Android网络图片加载优化
网络图片加载优化
比如使用淘宝浏览产品的时候（大部分应用也是如此），就会发现每次下拉产品目录进行更新的时候，都会出现对应的Item的时候，才开始从网络下载并加载图片。
taobao加载
可以看到宝贝图片下拉刷新的时候，图片加载是实时从网络下载的。即使在Wifi的网络环境下，加载图片也是有比较大的延迟。
假设我们浏览每屏宝贝需要2s的时间（人眼对于淘宝搜索的宝贝其实过滤速度非常快）。如果每一屏页面需要1s才可以完全加载完图片，则如果浏览10屏的宝贝，就会需要30s。如果加载图片几乎不需要时间，则只需要20s。这个节约比例是很大的。如果不是使用wifi而是移动网络，则加载时间可能会更长。这种情况不单单是淘宝，很多带有图片的app都会出现这种图片需要很久加载的情况。
而解决这种问题的思路其实很简单也很直观，那就是在wifi或者用户打开设置的情况下，提前加载一屏的图片，保存在本地硬盘（不是内存）。如果浏览到时则从本地加载。
加载的优化基于上一篇文章：
使用Android-Universal-Image-Loader加载网络图片
http://blog.csdn.net/chen52671/article/details/44680765
使用Android-Universal-Image-Loader是为了简化这个例子，如果你有更好地网络图片下载和内存缓存，硬盘缓存的工具，道理是一样的。
实现思路：
1，判断网络环境是否为WiFi。
2，如果是则开启预缓存，当在Page1时，下载Page2的图片到本地；下拉到paga2时，图片直接从本地读取到内存并显示，同时下载Page3到本地。以此类推
让Android-Universal-Image-Loader只下载
ImageLoader主要使用displayImage来加载某URI的图片到ImageView。还有个方法是loadImage()——用来异步加载图片：其也是通过调用displayImage来操作的，不过传递进去的imageAware（可以当ImageView理解）是一个空实现，当Bitmap加载完毕后，返回一个回调。
但是都没法满足我们的要求：图片流只下载至本地硬盘缓存，但是不解析成Bitmap。更不要提将解析好的Bitmap加载到内存缓存中。
借用一张ImageLoader的displayImage流程图：
display-image-flow-chart
图片来自Android Universal Image Loader 源码分析
为了实现只下载，不加载。需要对Android-Universal-Image-Loader做一下变动（对不住了~~）
1，ImageLoader类添加一个downloadImage方法，和displayImage类似，同样要遵循已有的配置，也要判断是不是在本地硬盘缓存已经有该图片。
2，如果DisplayImageOptions根本就没配置cacheOnDisk，那就对不住了，不下载。
修改如下：
增加一个DownloadTask
package com.nostra13.universalimageloader.core;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.ReentrantLock;
import android.os.Handler;
import android.util.Log;
import com.nostra13.universalimageloader.core.decode.ImageDecoder;
import com.nostra13.universalimageloader.core.download.ImageDownloader;
import com.nostra13.universalimageloader.core.listener.DownloadListener;
import com.nostra13.universalimageloader.utils.IoUtils;
public class DownloadTask implements Runnable, IoUtils.CopyListener {
private String Tag = "DownloadTask";
private final ImageLoaderEngine engine;
private final ImageDownloadInfo imageDownloadInfo;
private final Handler handler;
// Helper references
private final ImageLoaderConfiguration configuration;
private final ImageDownloader downloader;
private final ImageDownloader networkDeniedDownloader;
private final ImageDownloader slowNetworkDownloader;
private final ImageDecoder decoder;
final DownloadListener listener;
final String uri;
final DisplayImageOptions options;
private final boolean syncLoading;
public DownloadTask(ImageLoaderEngine engine,
ImageDownloadInfo imageDownloadInfo, Handler handler) {
this.engine = engine;
this.imageDownloadInfo = imageDownloadInfo;
this.handler = handler;
configuration = engine.configuration;
downloader = configuration.downloader;
networkDeniedDownloader = configuration.networkDeniedDownloader;
slowNetworkDownloader = configuration.slowNetworkDownloader;
decoder = configuration.decoder;
uri = imageDownloadInfo.uri;
listener = imageDownloadInfo.listener;
options = imageDownloadInfo.options;
syncLoading = options.isSyncLoading();
}
@Override
public void run() {
if (waitIfPaused())
return;
ReentrantLock downloadLock = engine.getLockForUri(uri);
if (downloadLock.isLocked()) {
Log.d(Tag, "locked");
}
downloadLock.lock();
try {
File imageFile = configuration.diskCache.get(uri);
if (imageFile != null && imageFile.exists()
&& imageFile.length() > 0) {
return;// 文件存在，不用忙活了
}
if (options.isCacheOnDisk()) {
if(tryCacheImageOnDisk()){
listener.onDownloadComplete(uri);
}
}
checkTaskInterrupted();
} catch (TaskCancelledException e) {
fireCancelEvent();
return;
} finally {
downloadLock.unlock();
}
}
private boolean waitIfPaused() {
AtomicBoolean pause = engine.getPause();
if (pause.get()) {
synchronized (engine.getPauseLock()) {
