Android之ListView优化(使用Lrucache，图片滑动时使用默认图片，停止时加载)

注意：LruCache是有版本限制的，低版本的sdk需要在libs文件夹添加相应的support-4v文件。
本文改造的大部分是参考http://www.iteye.com/topic/1118828，感谢。
不废话直接上工程代码，内有关键注释，项目就不上传了，自己对照着上面网址改呗。

首先是Application文件，负责创建图片存储文件夹：

public class MyApp extends Application{    @Override    public void onCreate() {        super.onCreate();        File f = new File(Environment.getExternalStorageDirectory()+"/TestSyncListView/pic/");        if (!f.exists()) {            f.mkdirs();        }    }}

图像读取工具类：

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public class SyncImageLoaderUtil {

    privateObject lock = newObject(); 

       

    privateboolean mAllowLoad = true; 

   

    privateboolean firstLoad = true; 

   

    privateint mStartLoadLimit = 0; 

   

    privateint mStopLoadLimit = 0; 

   

    finalHandler handler = newHandler(); 

   

//    private HashMap<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>(); 

   

    privateLruCache<String,Bitmap> mMemoryCache;

     

    RunInOtherThread runInOutherThread; 

   

    publicSyncImageLoaderUtil(Context context) { 

        super(); 

         

        intmemClass = ((ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();

        intcacheSize = 1024 * 1024 *memClass /8;

        mMemoryCache =new LruCache<String, Bitmap>(cacheSize){

            @Override

            protectedint sizeOf(String key, Bitmap value) {

                // TODO Auto-generated method stub

                returnvalue.getRowBytes();

            }

        };

         

        runInOutherThread =new RunInOtherThread(); 

        runInOutherThread.start(); 

    } 

   

    publicinterface OnImageLoadListener { 

        publicvoid onImageLoad(Integer t, Drawable drawable); 

   

        publicvoid onError(Integer t); 

    } 

   

    publicvoid setLoadLimit(intstartLoadLimit, intstopLoadLimit) { 

        if(startLoadLimit > stopLoadLimit) { 

//          LogUtil.i("test", startLoadLimit+"--错误---"+stopLoadLimit);

            return; 

        } 

        mStartLoadLimit = startLoadLimit; 

        mStopLoadLimit = stopLoadLimit; 

    } 

   

    publicvoid restore() { 

        mAllowLoad =true; 

        firstLoad =true; 

    } 

   

    publicvoid lock() { 

        mAllowLoad =false; 

        firstLoad =false; 

    } 

   

    publicvoid unlock() { 

        mAllowLoad =true; 

        synchronized(lock) { 

            lock.notifyAll(); 

        } 

    } 

   

    publicvoid loadImage(Integer t, String imageUrl, 

            OnImageLoadListener listener) { 

        finalOnImageLoadListener mListener = listener; 

        finalString mImageUrl = imageUrl; 

        finalInteger mt = t; 

           

        runInOutherThread.getHandler().post(newRunnable() { 

   

            @Override 

            publicvoid run() { 

                if(!mAllowLoad) { 

                    synchronized(lock) { 

                        try{ 

                            lock.wait(); 

                        }catch (InterruptedException e) { 

                            // TODO Auto-generated catch block 

                            e.printStackTrace(); 

                        } 

                    } 

                } 

                   

                if(mAllowLoad && firstLoad) { 

                    loadImage(mImageUrl, mt, mListener); 

                } 

   

//                LogUtil.e("test", "原始开始："+mStartLoadLimit+"原始当前位置："+mt+"原始结束："+mStopLoadLimit);

                if(mAllowLoad && mt <= mStopLoadLimit && mt >= mStartLoadLimit) { 

//                  LogUtil.e("test", "开始："+mStartLoadLimit+"当前位置："+mt+"结束："+mStopLoadLimit);

                    loadImage(mImageUrl, mt, mListener);

                } 

            } 

   

        }); 

    } 

       

    privatevoid loadImage(finalString mImageUrl, finalInteger mt, 

            finalOnImageLoadListener mListener) { 

   

        if(mImageUrl!=null&& mMemoryCache.get(mImageUrl)!=null) { 

//            SoftReference<Drawable> softReference = imageCache.get(mImageUrl); 

            finalDrawable d = newBitmapDrawable(mMemoryCache.get(mImageUrl)); 

//            LogUtil.d("ppp", "drawable:"+d);

            if(d != null) { 

                handler.post(newRunnable() { 

                    @Override 

                    publicvoid run() { 

                        if(mAllowLoad) { 

                            mListener.onImageLoad(mt, d); 

                        } 

                    } 

                }); 

                return; 

            } 

        } 

        try{ 

            finalDrawable d = loadImageFromUrl(mImageUrl); 

            if(d != null) { 

                mMemoryCache.put(mImageUrl, ((BitmapDrawable)d).getBitmap());

            } 

            handler.post(newRunnable() { 

                @Override 

                publicvoid run() { 

                    if(mAllowLoad) { 

                        mListener.onImageLoad(mt, d); 

                    } 

                } 

            }); 

        }catch (IOException e) { 

            handler.post(newRunnable() { 

                @Override 

                publicvoid run() { 

                    mListener.onError(mt); 

