    public File getFile(String url) {

        // I identify images by hashcode. Not a perfect solution, good for the

        // demo.

        String filename = String.valueOf(url.hashCode());

        // Another possible solution (thanks to grantland)

        // String filename = URLEncoder.encode(url);

        File f = new File(cacheDir, filename);

        return f;

    }

    public void clear() {

        File[] files = cacheDir.listFiles();

        if (files == null)

            return;

        for (File f : files)

            f.delete();

    }

}

package com.example.androidhive;

import java.util.Collections;

import java.util.Iterator;

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.Map.Entry;

import android.graphics.Bitmap;

import android.util.Log;

public class MemoryCache {

    private static final String TAG = "MemoryCache";

    private Map<String, Bitmap> cache=Collections.synchronizedMap(

            new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering

    private long size=0;//current allocated size

    private long limit=1000000;//max memory in bytes

    public MemoryCache(){

        //use 25% of available heap size

        setLimit(Runtime.getRuntime().maxMemory()/4);

    }

    public void setLimit(long new_limit){

        limit=new_limit;

        Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");

    }

    public Bitmap get(String id){

        try{

            if(!cache.containsKey(id))

                return null;

            //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 

            return cache.get(id);

        }catch(NullPointerException ex){

            ex.printStackTrace();

            return null;

        }

    }

    public void put(String id, Bitmap bitmap){

        try{

            if(cache.containsKey(id))

                size-=getSizeInBytes(cache.get(id));

            cache.put(id, bitmap);

            size+=getSizeInBytes(bitmap);

            checkSize();

        }catch(Throwable th){

            th.printStackTrace();

        }

    }

    private void checkSize() {

        Log.i(TAG, "cache size="+size+" length="+cache.size());

        if(size>limit){

            Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();//least recently accessed item will be the first one iterated  

            while(iter.hasNext()){

                Entry<String, Bitmap> entry=iter.next();

                size-=getSizeInBytes(entry.getValue());

                iter.remove();

                if(size<=limit)

                    break;

            }

            Log.i(TAG, "Clean cache. New size "+cache.size());

        }

    }

    public void clear() {

        try{

            //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 

            cache.clear();

            size=0;

        }catch(NullPointerException ex){

            ex.printStackTrace();

        }

    }

    long getSizeInBytes(Bitmap bitmap) {

        if(bitmap==null)

            return 0;

        return bitmap.getRowBytes() * bitmap.getHeight();

    }

}

package com.example.androidhive;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.Collections;

import java.util.Map;

import java.util.WeakHashMap;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import android.os.Handler;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.widget.ImageView;

public class ImageLoader {

    MemoryCache memoryCache = new MemoryCache();

    FileCache fileCache;

    private Map<ImageView, String> imageViews = Collections

            .synchronizedMap(new WeakHashMap<ImageView, String>());

    ExecutorService executorService;

    Handler handler = new Handler();// handler to display images in UI thread

    public ImageLoader(Context context) {

        fileCache = new FileCache(context);

        executorService = Executors.newFixedThreadPool(5);

    }

    final int stub_id = R.drawable.stub;

    /*

     * 显示图片 若缓存存在，则显示，否则获取

     */

    public void DisplayImage(String url, ImageView imageView) {

        imageViews.put(imageView, url);

        Bitmap bitmap = memoryCache.get(url); // 根据 url 从内存获得图片

        if (bitmap != null)

            imageView.setImageBitmap(bitmap);

        else {

            queuePhoto(url, imageView);

            imageView.setImageResource(stub_id);

        }

    }

    private void queuePhoto(String url, ImageView imageView) {

        PhotoToLoad p = new PhotoToLoad(url, imageView);

        executorService.submit(new PhotosLoader(p));

    }

    private Bitmap getBitmap(String url) {

        File f = fileCache.getFile(url);

        // from SD cache

        Bitmap b = decodeFile(f);

        if (b != null)

            return b;

        // from web

        try {

            Bitmap bitmap = null;

            URL imageUrl = new URL(url);

            HttpURLConnection conn = (HttpURLConnection) imageUrl

                    .openConnection();

            conn.setRequestMethod("GET");

            // Sets the flag indicating whether this URLConnection allows input.

