android 图片缓存

原理示意图

    主体有三个，分别是UI，缓存模块和数据源（网络）。它们之间的关系如下：



① UI：请求数据，使用唯一的Key值索引Memory Cache中的Bitmap。

② 内存缓存：缓存搜索，如果能找到Key值对应的Bitmap，则返回数据。否则执行第三步。

③ 硬盘存储：使用唯一Key值对应的文件名，检索SDCard上的文件。

④ 如果有对应文件，使用BitmapFactory.decode*方法，解码Bitmap并返回数据，同时将数据写入缓存。如果没有对应文件，执行第五步。

⑤ 下载图片：启动异步线程，从数据源下载数据(Web)。

⑥ 若下载成功，将数据同时写入硬盘和缓存，并将Bitmap显示在UI中。

目前比较主流的图片缓存框架



Glide和Picasso都是非常完美的库。Glide加载图像以及磁盘缓存的方式都要优于Picasso，速度更快，并且Glide更有利于减少OutOfMemoryError的发生，GIF动画是Glide的杀手锏。不过Picasso的图片质量更高。Universal
Image Loader：一个强大的图片加载库，包含各种各样的配置，最老牌，使用也最广泛。

其中内存缓存主要是通过LRUCache实现的。讲到LruCache不得不提一下LinkedHashMap，因为LruCache中Lru算法的实现就是通过LinkedHashMap来实现的。LinkedHashMap继承于HashMap，它使用了一个双向链表来存储Map中的Entry顺序关系，这种顺序有两种，一种是LRU顺序，一种是插入顺序，这可以由其构造函数public
LinkedHashMap(int initialCapacity,float loadFactor, boolean accessOrder)指定。所以，对于get、put、remove等操作，LinkedHashMap除了要做HashMap做的事情，还做些调整Entry顺序链表的工作。LruCache中将LinkedHashMap的顺序设置为LRU顺序来实现LRU缓存，每次调用get(也就是从内存缓存中取图片)，则将该对象移到链表的尾端。调用put插入新的对象也是存储在链表尾端，这样当内存缓存达到设定的最大值时，将链表头部的对象（近期最少用到的）移除。
package com.example.renlei.myapplication.imageload.myimageload;

import android.graphics.Bitmap;
import android.util.Log;
import android.util.LruCache;

/**
* Created by renlei
* DATE: 16/6/28
* Time: 15:53
*/
public class MemoryCache {
public static LruCache<String, Bitmap> mMemoryCache;

public static void init() {
int maxSize = (int) (Runtime.getRuntime().maxMemory() / 1024);
int cacheSize = maxSize / 8;
if (mMemoryCache == null){
mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getByteCount() / 1024;
}
};
}
}

public static synchronized void addToMemory(String key, Bitmap bitmap) {
if (key != null && bitmap != null) {
Log.d("BitmapCaChe", "addToMemory" + "key" + DiskCache.getFilepath(key));
Log.d("BitmapCaChe", "size" + mMemoryCache.size() + "map");
mMemoryCache.put(DiskCache.getFilepath(key), bitmap);
}

}

public static synchronized Bitmap getMemory(String key) {
if (mMemoryCache != null && key != null){
Log.d("BitmapCaChe", "getMemory" + "key" + DiskCache.getFilepath(key) + "从缓存中进行加载");
return mMemoryCache.get(DiskCache.getFilepath(key));
}
return null;
}

}
磁盘缓存
主要就是将从网络获取的图片存到本地中
package com.example.renlei.myapplication.imageload.myimageload;

import android.text.TextUtils;
import android.util.Log;

import com.example.renlei.myapplication.MyApplication;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
* Created by renlei
* DATE: 16/6/29
* Time: 15:21
*/
public class DiskCache {
private volatile static DiskCache instance;

public static DiskCache getInstance() {
if (instance == null) {
synchronized (DiskCache.class) {
if (instance == null) {
instance = new DiskCache();
}
}
}
return instance;
}

private static String cachePath;

static {
cachePath = MyApplication.getContext().getExternalCacheDir() + "/img";
File file = new File(cachePath);
file.mkdirs();