if (pause.get()) {
try {
engine.getPauseLock().wait();
} catch (InterruptedException e) {
return true;
}
}
}
}
return false;
}
String getLoadingUri() {
return uri;
}
private void checkTaskInterrupted() throws TaskCancelledException {
if (isTaskInterrupted()) {
throw new TaskCancelledException();
}
}
/**
* @return true - if current task was interrupted; false -
* otherwise
*/
private boolean isTaskInterrupted() {
if (Thread.interrupted()) {
Log.d(Tag, "Thread interrupted");
return true;
}
return false;
}
static void runTask(Runnable r, boolean sync, Handler handler,
ImageLoaderEngine engine) {
if (sync) {
r.run();
} else if (handler == null) {
engine.fireCallback(r);
} else {
handler.post(r);
}
}
private void fireCancelEvent() {
if (syncLoading || isTaskInterrupted())
return;
Runnable r = new Runnable() {
@Override
public void run() {
listener.onDownloadCancelled(uri);
}
};
runTask(r, false, handler, engine);
}
private boolean tryCacheImageOnDisk() throws TaskCancelledException {
boolean loaded;
try {
loaded = downloadImage();
// 暂时不resize
} catch (IOException e) {
loaded = false;
}
return loaded;
}
private boolean downloadImage() throws IOException {
InputStream is = getDownloader().getStream(uri,
options.getExtraForDownloader());
if (is == null) {
return false;
} else {
try {
return configuration.diskCache.save(uri, is, this);
} finally {
IoUtils.closeSilently(is);
}
}
}
private ImageDownloader getDownloader() {
ImageDownloader d;
if (engine.isNetworkDenied()) {
d = networkDeniedDownloader;
} else if (engine.isSlowNetwork()) {
d = slowNetworkDownloader;
} else {
d = downloader;
}
return d;
}
class TaskCancelledException extends Exception {
}
@Override
public boolean onBytesCopied(int current, int total) {
// TODO Auto-generated method stub
return true;
}
}
增加一个ImageDownloadInfo
package com.nostra13.universalimageloader.core;
import java.util.concurrent.locks.ReentrantLock;
import com.nostra13.universalimageloader.core.listener.DownloadListener;
public class ImageDownloadInfo {
final String uri;
final DownloadListener listener;
final DisplayImageOptions options;
final ReentrantLock downloadLock;
public ImageDownloadInfo(String uri ,DisplayImageOptions options,DownloadListener listener,
ReentrantLock downloadLock) {
this.uri = uri;
this.listener=listener;
this.options = options;
this.downloadLock = downloadLock;
}
}
增加一个DownloadListener监听器
package com.nostra13.universalimageloader.core.listener;
public interface DownloadListener{
void OnDownloadStart(String imageUri);
void onDownloadFailed(String imageUri);
void onDownloadComplete(String imageUri);
void onDownloadCancelled(String imageUri);
}
ImageLoader修改
/*
*
* @param uri Image URI (i.e. "http://site.com/image.png",
* "file:///mnt/sdcard/image.png")
*
* @param listener 图片下载的监听器
*/
public void downloadImage(String uri, DisplayImageOptions options,
DownloadListener listener) {
checkConfiguration();
if (listener == null) {
listener = new DownloadListener() {
@Override
public void onDownloadFailed(String imageUri) {
}
@Override
public void onDownloadComplete(String imageUri) {
}
@Override
public void onDownloadCancelled(String imageUri) {
}
@Override
public void OnDownloadStart(String imageUri) {
}
};
}
if (options == null) {
options = configuration.defaultDisplayImageOptions;
}
if(!options.isCacheOnDisk()) return;
listener.OnDownloadStart(uri);
if (TextUtils.isEmpty(uri)) {
listener.onDownloadFailed(uri);
return;
}
ImageDownloadInfo imageDownloadInfo = new ImageDownloadInfo(uri,options,listener,engine.getLockForUri(uri));
DownloadTask downloadTask = new DownloadTask(
