Android网络图片加载优化
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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 <b>true</b> - if current task was interrupted; <b>false</b> - * 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<String> imageList; protected ImageLoader imageLoader = ImageLoader.getInstance(); protected DisplayImageOptions options; private LayoutInflater mInflater; public Context context; public MyAdapter(Context context, List<String> 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=103-28 19:48:14.220: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=203-28 19:48:14.860: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=303-28 19:48:15.640: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=403-28 19:48:17.390: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=503-28 19:48:17.880: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=603-28 19:48:18.640: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=703-28 19:48:19.170: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=803-28 19:48:20.500: E/whatever(5315): http://www.juzimi.com/meitumeiju?page=903-28 19:48:21.060: E/whatever(5315): URL ready03-28 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.jpg03-28 19:48:21.170: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:21.170: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:21.170: E/whatever(5315): Get Image:1. url=http://file.juzimi.com/weibopic/jizxmd1.jpg03-28 19:48:21.180: E/whatever(5315): Get Image:2. url=http://file.juzimi.com/weibopic/jrzdmd7.jpg03-28 19:48:21.180: E/whatever(5315): Get Image:3. url=http://file.juzimi.com/weibopic/jozome2.jpg03-28 19:48:21.180: E/whatever(5315): Get Image:4. url=http://file.juzimi.com/weibopic/jpzlmu7.jpg03-28 19:48:21.180: E/whatever(5315): Get Image:5. url=http://file.juzimi.com/weibopic/jezimr6.jpg03-28 19:48:21.190: E/whatever(5315): Get Image:6. url=http://file.juzimi.com/weibopic/jezemp2.jpg03-28 19:48:21.190: E/whatever(5315): Get Image:7. url=http://file.juzimi.com/weibopic/jrzlmx2.jpg03-28 19:48:21.190: E/whatever(5315): Get Image:8. url=http://file.juzimi.com/weibopic/jrzomd2.jpg03-28 19:48:21.190: E/whatever(5315): Get Image:9. url=http://file.juzimi.com/weibopic/jizpml4.jpg03-28 19:48:21.200: E/whatever(5315): Get Image:10. url=http://file.juzimi.com/weibopic/jezlmd1.jpg03-28 19:48:21.200: E/whatever(5315): Get Image:11. url=http://file.juzimi.com/weibopic/jiziml3.jpg03-28 19:48:21.200: E/whatever(5315): Get Image:12. url=http://file.juzimi.com/weibopic/jlzdmd3.jpg03-28 19:48:21.200: E/whatever(5315): Get Image:13. url=http://file.juzimi.com/weibopic/jxzlmu2.jpg03-28 19:48:21.210: E/whatever(5315): Get Image:14. url=http://file.juzimi.com/weibopic/jdzpmx2.jpg03-28 19:48:22.090: E/whatever(5315): Cache Image:15. url=http://file.juzimi.com/weibopic/jezpma2.jpg03-28 19:48:22.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:22.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:22.350: E/whatever(5315): Cache Image:29. url=http://file.juzimi.com/weibopic/juzlma7.jpg03-28 19:48:22.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:22.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:23.120: E/whatever(5315): Cache Image:28. url=http://file.juzimi.com/weibopic/jpzoma2.jpg03-28 19:48:23.370: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:23.380: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:23.790: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:23.790: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:23.890: E/whatever(5315): Cache Image:27. url=http://file.juzimi.com/weibopic/jazlml6.jpg03-28 19:48:23.990: E/whatever(5315): Cache Image:26. url=http://file.juzimi.com/weibopic/jpzdmr2.jpg03-28 19:48:24.270: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.270: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.270: E/whatever(5315): Cache Image:25. url=http://file.juzimi.com/weibopic/jezrmu5.jpg03-28 19:48:24.500: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.510: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.600: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.610: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:24.770: E/whatever(5315): Cache Image:23. url=http://file.juzimi.com/weibopic/jazxmr4.jpg03-28 19:48:25.510: E/whatever(5315): Cache Image:22. url=http://file.juzimi.com/weibopic/jozdme6.jpg03-28 19:48:25.560: E/whatever(5315): Cache Image:24. url=http://file.juzimi.com/weibopic/jlzamd7.jpg03-28 19:48:26.