}

public boolean save(String imgUrl, InputStream inputStream) {
if (TextUtils.isEmpty(imgUrl) || inputStream == null) {
return false;
}
String filePath = getFilepath(imgUrl);
File file = new File(filePath);

FileOutputStream fos = null;
try {
if (!file.exists()) {
file.createNewFile();
}
fos = new FileOutputStream(file);
byte[] buffer = new byte[1024];
int n;
while ((n = inputStream.read(buffer)) != -1) {
fos.write(buffer, 0, n);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
inputStream.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Log.d("DiskCache", "save disk" + " " + filePath);
return true;
}

public File get(String imgUrl) {
String filePath = getFilepath(imgUrl);
File file = new File(filePath);
if (file.exists()) {
Log.d("DiskCache", "get disk" + " " + filePath);
return file;
}
return null;
}

public static String getFilepath(String url) {
if (url.contains("/")) {
String[] urls = url.split("/");
return cachePath + File.separator + urls[urls.length - 1];
}
return url;
}

}
Listview的 Adapter
package com.example.renlei.myapplication.imageload.myimageload;

import android.content.Context;
import android.graphics.Bitmap;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;

import com.example.renlei.myapplication.R;
import com.example.renlei.myapplication.baseandroid.chapterfour.BitmapCache;
import com.example.renlei.myapplication.baseandroid.chapterfour.BitmapTask;

import java.util.ArrayList;
import java.util.List;

/**
* Created by renlei
* DATE: 16/6/28
* Time: 14:36
*/
public class MyImageLoadAdapter extends BaseAdapter {
LayoutInflater inflater;
Context mContext;
int length;
public MyImageLoadAdapter(Context mContext) {
this.mContext = mContext;
inflater = LayoutInflater.from(mContext);
}

@Override
public int getCount() {
return ImageUrlConstant.imgUrls.length;
}

@Override
public Object getItem(int position) {
return ImageUrlConstant.imgUrls[position];
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
convertView = inflater.inflate(R.layout.image_load_item, null);
viewHolder = new ViewHolder(convertView);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
ImageLoad.loadImage(viewHolder.iv,ImageUrlConstant.imgUrls[position],null);
return convertView;
}

static class ViewHolder {
ImageView iv;

public ViewHolder(View rootView) {
iv = (ImageView) rootView.findViewById(R.id.iv);
}
}

}

ImageLoad加载的核心类
主要思想是，先从缓存中查找图片，如果没有的话，就从磁盘中查找，如果磁盘中也没有的话，就需要从网页中进行下载
package com.example.renlei.myapplication.imageload.myimageload;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.text.TextUtils;
import android.util.Log;
import android.widget.ImageView;

import com.example.renlei.myapplication.R;

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
* Created by renlei
* DATE: 16/6/29
* Time: 15:18
*/
public class ImageLoad {
private static ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(3, 5, 30, TimeUnit.SECONDS, new LinkedBlockingDeque<Runnable>(10), new RejectDone());

static class RejectDone extends ThreadPoolExecutor.AbortPolicy {
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
// super.rejectedExecution(r, e);
// Log.d(TAG, ((ThreadPoolTask) r).taskName + "被阻止");
}
}

public static void loadImage(ImageView iv, String url, BitmapFactory.Options options) {
if (iv == null) {
return;
}
if (TextUtils.isEmpty(url)) {
iv.setImageResource(R.mipmap.ic_launcher);
return;
}
/**
* 从缓存中进行读取
*/
Bitmap memoryBitmap = MemoryCache.getMemory(url);
if (memoryBitmap != null) {
Log.d("ImageLoad", "从缓存中进行加载");
iv.setImageBitmap(memoryBitmap);
return;
}
/**
* 缓存中没有，设置默认图
*/
iv.setImageResource(R.mipmap.ic_launcher);
iv.setTag(url);//设置tag防止错位
/**
* 从硬盘中查询
*/
poolExecutor.execute(new ImageLoadTask(url,iv));
}
}
其中要注意必须要给ImageView设置一个Tag，否则的话会出现图片错位以及跳跃的现象。可以参考

android listview 异步加载图片并防止错位

ImageLoadTask
用来下载图片以及展示图片的异步任务
package com.example.renlei.myapplication.imageload.myimageload;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.text.TextUtils;
import android.util.Log;
import android.widget.ImageView;

import java.io.File;
import java.net.HttpURLConnection;
import java.net.URL;