engine, imageDownloadInfo,defineHandler(options));
if (options.isSyncLoading()) {
downloadTask.run();
} else {
engine.submit(downloadTask);
}
}ImageLoaderEngine中添加了一个submit方法
//for downLoad tast
void submit(final DownloadTask task) {
taskDistributor.execute(new Runnable() {
@Override
public void run() {
File image = configuration.diskCache.get(task.getLoadingUri());
boolean isImageCachedOnDisk = image != null && image.exists();
initExecutorsIfNeed();
if (isImageCachedOnDisk) {
//do nothing.casue we have the image files already!
} else {
taskExecutor.execute(task);
}
}
});
}
由于实现的比较仓促，还有很多细节问题需要实现：
1，没有实现比如文件保存时没有resize图片大小。
2，还有如果刚刚添加了图片下载任务，这时候下拉刷新，就会图片就会增加一个加载并显示的任务，这时如果下载任务没完成，应该是取消下载任务（cancelDownloadTask），进行图片显示任务。更完善一点的是等待图片下载任务完成，再进行加载任务。这些细节就没有考虑了，所以进行时可能会有些问题。
优化
这个工程是基于上一篇文章的基础上修改优化的。http://blog.csdn.net/chen52671/article/details/44680765
原效果图如下：
ImageLoader加载
优化前
可以看出一个Page大概加载15张图片。如果是每个Item的getView时，触发item position+15的那个Item的图片的下载任务即可。
该效果图是对taobao加载宝贝图片的一个还原，可以看到起滑动刷新的时候，图片也是需要联网下载并加载，同样存在一定的延迟效果。
优化后：
优化后的ImageLoader加载
效果图看出，图片翻页时的加载速度明显提升，并且由于是直接缓存在本地硬盘，不会造成明显的内存占用，从一定程度上解决了翻页时的网络图片加载缓慢问题
优化修改主要在MyAdapter类。使用的ImageLoader是前面修改的版本。
MyAdapter
package com.example.gridpic;
import java.util.List;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;
import com.nostra13.universalimageloader.core.listener.DownloadListener;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
public class MyAdapter extends BaseAdapter {
List imageList;
protected ImageLoader imageLoader = ImageLoader.getInstance();
protected DisplayImageOptions options;
private LayoutInflater mInflater;
public Context context;
public MyAdapter(Context context, List imageList) {
super();
this.imageList = imageList;
this.context = context;
options = new DisplayImageOptions.Builder()
.showImageOnLoading(R.drawable.ic_launcher)
.showImageForEmptyUri(R.drawable.ic_launcher)
.showImageOnFail(R.drawable.ic_launcher).cacheInMemory(true)
.cacheOnDisk(true).bitmapConfig(Bitmap.Config.RGB_565).build();
this.mInflater = LayoutInflater.from(context);
// 初始化ImageLoader
ImageLoaderConfiguration.Builder config = new ImageLoaderConfiguration.Builder(
context);
config.threadPriority(Thread.NORM_PRIORITY - 2);
config.denyCacheImageMultipleSizesInMemory();
config.diskCacheFileNameGenerator(new Md5FileNameGenerator());
config.diskCacheSize(50 * 1024 * 1024); // 50 MiB
config.tasksProcessingOrder(QueueProcessingType.LIFO);
config.writeDebugLogs(); // Remove for release app
ImageLoader.getInstance().init(config.build());
}
@Override
public int getCount() {
return imageList.size();
}
@Override
public Object getItem(int arg0) {
// TODO Auto-generated method stub
return null;
}
@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return 0;
}
@Override
public View getView(int position, View view, ViewGroup viewGroup) {
ViewHolder holder = null;
if (view == null) {
view = mInflater.inflate(R.layout.picitem, null);
holder = new ViewHolder();
holder.image = (ImageView) view.findViewById(R.id.imageView1);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
imageLoader
.displayImage(imageList.get(position), holder.image, options);
//判断如果是Wifi环境，则采用Disc预加载策略
if (isWifi()) {
final int cachePosition = Math.min(position + 15,
imageList.size() - 1);
imageLoader.downloadImage(imageList.get(cachePosition), options,
new DownloadListener() {
@Override
public void onDownloadFailed(String arg0) {
}
@Override
public void onDownloadComplete(String arg0) {
Log.e("whatever", "Cache Image:" + cachePosition
+ ". url=" + imageList.get(cachePosition));
}
@Override
public void onDownloadCancelled(String arg0) {
