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 { private Object lock = new Object(); private boolean mAllowLoad = true ; private boolean firstLoad = true ; private int mStartLoadLimit = 0 ; private int mStopLoadLimit = 0 ; final Handler handler = new Handler(); // private HashMap<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>(); private LruCache<String,Bitmap> mMemoryCache; RunInOtherThread runInOutherThread; public SyncImageLoaderUtil(Context context) { super (); int memClass = ((ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass(); int cacheSize = 1024 * 1024 *memClass / 8 ; mMemoryCache = new LruCache<String, Bitmap>(cacheSize){ @Override protected int sizeOf(String key, Bitmap value) { // TODO Auto-generated method stub return value.getRowBytes(); } }; runInOutherThread = new RunInOtherThread(); runInOutherThread.start(); } public interface OnImageLoadListener { public void onImageLoad(Integer t, Drawable drawable); public void onError(Integer t); } public void setLoadLimit( int startLoadLimit, int stopLoadLimit) { if (startLoadLimit > stopLoadLimit) { // LogUtil.i("test", startLoadLimit+"--错误---"+stopLoadLimit); return ; } mStartLoadLimit = startLoadLimit; mStopLoadLimit = stopLoadLimit; } public void restore() { mAllowLoad = true ; firstLoad = true ; } public void lock() { mAllowLoad = false ; firstLoad = false ; } public void unlock() { mAllowLoad = true ; synchronized (lock) { lock.notifyAll(); } } public void loadImage(Integer t, String imageUrl, OnImageLoadListener listener) { final OnImageLoadListener mListener = listener; final String mImageUrl = imageUrl; final Integer mt = t; runInOutherThread.getHandler().post( new Runnable() { @Override public void 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); } } }); } private void loadImage( final String mImageUrl, final Integer mt, final OnImageLoadListener mListener) { if (mImageUrl!= null && mMemoryCache.get(mImageUrl)!= null ) { // SoftReference<Drawable> softReference = imageCache.get(mImageUrl); final Drawable d = new BitmapDrawable(mMemoryCache.get(mImageUrl)); // LogUtil.d("ppp", "drawable:"+d); if (d != null ) { handler.post( new Runnable() { @Override public void run() { if (mAllowLoad) { mListener.onImageLoad(mt, d); } } }); return ; } } try { final Drawable d = loadImageFromUrl(mImageUrl); if (d != null ) { mMemoryCache.put(mImageUrl, ((BitmapDrawable)d).getBitmap()); } handler.post( new Runnable() { @Override public void run() { if (mAllowLoad) { mListener.onImageLoad(mt, d); } } }); } catch (IOException e) { handler.post( new Runnable() { @Override public void run() { mListener.onError(mt); } }); e.printStackTrace(); } } public static 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" ); return d; } 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 ]; int byteread = 0 ; while ((byteread = in.read(buffer)) != - 1 ) { out.write(buffer, 0 , byteread); } in.close(); out.close(); return loadImageFromUrl(url); } else { URL m = new URL(url); InputStream i = (InputStream) m.getContent(); Drawable d = Drawable.createFromStream(i, "src" ); return d; } } }

　　
线程辅助类：

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public class RunInOtherThread { private static final String LOG_TAG = "RunInOtherThread" ; private LooperThread localThread = new LooperThread(); private boolean isRunning = true ; public Handler getHandler(){ return localThread.getHandler(); } private class LooperThread extends Thread { private Handler mHandler; public void run() { Looper.prepare(); mHandler = new Handler() { public void handleMessage(Message msg) { onReceiveMessage(msg.what); } }; Looper.loop(); } Handler getHandler(){ return mHandler; } } public void start(){ localThread.start(); } public void quit(){ localThread.getHandler().getLooper().quit(); } public void sendMessage( int what){ getHandler().sendEmptyMessage(what); } public Thread getThread(){ return localThread; } public void onReceiveMessage( int what){}; }

　　
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 public void 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 public void 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 public void onScrollStateChanged(AbsListView view, int scrollState) { // TODO Auto-generated method stub if (lodingView) { switch (scrollState) { case AbsListView.OnScrollListener.SCROLL_STATE_FLING: syncImageLoader.lock(); break ; case AbsListView.OnScrollListener.SCROLL_STATE_IDLE: loadImage(); break ; case AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL: syncImageLoader.lock(); break ; default : break ; } } } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // 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(); } }