/**
* Created by renlei
* DATE: 16/6/29
* Time: 16:23
*/
public class ImageLoadTask implements Runnable {
String imaUrl;
ImageView mIV;
DiskCache diskCache = DiskCache.getInstance();

public ImageLoadTask(String imaUrl, ImageView imageView) {
this.imaUrl = imaUrl;
mIV = imageView;
}

@Override
public void run() {
Log.d("ImageLoad", "ImageLoadTaskRun");
if (TextUtils.isEmpty(imaUrl)) {
return;
}
File file = diskCache.get(imaUrl);
if (file != null) {///瓷盘中有从磁盘中加载
Log.d("ImageLoad", "从瓷盘中加载");
final Bitmap bitmap = decodeFileToBitmap(file);
if (mIV.getTag() != null && mIV.getTag().equals(imaUrl)) {
mIV.post(new Runnable() {
@Override
public void run() {
mIV.setImageBitmap(bitmap);
}
});
}
MemoryCache.addToMemory(imaUrl, bitmap);
} else {//否则从网络上下载
Log.d("ImageLoad", "从网络上下载");

HttpURLConnection connection;
URL url;
try {
url = new URL(imaUrl);
connection = (HttpURLConnection) url.openConnection();
connection.setReadTimeout(3000);
connection.setDoInput(true);
connection.setRequestMethod("GET");
connection.connect();
if (connection.getResponseCode() == 200) {
/* 同一个stream只能读取一次
InputStream inputStream = connection.getInputStream();
final Bitmap bitmap = BitmapFactory.decodeStream(connection.getInputStream());
if (mIV.getTag() != null && mIV.getTag().equals(imaUrl)) {
mIV.post(new Runnable() {
@Override
public void run() {
mIV.setImageBitmap(bitmap);
}
});
}

MemoryCache.addToMemory(imaUrl, bitmap);
DiskCache.getInstance().save(imaUrl, connection.getInputStream());*/
DiskCache.getInstance().save(imaUrl, connection.getInputStream());
final Bitmap bitmap = decodeFileToBitmap(DiskCache.getInstance().get(imaUrl));
if (mIV.getTag() != null && mIV.getTag().equals(imaUrl)) {
mIV.post(new Runnable() {
@Override
public void run() {
mIV.setImageBitmap(bitmap);
}
});
}
MemoryCache.addToMemory(imaUrl,bitmap);
connection.disconnect();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
}

}
}

private Bitmap decodeFileToBitmap(File file) {
Bitmap bitmap = BitmapFactory.decodeFile(file.getPath());
return bitmap;
}
}


图片资源  从Universal Image Loader中获取的
package com.example.renlei.myapplication.imageload.myimageload;

import com.example.renlei.myapplication.R;