}
@Override
public void OnDownloadStart(String arg0) {
}
});
}
Log.e("whatever",
"Get Image:" + position + ". url=" + imageList.get(position));
return view;
}
public boolean isWifi() {
ConnectivityManager connectivityManager = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetInfo = connectivityManager.getActiveNetworkInfo();
if (activeNetInfo != null
&& activeNetInfo.getType() == ConnectivityManager.TYPE_WIFI) {
return true;
}
return false;
}
final class ViewHolder {
public ImageView image;
}
}
加载图片的Log
从log中也能看出图片加载时的策略能够看出，图片的加载，下载的确是按照之前设想的思路进行的。
03-28 19:48:13.300: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=1
03-28 19:48:14.220: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=2
03-28 19:48:14.860: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=3
03-28 19:48:15.640: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=4
03-28 19:48:17.390: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=5
03-28 19:48:17.880: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=6
03-28 19:48:18.640: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=7
03-28 19:48:19.170: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=8
03-28 19:48:20.500: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=9
03-28 19:48:21.060: E/whatever(5315): URL ready
03-28 19:48:21.160: E/libEGL(5315): call to OpenGL ES API with no current context (logged once per thread)
03-28 19:48:21.160: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:21.170: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:21.170: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:21.170: E/whatever(5315): Get Image:1. url=http://file.juzimi.com/weibopic/jizxmd1.jpg
03-28 19:48:21.180: E/whatever(5315): Get Image:2. url=http://file.juzimi.com/weibopic/jrzdmd7.jpg
03-28 19:48:21.180: E/whatever(5315): Get Image:3. url=http://file.juzimi.com/weibopic/jozome2.jpg
03-28 19:48:21.180: E/whatever(5315): Get Image:4. url=http://file.juzimi.com/weibopic/jpzlmu7.jpg
03-28 19:48:21.180: E/whatever(5315): Get Image:5. url=http://file.juzimi.com/weibopic/jezimr6.jpg
03-28 19:48:21.190: E/whatever(5315): Get Image:6. url=http://file.juzimi.com/weibopic/jezemp2.jpg
03-28 19:48:21.190: E/whatever(5315): Get Image:7. url=http://file.juzimi.com/weibopic/jrzlmx2.jpg
03-28 19:48:21.190: E/whatever(5315): Get Image:8. url=http://file.juzimi.com/weibopic/jrzomd2.jpg
03-28 19:48:21.190: E/whatever(5315): Get Image:9. url=http://file.juzimi.com/weibopic/jizpml4.jpg
03-28 19:48:21.200: E/whatever(5315): Get Image:10. url=http://file.juzimi.com/weibopic/jezlmd1.jpg
03-28 19:48:21.200: E/whatever(5315): Get Image:11. url=http://file.juzimi.com/weibopic/jiziml3.jpg
03-28 19:48:21.200: E/whatever(5315): Get Image:12. url=http://file.juzimi.com/weibopic/jlzdmd3.jpg
03-28 19:48:21.200: E/whatever(5315): Get Image:13. url=http://file.juzimi.com/weibopic/jxzlmu2.jpg
03-28 19:48:21.210: E/whatever(5315): Get Image:14. url=http://file.juzimi.com/weibopic/jdzpmx2.jpg
03-28 19:48:22.090: E/whatever(5315): Cache Image:15. url=http://file.juzimi.com/weibopic/jezpma2.jpg
03-28 19:48:22.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:22.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:22.350: E/whatever(5315): Cache Image:29. url=http://file.juzimi.com/weibopic/juzlma7.jpg
03-28 19:48:22.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:22.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:23.120: E/whatever(5315): Cache Image:28. url=http://file.juzimi.com/weibopic/jpzoma2.jpg