            // conn.setDoInput(true);

            conn.setConnectTimeout(3000);

            conn.setReadTimeout(3000);

            // Flag to define whether the protocol will automatically follow

            // redirects or not.

            conn.setInstanceFollowRedirects(true);

            int response_code = conn.getResponseCode();

            if (response_code == 200) {

                InputStream is = conn.getInputStream();

                OutputStream os = new FileOutputStream(f);

                StreamUtils.CopyStream(is, os);

                os.close();

                conn.disconnect();

                bitmap = decodeFile(f);

                return bitmap;

            } else {

                conn.disconnect();

                return null;

            }

        } catch (Throwable ex) {

            ex.printStackTrace();

            if (ex instanceof OutOfMemoryError)

                memoryCache.clear();

            return null;

        }

    }

    // decodes image and scales it to reduce memory consumption

    private Bitmap decodeFile(File f) {

        try {

            // decode image size

            BitmapFactory.Options o = new BitmapFactory.Options();

            o.inJustDecodeBounds = true;

            FileInputStream stream1 = new FileInputStream(f);

            BitmapFactory.decodeStream(stream1, null, o);

            stream1.close();

            // Find the correct scale value. It should be the power of 2.

            final int REQUIRED_SIZE = 70;

            int width_tmp = o.outWidth, height_tmp = o.outHeight;

            int scale = 1;

            while (true) {

                if (width_tmp / 2 < REQUIRED_SIZE

                        || height_tmp / 2 < REQUIRED_SIZE)

                    break;

                width_tmp /= 2;

                height_tmp /= 2;

                scale *= 2;

            }

            // decode with inSampleSize

            BitmapFactory.Options o2 = new BitmapFactory.Options();

            o2.inSampleSize = scale;

            FileInputStream stream2 = new FileInputStream(f);

            Bitmap bitmap = BitmapFactory.decodeStream(stream2, null, o2);

            stream2.close();

            return bitmap;

        } catch (FileNotFoundException e) {

        } catch (IOException e) {

            e.printStackTrace();

        }

        return null;

    }

    // Task for the queue

    private class PhotoToLoad {

        public String url;

        public ImageView imageView;

        public PhotoToLoad(String u, ImageView i) {

            url = u;

            imageView = i;

        }

    }

    class PhotosLoader implements Runnable {

        PhotoToLoad photoToLoad;

        PhotosLoader(PhotoToLoad photoToLoad) {

            this.photoToLoad = photoToLoad;

        }

        @Override

        public void run() {

            try {

                if (imageViewReused(photoToLoad))

                    return;

                Bitmap bmp = getBitmap(photoToLoad.url);

                memoryCache.put(photoToLoad.url, bmp);

                if (imageViewReused(photoToLoad))

                    return;

                BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad);

                handler.post(bd);

            } catch (Throwable th) {

                th.printStackTrace();

            }

        }

    }

    boolean imageViewReused(PhotoToLoad photoToLoad) {

        String tag = imageViews.get(photoToLoad.imageView);

        if (tag == null || !tag.equals(photoToLoad.url))

            return true;

        return false;

    }

    // Used to display bitmap in the UI thread

    class BitmapDisplayer implements Runnable {

        Bitmap bitmap;

        PhotoToLoad photoToLoad;

        public BitmapDisplayer(Bitmap b, PhotoToLoad p) {

            bitmap = b;

            photoToLoad = p;

        }

        public void run() {

            if (imageViewReused(photoToLoad))

                return;

            if (bitmap != null)

                photoToLoad.imageView.setImageBitmap(bitmap);

            else

                photoToLoad.imageView.setImageResource(stub_id);

        }

    }

    public void clearCache() {

        memoryCache.clear();

        fileCache.clear();

    }

}

package com.example.androidhive;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.UnsupportedEncodingException;

import java.net.HttpURLConnection;

import java.net.URL;

import org.json.JSONArray;

import org.json.JSONException;

public class Request {

    public Request() {

    }

    public JSONArray getJsonFromUrl(String urlStr) {

        try {

            URL url = new URL(urlStr);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            conn.setRequestMethod("GET");

            // Sets the flag indicating whether this URLConnection allows input.

            // conn.setDoInput(true);

            conn.setConnectTimeout(3000);

            conn.setReadTimeout(3000);

            // Flag to define whether the protocol will automatically follow

            // redirects or not.

            conn.setInstanceFollowRedirects(true);

            int response_code = conn.getResponseCode();

            if (response_code == 200) {

                InputStream in = conn.getInputStream();

                InputStreamReader inputReader = new InputStreamReader(in);

                BufferedReader buffReader = new BufferedReader(inputReader);

                String line = "", JsonStr = "";

                while ((line = buffReader.readLine()) != null) {

                    JsonStr += line;

                }

                JSONArray jsonArray = new JSONArray(JsonStr);

                return jsonArray;

            } else {

                conn.disconnect();

                return null;

            }

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        } catch (JSONException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        return null;

    }

}

package com.example.androidhive;

import java.io.InputStream;

import java.io.OutputStream;

public class StreamUtils {

    public static void CopyStream(InputStream is, OutputStream os)

    {

        final int buffer_size=1024;

        try

        {

            byte[] bytes=new byte[buffer_size];

            for(;;)

            {

              int count=is.read(bytes, 0, buffer_size);

              if(count==-1)

                  break;

              os.write(bytes, 0, count);

            }

        }

        catch(Exception ex){}

    }

}