/**
* Created by renlei
* DATE: 16/6/29
* Time: 15:14
*/
public class ImageUrlConstant {
public static String [] imgUrls = new String[]{
"https://lh6.googleusercontent.com/-55osAWw3x0Q/URquUtcFr5I/AAAAAAAAAbs/rWlj1RUKrYI/s1024/A%252520Photographer.jpg",
"https://lh4.googleusercontent.com/--dq8niRp7W4/URquVgmXvgI/AAAAAAAAAbs/-gnuLQfNnBA/s1024/A%252520Song%252520of%252520Ice%252520and%252520Fire.jpg",
"https://lh5.googleusercontent.com/-7qZeDtRKFKc/URquWZT1gOI/AAAAAAAAAbs/hqWgteyNXsg/s1024/Another%252520Rockaway%252520Sunset.jpg",
"https://lh3.googleusercontent.com/--L0Km39l5J8/URquXHGcdNI/AAAAAAAAAbs/3ZrSJNrSomQ/s1024/Antelope%252520Butte.jpg",
"https://lh6.googleusercontent.com/-8HO-4vIFnlw/URquZnsFgtI/AAAAAAAAAbs/WT8jViTF7vw/s1024/Antelope%252520Hallway.jpg",
"https://lh4.googleusercontent.com/-WIuWgVcU3Qw/URqubRVcj4I/AAAAAAAAAbs/YvbwgGjwdIQ/s1024/Antelope%252520Walls.jpg",
"https://lh6.googleusercontent.com/-UBmLbPELvoQ/URqucCdv0kI/AAAAAAAAAbs/IdNhr2VQoQs/s1024/Apre%2525CC%252580s%252520la%252520Pluie.jpg",
"https://lh3.googleusercontent.com/-s-AFpvgSeew/URquc6dF-JI/AAAAAAAAAbs/Mt3xNGRUd68/s1024/Backlit%252520Cloud.jpg",
"https://lh5.googleusercontent.com/-bvmif9a9YOQ/URquea3heHI/AAAAAAAAAbs/rcr6wyeQtAo/s1024/Bee%252520and%252520Flower.jpg",
"https://lh5.googleusercontent.com/-n7mdm7I7FGs/URqueT_BT-I/AAAAAAAAAbs/9MYmXlmpSAo/s1024/Bonzai%252520Rock%252520Sunset.jpg",
"https://lh6.googleusercontent.com/-4CN4X4t0M1k/URqufPozWzI/AAAAAAAAAbs/8wK41lg1KPs/s1024/Caterpillar.jpg",
"https://lh3.googleusercontent.com/-rrFnVC8xQEg/URqufdrLBaI/AAAAAAAAAbs/s69WYy_fl1E/s1024/Chess.jpg",
"https://lh5.googleusercontent.com/-WVpRptWH8Yw/URqugh-QmDI/AAAAAAAAAbs/E-MgBgtlUWU/s1024/Chihuly.jpg",
"https://lh5.googleusercontent.com/-0BDXkYmckbo/URquhKFW84I/AAAAAAAAAbs/ogQtHCTk2JQ/s1024/Closed%252520Door.jpg",
"https://lh3.googleusercontent.com/-PyggXXZRykM/URquh-kVvoI/AAAAAAAAAbs/hFtDwhtrHHQ/s1024/Colorado%252520River%252520Sunset.jpg",
"https://lh3.googleusercontent.com/-ZAs4dNZtALc/URquikvOCWI/AAAAAAAAAbs/DXz4h3dll1Y/s1024/Colors%252520of%252520Autumn.jpg",
"https://lh4.googleusercontent.com/-GztnWEIiMz8/URqukVCU7bI/AAAAAAAAAbs/jo2Hjv6MZ6M/s1024/Countryside.jpg",
"https://lh4.googleusercontent.com/-bEg9EZ9QoiM/URquklz3FGI/AAAAAAAAAbs/UUuv8Ac2BaE/s1024/Death%252520Valley%252520-%252520Dunes.jpg",
"https://lh6.googleusercontent.com/-ijQJ8W68tEE/URqulGkvFEI/AAAAAAAAAbs/zPXvIwi_rFw/s1024/Delicate%252520Arch.jpg",
"https://lh5.googleusercontent.com/-Oh8mMy2ieng/URqullDwehI/AAAAAAAAAbs/TbdeEfsaIZY/s1024/Despair.jpg",