03-28 19:48:23.370: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:23.380: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:23.790: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:23.790: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:23.890: E/whatever(5315): Cache Image:27. url=http://file.juzimi.com/weibopic/jazlml6.jpg
03-28 19:48:23.990: E/whatever(5315): Cache Image:26. url=http://file.juzimi.com/weibopic/jpzdmr2.jpg
03-28 19:48:24.270: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.270: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.270: E/whatever(5315): Cache Image:25. url=http://file.juzimi.com/weibopic/jezrmu5.jpg
03-28 19:48:24.500: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.510: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.600: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.610: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:24.770: E/whatever(5315): Cache Image:23. url=http://file.juzimi.com/weibopic/jazxmr4.jpg
03-28 19:48:25.510: E/whatever(5315): Cache Image:22. url=http://file.juzimi.com/weibopic/jozdme6.jpg
03-28 19:48:25.560: E/whatever(5315): Cache Image:24. url=http://file.juzimi.com/weibopic/jlzamd7.jpg
03-28 19:48:26.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.410: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.410: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:26.500: E/whatever(5315): Cache Image:20. url=http://file.juzimi.com/weibopic/juzdmd7.jpg
03-28 19:48:27.780: E/whatever(5315): Cache Image:21. url=http://file.juzimi.com/weibopic/jizdma2.jpg
03-28 19:48:28.030: E/whatever(5315): Cache Image:19. url=http://file.juzimi.com/weibopic/jizoma3.jpg
03-28 19:48:28.420: E/whatever(5315): Cache Image:18. url=http://file.juzimi.com/weibopic/juzlmx.jpg
03-28 19:48:28.420: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:28.420: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:28.800: E/whatever(5315): Cache Image:17. url=http://file.juzimi.com/weibopic/jpzxmr5.jpg
03-28 19:48:28.870: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:28.870: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:29.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:29.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:29.790: E/whatever(5315): Cache Image:16. url=http://file.juzimi.com/weibopic/jrzlmp2.jpg
03-28 19:48:30.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:30.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:30.490: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:30.490: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.540: E/whatever(5315): Get Image:15. url=http://file.juzimi.com/weibopic/jezpma2.jpg
03-28 19:48:32.540: E/whatever(5315): Get Image:16. url=http://file.juzimi.com/weibopic/jrzlmp2.jpg
03-28 19:48:32.550: E/whatever(5315): Get Image:17. url=http://file.juzimi.com/weibopic/jpzxmr5.jpg
03-28 19:48:32.640: E/whatever(5315): Get Image:18. url=http://file.juzimi.com/weibopic/juzlmx.jpg
03-28 19:48:32.640: E/whatever(5315): Get Image:19. url=http://file.juzimi.com/weibopic/jizoma3.jpg
03-28 19:48:32.650: E/whatever(5315): Get Image:20. url=http://file.juzimi.com/weibopic/juzdmd7.jpg
03-28 19:48:32.650: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.680: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.750: E/whatever(5315): Get Image:21. url=http://file.juzimi.com/weibopic/jizdma2.jpg
03-28 19:48:32.750: E/whatever(5315): Get Image:22. url=http://file.juzimi.com/weibopic/jozdme6.jpg
03-28 19:48:32.760: E/whatever(5315): Get Image:23. url=http://file.juzimi.com/weibopic/jazxmr4.jpg
