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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publicclassSyncImageLoaderUtil {

privateObject lock = newObject();

privatebooleanmAllowLoad = true;

privatebooleanfirstLoad = true;

privateintmStartLoadLimit = 0;

privateintmStopLoadLimit = 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 = newLruCache<String, Bitmap>(cacheSize){

@Override

protectedintsizeOf(String key, Bitmap value) {

// TODO Auto-generated method stub

returnvalue.getRowBytes();

}

};

runInOutherThread = newRunInOtherThread();

runInOutherThread.start();

}

publicinterfaceOnImageLoadListener {

publicvoidonImageLoad(Integer t, Drawable drawable);

publicvoidonError(Integer t);

}

publicvoidsetLoadLimit(intstartLoadLimit, intstopLoadLimit) {

if(startLoadLimit > stopLoadLimit) {

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

return;

}

mStartLoadLimit = startLoadLimit;

mStopLoadLimit = stopLoadLimit;

}

publicvoidrestore() {

mAllowLoad = true;

firstLoad = true;

}

publicvoidlock() {

mAllowLoad = false;

firstLoad = false;

}

publicvoidunlock() {

mAllowLoad = true;

synchronized(lock) {

lock.notifyAll();

}

}

publicvoidloadImage(Integer t, String imageUrl,

OnImageLoadListener listener) {

finalOnImageLoadListener mListener = listener;

finalString mImageUrl = imageUrl;

finalInteger mt = t;

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

@Override

publicvoidrun() {

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);

}

}

});

}

privatevoidloadImage(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

publicvoidrun() {

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

publicvoidrun() {

if(mAllowLoad) {

mListener.onImageLoad(mt, d);

}

}

});

} catch(IOException e) {

handler.post(newRunnable() {

@Override

publicvoidrun() {

mListener.onError(mt);

}

});

e.printStackTrace();

}

}

publicstaticDrawable loadImageFromUrl(String url) throwsIOException {

//DebugUtil.debug(url);

if(Environment.getExternalStorageState().equals(

Environment.MEDIA_MOUNTED)) {

File f = newFile(Environment.getExternalStorageDirectory()

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

if(f.exists()) {

FileInputStream fis = newFileInputStream(f);

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

returnd;

}

URL m = newURL(url);

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

DataInputStream in = newDataInputStream(i);

FileOutputStream out = newFileOutputStream(f);

byte[] buffer = newbyte[1024];

intbyteread = 0;

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

out.write(buffer, 0, byteread);

}

in.close();

out.close();

returnloadImageFromUrl(url);

} else{

URL m = newURL(url);

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

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

returnd;

}

}

}

　　
线程辅助类：

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publicclassRunInOtherThread {

privatestaticfinalString LOG_TAG = "RunInOtherThread";

privateLooperThread localThread = newLooperThread();

privatebooleanisRunning = true;

publicHandler getHandler(){

returnlocalThread.getHandler();

}

privateclassLooperThread extendsThread {

privateHandler mHandler;

publicvoidrun() {

Looper.prepare();

mHandler = newHandler() {

publicvoidhandleMessage(Message msg) {

onReceiveMessage(msg.what);

}

};

Looper.loop();

}

Handler getHandler(){

returnmHandler;

}

}

publicvoidstart(){

localThread.start();

}

publicvoidquit(){

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

}

publicvoidsendMessage(intwhat){

getHandler().sendEmptyMessage(what);

}

publicThread getThread(){

returnlocalThread;

}

publicvoidonReceiveMessage(intwhat){};

}

　　
使用类：

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// 实例化工具类

SyncImageLoaderUtil syncImageLoader = newSyncImageLoaderUtil(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 = newHashMap();

map.put(position, convertView);

SyncImageLoaderUtil.OnImageLoadListener imageLoadListener = newSyncImageLoaderUtil.OnImageLoadListener() {

@Override

publicvoidonImageLoad(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

publicvoidonError(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

publicvoidloadImage() {

// 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

publicvoidonScrollStateChanged(AbsListView view, intscrollState) {

// 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

publicvoidonScroll(AbsListView view, intfirstVisibleItem,

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();

}

}