"https://lh5.googleusercontent.com/-gl0y4UiAOlk/URqumC_KjBI/AAAAAAAAAbs/PM1eT7dn4oo/s1024/Eagle%252520Fall%252520Sunrise.jpg",
"https://lh3.googleusercontent.com/-hYYHd2_vXPQ/URqumtJa9eI/AAAAAAAAAbs/wAalXVkbSh0/s1024/Electric%252520Storm.jpg",
"https://lh5.googleusercontent.com/-PyY_yiyjPTo/URqunUOhHFI/AAAAAAAAAbs/azZoULNuJXc/s1024/False%252520Kiva.jpg",
"https://lh6.googleusercontent.com/-PYvLVdvXywk/URqunwd8hfI/AAAAAAAAAbs/qiMwgkFvf6I/s1024/Fitzgerald%252520Streaks.jpg",
"https://lh4.googleusercontent.com/-KIR_UobIIqY/URquoCZ9SlI/AAAAAAAAAbs/Y4d4q8sXu4c/s1024/Foggy%252520Sunset.jpg",
"https://lh6.googleusercontent.com/-9lzOk_OWZH0/URquoo4xYoI/AAAAAAAAAbs/AwgzHtNVCwU/s1024/Frantic.jpg",
"https://lh3.googleusercontent.com/-0X3JNaKaz48/URqupH78wpI/AAAAAAAAAbs/lHXxu_zbH8s/s1024/Golden%252520Gate%252520Afternoon.jpg",
"https://lh6.googleusercontent.com/-95sb5ag7ABc/URqupl95RDI/AAAAAAAAAbs/g73R20iVTRA/s1024/Golden%252520Gate%252520Fog.jpg",
"https://lh3.googleusercontent.com/-JB9v6rtgHhk/URqup21F-zI/AAAAAAAAAbs/64Fb8qMZWXk/s1024/Golden%252520Grass.jpg",
"https://lh4.googleusercontent.com/-EIBGfnuLtII/URquqVHwaRI/AAAAAAAAAbs/FA4McV2u8VE/s1024/Grand%252520Teton.jpg",
"https://lh4.googleusercontent.com/-WoMxZvmN9nY/URquq1v2AoI/AAAAAAAAAbs/grj5uMhL6NA/s1024/Grass%252520Closeup.jpg",
"https://lh3.googleusercontent.com/-6hZiEHXx64Q/URqurxvNdqI/AAAAAAAAAbs/kWMXM3o5OVI/s1024/Green%252520Grass.jpg",
"https://lh5.googleusercontent.com/-6LVb9OXtQ60/URquteBFuKI/AAAAAAAAAbs/4F4kRgecwFs/s1024/Hanging%252520Leaf.jpg",
"https://lh4.googleusercontent.com/-zAvf__52ONk/URqutT_IuxI/AAAAAAAAAbs/D_bcuc0thoU/s1024/Highway%2525201.jpg",
"https://lh6.googleusercontent.com/-H4SrUg615rA/URquuL27fXI/AAAAAAAAAbs/4aEqJfiMsOU/s1024/Horseshoe%252520Bend%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-JhFi4fb_Pqw/URquuX-QXbI/AAAAAAAAAbs/IXpYUxuweYM/s1024/Horseshoe%252520Bend.jpg",
"https://lh5.googleusercontent.com/-UGgssvFRJ7g/URquueyJzGI/AAAAAAAAAbs/yYIBlLT0toM/s1024/Into%252520the%252520Blue.jpg",
"https://lh3.googleusercontent.com/-CH7KoupI7uI/URquu0FF__I/AAAAAAAAAbs/R7GDmI7v_G0/s1024/Jelly%252520Fish%2525202.jpg",
"https://lh4.googleusercontent.com/-pwuuw6yhg8U/URquvPxR3FI/AAAAAAAAAbs/VNGk6f-tsGE/s1024/Jelly%252520Fish%2525203.jpg",
"https://lh5.googleusercontent.com/-GoUQVw1fnFw/URquv6xbC0I/AAAAAAAAAbs/zEUVTQQ43Zc/s1024/Kauai.jpg",