03-28 19:48:32.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:32.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:33.280: E/whatever(5315): Cache Image:32. url=http://file.juzimi.com/weibopic/jpzrmp2.jpg
03-28 19:48:33.640: E/whatever(5315): Cache Image:31. url=http://file.juzimi.com/weibopic/jizomd2.jpg
03-28 19:48:34.080: E/whatever(5315): Cache Image:37. url=http://file.juzimi.com/weibopic/jazlmu4.jpg
03-28 19:48:34.100: E/whatever(5315): Cache Image:30. url=http://file.juzimi.com/weibopic/jxzimu1.jpg
03-28 19:48:34.110: E/whatever(5315): Get Image:24. url=http://file.juzimi.com/weibopic/jlzamd7.jpg
03-28 19:48:34.110: E/whatever(5315): Get Image:25. url=http://file.juzimi.com/weibopic/jezrmu5.jpg
03-28 19:48:34.110: E/whatever(5315): Get Image:26. url=http://file.juzimi.com/weibopic/jpzdmr2.jpg
03-28 19:48:34.190: E/whatever(5315): Get Image:27. url=http://file.juzimi.com/weibopic/jazlml6.jpg
03-28 19:48:34.190: E/whatever(5315): Get Image:28. url=http://file.juzimi.com/weibopic/jpzoma2.jpg
03-28 19:48:34.200: E/whatever(5315): Get Image:29. url=http://file.juzimi.com/weibopic/juzlma7.jpg
03-28 19:48:34.260: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.290: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.300: E/whatever(5315): Cache Image:38. url=http://file.juzimi.com/weibopic/jpzrmr5.jpg
03-28 19:48:34.300: E/whatever(5315): Cache Image:36. url=http://file.juzimi.com/weibopic/juzpma3.jpg
03-28 19:48:34.310: E/whatever(5315): Get Image:30. url=http://file.juzimi.com/weibopic/jxzimu1.jpg
03-28 19:48:34.310: E/whatever(5315): Get Image:31. url=http://file.juzimi.com/weibopic/jizomd2.jpg
03-28 19:48:34.310: E/whatever(5315): Get Image:32. url=http://file.juzimi.com/weibopic/jpzrmp2.jpg
03-28 19:48:34.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.400: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.430: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.440: E/whatever(5315): Cache Image:35. url=http://file.juzimi.com/weibopic/jozdmx.jpg
03-28 19:48:34.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.480: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.480: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:34.480: E/whatever(5315): Cache Image:43. url=http://file.juzimi.com/weibopic/juzpml2.jpg
03-28 19:48:34.930: E/whatever(5315): Cache Image:46. url=http://file.juzimi.com/weibopic/jpzomr5.jpg
03-28 19:48:35.090: E/whatever(5315): Cache Image:44. url=http://file.juzimi.com/weibopic/jozxml1.jpg
03-28 19:48:35.530: E/whatever(5315): Cache Image:47. url=http://file.juzimi.com/weibopic/jozamp7.jpg
03-28 19:48:35.550: E/whatever(5315): Get Image:33. url=http://file.juzimi.com/weibopic/jpzomr.jpg
03-28 19:48:35.560: E/whatever(5315): Get Image:34. url=http://file.juzimi.com/weibopic/juzomr5.jpg
03-28 19:48:35.560: E/whatever(5315): Get Image:35. url=http://file.juzimi.com/weibopic/jozdmx.jpg
03-28 19:48:35.610: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.620: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.640: E/whatever(5315): Get Image:36. url=http://file.juzimi.com/weibopic/juzpma3.jpg
03-28 19:48:35.640: E/whatever(5315): Get Image:37. url=http://file.juzimi.com/weibopic/jazlmu4.jpg
03-28 19:48:35.640: E/whatever(5315): Get Image:38. url=http://file.juzimi.com/weibopic/jpzrmr5.jpg
03-28 19:48:35.720: E/whatever(5315): Get Image:39. url=http://file.juzimi.com/weibopic/jxzlmx5.jpg
03-28 19:48:35.720: E/whatever(5315): Get Image:40. url=http://file.juzimi.com/weibopic/jezlmo3.jpg
03-28 19:48:35.720: E/whatever(5315): Get Image:41. url=http://file.juzimi.com/weibopic/jozeml6.jpg
