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：
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：
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：
// 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();
}
}