"https://lh6.googleusercontent.com/-8QdYYQEpYjw/URquwvdh88I/AAAAAAAAAbs/cktDy-ysfHo/s1024/Kyoto%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-vPeekyDjOE0/URquwzJ28qI/AAAAAAAAAbs/qxcyXULsZrg/s1024/Lake%252520Tahoe%252520Colors.jpg",
"https://lh4.googleusercontent.com/-xBPxWpD4yxU/URquxWHk8AI/AAAAAAAAAbs/ARDPeDYPiMY/s1024/Lava%252520from%252520the%252520Sky.jpg",
"https://lh3.googleusercontent.com/-897VXrJB6RE/URquxxxd-5I/AAAAAAAAAbs/j-Cz4T4YvIw/s1024/Leica%25252050mm%252520Summilux.jpg",
"https://lh5.googleusercontent.com/-qSJ4D4iXzGo/URquyDWiJ1I/AAAAAAAAAbs/k2pBXeWehOA/s1024/Leica%25252050mm%252520Summilux.jpg",
"https://lh6.googleusercontent.com/-dwlPg83vzLg/URquylTVuFI/AAAAAAAAAbs/G6SyQ8b4YsI/s1024/Leica%252520M8%252520%252528Front%252529.jpg",
"https://lh3.googleusercontent.com/-R3_EYAyJvfk/URquzQBv8eI/AAAAAAAAAbs/b9xhpUM3pEI/s1024/Light%252520to%252520Sand.jpg",
"https://lh3.googleusercontent.com/-fHY5h67QPi0/URqu0Cp4J1I/AAAAAAAAAbs/0lG6m94Z6vM/s1024/Little%252520Bit%252520of%252520Paradise.jpg",
"https://lh5.googleusercontent.com/-TzF_LwrCnRM/URqu0RddPOI/AAAAAAAAAbs/gaj2dLiuX0s/s1024/Lone%252520Pine%252520Sunset.jpg",
"https://lh3.googleusercontent.com/-4HdpJ4_DXU4/URqu046dJ9I/AAAAAAAAAbs/eBOodtk2_uk/s1024/Lonely%252520Rock.jpg",
"https://lh6.googleusercontent.com/-erbF--z-W4s/URqu1ajSLkI/AAAAAAAAAbs/xjDCDO1INzM/s1024/Longue%252520Vue.jpg",
"https://lh6.googleusercontent.com/-0CXJRdJaqvc/URqu1opNZNI/AAAAAAAAAbs/PFB2oPUU7Lk/s1024/Look%252520Me%252520in%252520the%252520Eye.jpg",
"https://lh3.googleusercontent.com/-D_5lNxnDN6g/URqu2Tk7HVI/AAAAAAAAAbs/p0ddca9W__Y/s1024/Lost%252520in%252520a%252520Field.jpg",
"https://lh6.googleusercontent.com/-flsqwMrIk2Q/URqu24PcmjI/AAAAAAAAAbs/5ocIH85XofM/s1024/Marshall%252520Beach%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-Y4lgryEVTmU/URqu28kG3gI/AAAAAAAAAbs/OjXpekqtbJ4/s1024/Mono%252520Lake%252520Blue.jpg",
"https://lh4.googleusercontent.com/-AaHAJPmcGYA/URqu3PIldHI/AAAAAAAAAbs/lcTqk1SIcRs/s1024/Monument%252520Valley%252520Overlook.jpg",
"https://lh4.googleusercontent.com/-vKxfdQ83dQA/URqu31Yq_BI/AAAAAAAAAbs/OUoGk_2AyfM/s1024/Moving%252520Rock.jpg",
"https://lh5.googleusercontent.com/-CG62QiPpWXg/URqu4ia4vRI/AAAAAAAAAbs/0YOdqLAlcAc/s1024/Napali%252520Coast.jpg",
"https://lh6.googleusercontent.com/-wdGrP5PMmJQ/URqu5PZvn7I/AAAAAAAAAbs/m0abEcdPXe4/s1024/One%252520Wheel.jpg",
"https://lh6.googleusercontent.com/-6WS5DoCGuOA/URqu5qx1UgI/AAAAAAAAAbs/giMw2ixPvrY/s1024/Open%252520Sky.jpg",
"https://lh6.googleusercontent.com/-u8EHKj8G8GQ/URqu55sM6yI/AAAAAAAAAbs/lIXX_GlTdmI/s1024/Orange%252520Sunset.jpg",