03-28 19:48:35.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.790: E/whatever(5315): Get Image:42. url=http://file.juzimi.com/weibopic/jlzomi.jpg
03-28 19:48:35.800: E/whatever(5315): Get Image:43. url=http://file.juzimi.com/weibopic/juzpml2.jpg
03-28 19:48:35.800: E/whatever(5315): Get Image:44. url=http://file.juzimi.com/weibopic/jozxml1.jpg
03-28 19:48:35.830: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.830: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.880: E/whatever(5315): Cache Image:45. url=http://file.juzimi.com/weibopic/jdzama3.jpg
03-28 19:48:35.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.910: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:35.910: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.120: E/whatever(5315): Cache Image:42. url=http://file.juzimi.com/weibopic/jlzomi.jpg
03-28 19:48:36.180: E/whatever(5315): Cache Image:59. url=http://file.juzimi.com/weibopic/juzxmo7.jpg
03-28 19:48:36.230: E/whatever(5315): Cache Image:41. url=http://file.juzimi.com/weibopic/jozeml6.jpg
03-28 19:48:36.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.490: E/whatever(5315): Cache Image:58. url=http://file.juzimi.com/weibopic/jrzome.jpg
03-28 19:48:36.810: E/whatever(5315): Cache Image:57. url=http://file.juzimi.com/weibopic/jxzomr3.jpg
03-28 19:48:36.910: E/whatever(5315): Cache Image:54. url=http://file.juzimi.com/weibopic/jizemr.jpg
03-28 19:48:36.940: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.940: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:36.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:37.170: E/whatever(5315): Cache Image:56. url=http://file.juzimi.com/weibopic/jezomx5.jpg
03-28 19:48:37.240: E/whatever(5315): Cache Image:55. url=http://file.juzimi.com/weibopic/jezdmu7.jpg
03-28 19:48:37.600: E/whatever(5315): Cache Image:53. url=http://file.juzimi.com/weibopic/jrzomr3.jpg
03-28 19:48:37.890: E/whatever(5315): Cache Image:52. url=http://file.juzimi.com/weibopic/jozomr7.jpg
03-28 19:48:38.560: E/whatever(5315): Cache Image:51. url=http://file.juzimi.com/weibopic/jozume4.jpg
03-28 19:48:38.590: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:38.590: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:38.870: E/whatever(5315): Cache Image:50. url=http://file.juzimi.com/weibopic/jazrmp6.jpg
03-28 19:48:38.900: E/whatever(5315): Cache Image:49. url=http://file.juzimi.com/weibopic/jrzumi2.jpg
03-28 19:48:38.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:38.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:39.120: E/whatever(5315): Cache Image:48. url=http://file.juzimi.com/weibopic/jizeme7.jpg
03-28 19:48:39.140: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:39.140: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.150: E/whatever(5315): Get Image:45. url=http://file.juzimi.com/weibopic/jdzama3.jpg
03-28 19:48:40.160: E/whatever(5315): Get Image:46. url=http://file.juzimi.com/weibopic/jpzomr5.jpg
03-28 19:48:40.160: E/whatever(5315): Get Image:47. url=http://file.juzimi.com/weibopic/jozamp7.jpg
03-28 19:48:40.250: E/whatever(5315): Get Image:48. url=http://file.juzimi.com/weibopic/jizeme7.jpg
03-28 19:48:40.260: E/whatever(5315): Get Image:49. url=http://file.juzimi.com/weibopic/jrzumi2.jpg
03-28 19:48:40.260: E/whatever(5315): Get Image:50. url=http://file.juzimi.com/weibopic/jazrmp6.jpg
03-28 19:48:40.330: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.330: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.380: E/whatever(5315): Get Image:51. url=http://file.juzimi.com/weibopic/jozume4.jpg
03-28 19:48:40.380: E/whatever(5315): Get Image:52. url=http://file.juzimi.com/weibopic/jozomr7.jpg