                } 

            }); 

            e.printStackTrace(); 

        } 

    } 

   

    publicstatic Drawable loadImageFromUrl(String url)throws IOException { 

        //DebugUtil.debug(url); 

        if(Environment.getExternalStorageState().equals( 

                Environment.MEDIA_MOUNTED)) { 

            File f =new File(Environment.getExternalStorageDirectory() 

                    +"/Weiyu/pic/" + MD5Util.getMD5(url.getBytes())); 

            if(f.exists()) { 

                FileInputStream fis =new FileInputStream(f); 

                Drawable d = Drawable.createFromStream(fis,"src"); 

                returnd; 

            } 

            URL m =new URL(url); 

            InputStream i = (InputStream) m.getContent(); 

            DataInputStream in =new DataInputStream(i); 

            FileOutputStream out =new FileOutputStream(f); 

            byte[] buffer =new byte[1024]; 

            intbyteread = 0; 

            while((byteread = in.read(buffer)) != -1) { 

                out.write(buffer,0, byteread); 

            } 

            

            in.close(); 

            out.close();

            returnloadImageFromUrl(url); 

        }else { 

            URL m =new URL(url); 

            InputStream i = (InputStream) m.getContent(); 

            Drawable d = Drawable.createFromStream(i,"src"); 

            returnd; 

        } 

   

    } 

}

　　
线程辅助类：

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public class RunInOtherThread {

    privatestatic final String LOG_TAG = "RunInOtherThread"; 

     

    privateLooperThread localThread = newLooperThread(); 

       

    privateboolean isRunning = true; 

   

    publicHandler getHandler(){ 

        returnlocalThread.getHandler(); 

    } 

       

    privateclass LooperThread extends Thread { 

        privateHandler mHandler; 

   

        publicvoid run() { 

            Looper.prepare(); 

            mHandler =new Handler() { 

                publicvoid handleMessage(Message msg) { 

                    onReceiveMessage(msg.what); 

                } 

            }; 

            Looper.loop(); 

        } 

           

        Handler getHandler(){ 

            returnmHandler; 

        } 

      

    } 

       

    publicvoid start(){ 

        localThread.start(); 

    } 

       

    publicvoid quit(){ 

        localThread.getHandler().getLooper().quit(); 

    } 

       

    publicvoid sendMessage(intwhat){ 

        getHandler().sendEmptyMessage(what); 

    } 

       

    publicThread getThread(){ 

        returnlocalThread; 

    } 

       

    publicvoid onReceiveMessage(intwhat){};

}

　　
使用类：

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// 实例化工具类

SyncImageLoaderUtil syncImageLoader =new SyncImageLoaderUtil(mContext);

 

syncImageLoader.loadImage(position, model.mPic, imageLoadListener);//应用接口：参数一是加载图片的位置；参数二是加载的ImageView；参数三是回调接口

 

// map保存的键是位置，值是listview对应位置的布局

HashMap map = new HashMap();

map.put(position, convertView);

 

SyncImageLoaderUtil.OnImageLoadListener imageLoadListener =new SyncImageLoaderUtil.OnImageLoadListener() {

 

        @Override

        publicvoid onImageLoad(Integer t, Drawable drawable) {

            View view = (View) map.get(t);

            if(view != null) {

                ImageView iv = (ImageView) view.findViewById(R.id.image);

                iv.setBackgroundDrawable(drawable);

            }

        }

 

        @Override

        publicvoid onError(Integer t) {

                        // 图片加载失败

                       // 取得listview对应的位置的行的内容布局

                    MusicModel model = (MusicModel) getItem(t);

            View view = mListView.findViewWithTag(model);

            if(view != null) {

                ImageView iv = (ImageView) view.findViewById(R.id.image);

                iv.setBackgroundResource(R.drawable.img_pic);

            }

        }

 

    };

 

 

// 实现类而且需要实现OnScrollListener接口

public void loadImage() {

                // 不要在这里使用listview的getFirstVisiblePosition方法，位置不准

        if(end >= getCount()) {

            end = getCount() -1;

        }

        syncImageLoader.setLoadLimit(start, end);

        syncImageLoader.unlock();

    }

 

    @Override

    publicvoid onScrollStateChanged(AbsListView view,int scrollState) {

        // TODO Auto-generated method stub

        if(lodingView) {

            switch(scrollState) {

            caseAbsListView.OnScrollListener.SCROLL_STATE_FLING:

                syncImageLoader.lock();

                break;

            caseAbsListView.OnScrollListener.SCROLL_STATE_IDLE:

 

                loadImage();

                break;

            caseAbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:

                syncImageLoader.lock();

                break;

            default:

                break;

            }

        }

    }

 

    @Override

    publicvoid onScroll(AbsListView view,int firstVisibleItem,

            intvisibleItemCount, inttotalItemCount) {

        // 在这里取得的位置较准确，不过也会出现特殊的奇疤机型是不行的

                // start与end是定义的变量

        start = firstVisibleItem;

        end = firstVisibleItem + visibleItemCount;

        if(firstVisibleItem != 0) {

                        // lodingView是控制变量，用来控制第一次进来视图加载读取图片

            lodingView =true;

        }else {

            lodingView =false;

            loadImage();

        }

    }