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.300: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.410: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.410: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.440: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:26.500: E/whatever(5315): Cache Image:20. url=http://file.juzimi.com/weibopic/juzdmd7.jpg03-28 19:48:27.780: E/whatever(5315): Cache Image:21. url=http://file.juzimi.com/weibopic/jizdma2.jpg03-28 19:48:28.030: E/whatever(5315): Cache Image:19. url=http://file.juzimi.com/weibopic/jizoma3.jpg03-28 19:48:28.420: E/whatever(5315): Cache Image:18. url=http://file.juzimi.com/weibopic/juzlmx.jpg03-28 19:48:28.420: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:28.420: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:28.800: E/whatever(5315): Cache Image:17. url=http://file.juzimi.com/weibopic/jpzxmr5.jpg03-28 19:48:28.870: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:28.870: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:29.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:29.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:29.790: E/whatever(5315): Cache Image:16. url=http://file.juzimi.com/weibopic/jrzlmp2.jpg03-28 19:48:30.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:30.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:30.490: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:30.490: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.540: E/whatever(5315): Get Image:15. url=http://file.juzimi.com/weibopic/jezpma2.jpg03-28 19:48:32.540: E/whatever(5315): Get Image:16. url=http://file.juzimi.com/weibopic/jrzlmp2.jpg03-28 19:48:32.550: E/whatever(5315): Get Image:17. url=http://file.juzimi.com/weibopic/jpzxmr5.jpg03-28 19:48:32.640: E/whatever(5315): Get Image:18. url=http://file.juzimi.com/weibopic/juzlmx.jpg03-28 19:48:32.640: E/whatever(5315): Get Image:19. url=http://file.juzimi.com/weibopic/jizoma3.jpg03-28 19:48:32.650: E/whatever(5315): Get Image:20. url=http://file.juzimi.com/weibopic/juzdmd7.jpg03-28 19:48:32.650: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.680: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.750: E/whatever(5315): Get Image:21. url=http://file.juzimi.com/weibopic/jizdma2.jpg03-28 19:48:32.750: E/whatever(5315): Get Image:22. url=http://file.juzimi.com/weibopic/jozdme6.jpg03-28 19:48:32.760: E/whatever(5315): Get Image:23. url=http://file.juzimi.com/weibopic/jazxmr4.jpg03-28 19:48:32.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:32.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:33.280: E/whatever(5315): Cache Image:32. url=http://file.juzimi.com/weibopic/jpzrmp2.jpg03-28 19:48:33.640: E/whatever(5315): Cache Image:31. url=http://file.juzimi.com/weibopic/jizomd2.jpg03-28 19:48:34.080: E/whatever(5315): Cache Image:37. url=http://file.juzimi.com/weibopic/jazlmu4.jpg03-28 19:48:34.100: E/whatever(5315): Cache Image:30. url=http://file.juzimi.com/weibopic/jxzimu1.jpg03-28 19:48:34.110: E/whatever(5315): Get Image:24. url=http://file.juzimi.com/weibopic/jlzamd7.jpg03-28 19:48:34.110: E/whatever(5315): Get Image:25. url=http://file.juzimi.com/weibopic/jezrmu5.jpg03-28 19:48:34.110: E/whatever(5315): Get Image:26. url=http://file.juzimi.com/weibopic/jpzdmr2.jpg03-28 19:48:34.190: E/whatever(5315): Get Image:27. url=http://file.juzimi.com/weibopic/jazlml6.jpg03-28 19:48:34.190: E/whatever(5315): Get Image:28. url=http://file.juzimi.com/weibopic/jpzoma2.jpg03-28 19:48:34.200: E/whatever(5315): Get Image:29. url=http://file.juzimi.com/weibopic/juzlma7.jpg03-28 19:48:34.260: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.290: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.300: E/whatever(5315): Cache Image:38. url=http://file.juzimi.com/weibopic/jpzrmr5.jpg03-28 19:48:34.300: E/whatever(5315): Cache Image:36. url=http://file.juzimi.com/weibopic/juzpma3.jpg03-28 19:48:34.310: E/whatever(5315): Get Image:30. url=http://file.juzimi.com/weibopic/jxzimu1.jpg03-28 19:48:34.310: E/whatever(5315): Get Image:31. url=http://file.juzimi.com/weibopic/jizomd2.jpg03-28 19:48:34.310: E/whatever(5315): Get Image:32. url=http://file.juzimi.com/weibopic/jpzrmp2.jpg03-28 19:48:34.