03-28 19:48:40.380: E/whatever(5315): Get Image:53. url=http://file.juzimi.com/weibopic/jrzomr3.jpg
03-28 19:48:40.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.460: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.460: E/whatever(5315): Cache Image:61. url=http://file.juzimi.com/weibopic/jezema5.jpg
03-28 19:48:40.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:40.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.150: E/whatever(5315): Cache Image:68. url=http://file.juzimi.com/weibopic/jlzoml.jpg
03-28 19:48:41.180: E/whatever(5315): Cache Image:60. url=http://file.juzimi.com/weibopic/juzxmi4.jpg
03-28 19:48:41.540: E/whatever(5315): Get Image:54. url=http://file.juzimi.com/weibopic/jizemr.jpg
03-28 19:48:41.540: E/whatever(5315): Get Image:55. url=http://file.juzimi.com/weibopic/jezdmu7.jpg
03-28 19:48:41.540: E/whatever(5315): Get Image:56. url=http://file.juzimi.com/weibopic/jezomx5.jpg
03-28 19:48:41.590: E/whatever(5315): Get Image:57. url=http://file.juzimi.com/weibopic/jxzomr3.jpg
03-28 19:48:41.590: E/whatever(5315): Get Image:58. url=http://file.juzimi.com/weibopic/jrzome.jpg
03-28 19:48:41.600: E/whatever(5315): Get Image:59. url=http://file.juzimi.com/weibopic/juzxmo7.jpg
03-28 19:48:41.600: E/whatever(5315): Cache Image:66. url=http://file.juzimi.com/weibopic/jezumu3.jpg
03-28 19:48:41.640: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.640: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.720: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.720: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:41.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:42.670: E/whatever(5315): Cache Image:73. url=http://file.juzimi.com/weibopic/jazxmd6.jpg
03-28 19:48:42.770: E/whatever(5315): Get Image:60. url=http://file.juzimi.com/weibopic/juzxmi4.jpg
03-28 19:48:42.770: E/whatever(5315): Get Image:61. url=http://file.juzimi.com/weibopic/jezema5.jpg
03-28 19:48:42.770: E/whatever(5315): Cache Image:62. url=http://file.juzimi.com/weibopic/jlzrmd4.jpg
03-28 19:48:42.780: E/whatever(5315): Get Image:62. url=http://file.juzimi.com/weibopic/jlzrmd4.jpg
03-28 19:48:42.860: E/whatever(5315): Get Image:63. url=http://file.juzimi.com/weibopic/jxzomo6.jpg
03-28 19:48:42.860: E/whatever(5315): Get Image:64. url=http://file.juzimi.com/weibopic/juzpmi.jpg
03-28 19:48:42.860: E/whatever(5315): Get Image:65. url=http://file.juzimi.com/weibopic/jizemx1.jpg
03-28 19:48:42.880: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:42.880: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:42.880: E/whatever(5315): Cache Image:67. url=http://file.juzimi.com/weibopic/jrzumi7.jpg
03-28 19:48:42.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:42.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg
03-28 19:48:42.940: E/whatever(5315): Get Image:66. url=http://file.juzimi.com/weibopic/jezumu3.jpg
03-28 19:48:42.940: E/whatever(5315): Get Image:67. url=http://file.juzimi.com/weibopic/jrzumi7.jpg
03-28 19:48:42.940: E/whatever(5315): Get Image:68. url=http://file.juzimi.com/weibopic/jlzoml.jpg
后记
根据效果图可以看出，在浏览时停留几秒，然后滑动页面，加载速度的确会快了些。不过除了上面说到的ImageLoader存在的问题外。图片加载时还存在如下细节问题：
1，Page1的15张图片加载时，同时第16-30张图片也会加入到下载队列，这就造成了第一页的15张图片加载缓慢。
解决方法：方法1:修改ImageLoader让下载任务的优先级降低。方法2：在工程中当前显示的图片任务都显示完毕后，在完成的回调中再加入下载任务。
2，当图片滑动过快的时候，比如从第1页，直接滑到了第5页，那234页在工程中还是要一步步的下载。而为了用户体验更好，那234页是没必要下载，或者最晚下载的。能想到的比较好的方法就是，显示到哪些item了，那就计算出之前的哪些item已经不在屏幕内了，然后cancel掉下载的任务。或者改变那些下载任务的优先级。
3, 不论是图片显示，还是图片下载，添加任务的时候是按照图片顺序添加的，完成却是按照逆序完成的。原因是Imageloader设定成了tasksProcessingOrder(QueueProcessingType.LIFO)，不过不影响实际效果，根据项目需求设定吧。
以上为抛砖引玉，仅供参考 , 欢迎讨论。