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.400: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.430: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.440: E/whatever(5315): Cache Image:35. url=http://file.juzimi.com/weibopic/jozdmx.jpg03-28 19:48:34.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.480: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.480: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:34.480: E/whatever(5315): Cache Image:43. url=http://file.juzimi.com/weibopic/juzpml2.jpg03-28 19:48:34.930: E/whatever(5315): Cache Image:46. url=http://file.juzimi.com/weibopic/jpzomr5.jpg03-28 19:48:35.090: E/whatever(5315): Cache Image:44. url=http://file.juzimi.com/weibopic/jozxml1.jpg03-28 19:48:35.530: E/whatever(5315): Cache Image:47. url=http://file.juzimi.com/weibopic/jozamp7.jpg03-28 19:48:35.550: E/whatever(5315): Get Image:33. url=http://file.juzimi.com/weibopic/jpzomr.jpg03-28 19:48:35.560: E/whatever(5315): Get Image:34. url=http://file.juzimi.com/weibopic/juzomr5.jpg03-28 19:48:35.560: E/whatever(5315): Get Image:35. url=http://file.juzimi.com/weibopic/jozdmx.jpg03-28 19:48:35.610: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.620: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.640: E/whatever(5315): Get Image:36. url=http://file.juzimi.com/weibopic/juzpma3.jpg03-28 19:48:35.640: E/whatever(5315): Get Image:37. url=http://file.juzimi.com/weibopic/jazlmu4.jpg03-28 19:48:35.640: E/whatever(5315): Get Image:38. url=http://file.juzimi.com/weibopic/jpzrmr5.jpg03-28 19:48:35.720: E/whatever(5315): Get Image:39. url=http://file.juzimi.com/weibopic/jxzlmx5.jpg03-28 19:48:35.720: E/whatever(5315): Get Image:40. url=http://file.juzimi.com/weibopic/jezlmo3.jpg03-28 19:48:35.720: E/whatever(5315): Get Image:41. url=http://file.juzimi.com/weibopic/jozeml6.jpg03-28 19:48:35.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.790: E/whatever(5315): Get Image:42. url=http://file.juzimi.com/weibopic/jlzomi.jpg03-28 19:48:35.800: E/whatever(5315): Get Image:43. url=http://file.juzimi.com/weibopic/juzpml2.jpg03-28 19:48:35.800: E/whatever(5315): Get Image:44. url=http://file.juzimi.com/weibopic/jozxml1.jpg03-28 19:48:35.830: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.830: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.880: E/whatever(5315): Cache Image:45. url=http://file.juzimi.com/weibopic/jdzama3.jpg03-28 19:48:35.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.890: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.910: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:35.910: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.120: E/whatever(5315): Cache Image:42. url=http://file.juzimi.com/weibopic/jlzomi.jpg03-28 19:48:36.180: E/whatever(5315): Cache Image:59. url=http://file.juzimi.com/weibopic/juzxmo7.jpg03-28 19:48:36.230: E/whatever(5315): Cache Image:41. url=http://file.juzimi.com/weibopic/jozeml6.jpg03-28 19:48:36.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.320: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.490: E/whatever(5315): Cache Image:58. url=http://file.juzimi.com/weibopic/jrzome.jpg03-28 19:48:36.810: E/whatever(5315): Cache Image:57. url=http://file.juzimi.com/weibopic/jxzomr3.jpg03-28 19:48:36.910: E/whatever(5315): Cache Image:54. url=http://file.juzimi.com/weibopic/jizemr.jpg03-28 19:48:36.940: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.940: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:36.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:37.170: E/whatever(5315): Cache Image:56. url=http://file.juzimi.com/weibopic/jezomx5.jpg03-28 19:48:37.240: E/whatever(5315): Cache Image:55. url=http://file.juzimi.com/weibopic/jezdmu7.jpg03-28 19:48:37.600: E/whatever(5315): Cache Image:53. url=http://file.juzimi.com/weibopic/jrzomr3.jpg03-28 19:48:37.890: E/whatever(5315): Cache Image:52. url=http://file.juzimi.com/weibopic/jozomr7.jpg03-28 19:48:38.560: E/whatever(5315): Cache Image:51. url=http://file.juzimi.com/weibopic/jozume4.jpg03-28 19:48:38.590: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:38.590: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:38.870: E/whatever(5315): Cache Image:50. url=http://file.juzimi.com/weibopic/jazrmp6.jpg03-28 19:48:38.900: E/whatever(5315): Cache Image:49. url=http://file.juzimi.com/weibopic/jrzumi2.jpg03-28 19:48:38.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:38.970: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:39.120: E/whatever(5315): Cache Image:48. url=http://file.juzimi.com/weibopic/jizeme7.jpg03-28 19:48:39.140: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:39.140: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.150: E/whatever(5315): Get Image:45. url=http://file.juzimi.com/weibopic/jdzama3.jpg03-28 19:48:40.160: E/whatever(5315): Get Image:46. url=http://file.juzimi.com/weibopic/jpzomr5.jpg03-28 19:48:40.160: E/whatever(5315): Get Image:47. url=http://file.juzimi.com/weibopic/jozamp7.jpg03-28 19:48:40.250: E/whatever(5315): Get Image:48. url=http://file.juzimi.com/weibopic/jizeme7.jpg03-28 19:48:40.260: E/whatever(5315): Get Image:49. url=http://file.juzimi.com/weibopic/jrzumi2.jpg03-28 19:48:40.260: E/whatever(5315): Get Image:50. url=http://file.juzimi.com/weibopic/jazrmp6.jpg03-28 19:48:40.330: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.330: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.380: E/whatever(5315): Get Image:51. url=http://file.juzimi.com/weibopic/jozume4.jpg03-28 19:48:40.380: E/whatever(5315): Get Image:52. url=http://file.juzimi.com/weibopic/jozomr7.jpg03-28 19:48:40.380: E/whatever(5315): Get Image:53. url=http://file.juzimi.com/weibopic/jrzomr3.jpg03-28 19:48:40.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.390: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.450: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.460: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.460: E/whatever(5315): Cache Image:61. url=http://file.juzimi.com/weibopic/jezema5.jpg03-28 19:48:40.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:40.520: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.150: E/whatever(5315): Cache Image:68. url=http://file.juzimi.com/weibopic/jlzoml.jpg03-28 19:48:41.180: E/whatever(5315): Cache Image:60. url=http://file.juzimi.com/weibopic/juzxmi4.jpg03-28 19:48:41.540: E/whatever(5315): Get Image:54. url=http://file.juzimi.com/weibopic/jizemr.jpg03-28 19:48:41.540: E/whatever(5315): Get Image:55. url=http://file.juzimi.com/weibopic/jezdmu7.jpg03-28 19:48:41.540: E/whatever(5315): Get Image:56. url=http://file.juzimi.com/weibopic/jezomx5.jpg03-28 19:48:41.590: E/whatever(5315): Get Image:57. url=http://file.juzimi.com/weibopic/jxzomr3.jpg03-28 19:48:41.590: E/whatever(5315): Get Image:58. url=http://file.juzimi.com/weibopic/jrzome.jpg03-28 19:48:41.600: E/whatever(5315): Get Image:59. url=http://file.juzimi.com/weibopic/juzxmo7.jpg03-28 19:48:41.600: E/whatever(5315): Cache Image:66. url=http://file.juzimi.com/weibopic/jezumu3.jpg03-28 19:48:41.640: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.640: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.720: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.720: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.740: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:41.760: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:42.670: E/whatever(5315): Cache Image:73. url=http://file.juzimi.com/weibopic/jazxmd6.jpg03-28 19:48:42.770: E/whatever(5315): Get Image:60. url=http://file.juzimi.com/weibopic/juzxmi4.jpg03-28 19:48:42.770: E/whatever(5315): Get Image:61. url=http://file.juzimi.com/weibopic/jezema5.jpg03-28 19:48:42.770: E/whatever(5315): Cache Image:62. url=http://file.juzimi.com/weibopic/jlzrmd4.jpg03-28 19:48:42.780: E/whatever(5315): Get Image:62. url=http://file.juzimi.com/weibopic/jlzrmd4.jpg03-28 19:48:42.860: E/whatever(5315): Get Image:63. url=http://file.juzimi.com/weibopic/jxzomo6.jpg03-28 19:48:42.860: E/whatever(5315): Get Image:64. url=http://file.juzimi.com/weibopic/juzpmi.jpg03-28 19:48:42.860: E/whatever(5315): Get Image:65. url=http://file.juzimi.com/weibopic/jizemx1.jpg03-28 19:48:42.880: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:42.880: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:42.880: E/whatever(5315): Cache Image:67. url=http://file.juzimi.com/weibopic/jrzumi7.jpg03-28 19:48:42.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:42.900: E/whatever(5315): Get Image:0. url=http://file.juzimi.com/weibopic/jlzumo3.jpg03-28 19:48:42.940: E/whatever(5315): Get Image:66. url=http://file.juzimi.com/weibopic/jezumu3.jpg03-28 19:48:42.940: E/whatever(5315): Get Image:67. url=http://file.juzimi.com/weibopic/jrzumi7.jpg03-28 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。
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