"https://lh6.googleusercontent.com/-74Z5qj4bTDE/URqu6LSrJrI/AAAAAAAAAbs/XzmVkw90szQ/s1024/Orchid.jpg",
"https://lh6.googleusercontent.com/-lEQE4h6TePE/URqu6t_lSkI/AAAAAAAAAbs/zvGYKOea_qY/s1024/Over%252520there.jpg",
"https://lh5.googleusercontent.com/-cauH-53JH2M/URqu66v_USI/AAAAAAAAAbs/EucwwqclfKQ/s1024/Plumes.jpg",
"https://lh3.googleusercontent.com/-eDLT2jHDoy4/URqu7axzkAI/AAAAAAAAAbs/iVZE-xJ7lZs/s1024/Rainbokeh.jpg",
"https://lh5.googleusercontent.com/-j1NLqEFIyco/URqu8L1CGcI/AAAAAAAAAbs/aqZkgX66zlI/s1024/Rainbow.jpg",
"https://lh5.googleusercontent.com/-DRnqmK0t4VU/URqu8XYN9yI/AAAAAAAAAbs/LgvF_592WLU/s1024/Rice%252520Fields.jpg",
"https://lh3.googleusercontent.com/-hwh1v3EOGcQ/URqu8qOaKwI/AAAAAAAAAbs/IljRJRnbJGw/s1024/Rockaway%252520Fire%252520Sky.jpg",
"https://lh5.googleusercontent.com/-wjV6FQk7tlk/URqu9jCQ8sI/AAAAAAAAAbs/RyYUpdo-c9o/s1024/Rockaway%252520Flow.jpg",
"https://lh6.googleusercontent.com/-6cAXNfo7D20/URqu-BdzgPI/AAAAAAAAAbs/OmsYllzJqwo/s1024/Rockaway%252520Sunset%252520Sky.jpg",
"https://lh3.googleusercontent.com/-sl8fpGPS-RE/URqu_BOkfgI/AAAAAAAAAbs/Dg2Fv-JxOeg/s1024/Russian%252520Ridge%252520Sunset.jpg",
"https://lh6.googleusercontent.com/-gVtY36mMBIg/URqu_q91lkI/AAAAAAAAAbs/3CiFMBcy5MA/s1024/Rust%252520Knot.jpg",
"https://lh6.googleusercontent.com/-GHeImuHqJBE/URqu_FKfVLI/AAAAAAAAAbs/axuEJeqam7Q/s1024/Sailing%252520Stones.jpg",
"https://lh3.googleusercontent.com/-hBbYZjTOwGc/URqu_ycpIrI/AAAAAAAAAbs/nAdJUXnGJYE/s1024/Seahorse.jpg",
"https://lh3.googleusercontent.com/-Iwi6-i6IexY/URqvAYZHsVI/AAAAAAAAAbs/5ETWl4qXsFE/s1024/Shinjuku%252520Street.jpg",
"https://lh6.googleusercontent.com/-amhnySTM_MY/URqvAlb5KoI/AAAAAAAAAbs/pFCFgzlKsn0/s1024/Sierra%252520Heavens.jpg",
"https://lh5.googleusercontent.com/-dJgjepFrYSo/URqvBVJZrAI/AAAAAAAAAbs/v-F5QWpYO6s/s1024/Sierra%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-Z4zGiC5nWdc/URqvBdEwivI/AAAAAAAAAbs/ZRZR1VJ84QA/s1024/Sin%252520Lights.jpg",
"https://lh4.googleusercontent.com/-_0cYiWW8ccY/URqvBz3iM4I/AAAAAAAAAbs/9N_Wq8MhLTY/s1024/Starry%252520Lake.jpg",
"https://lh3.googleusercontent.com/-A9LMoRyuQUA/URqvCYx_JoI/AAAAAAAAAbs/s7sde1Bz9cI/s1024/Starry%252520Night.jpg",
"https://lh3.googleusercontent.com/-KtLJ3k858eY/URqvC_2h_bI/AAAAAAAAAbs/zzEBImwDA_g/s1024/Stream.jpg",
"https://lh5.googleusercontent.com/-dFB7Lad6RcA/URqvDUftwWI/AAAAAAAAAbs/BrhoUtXTN7o/s1024/Strip%252520Sunset.jpg",
"https://lh5.googleusercontent.com/-at6apgFiN20/URqvDyffUZI/AAAAAAAAAbs/clABCx171bE/s1024/Sunset%252520Hills.jpg",
"https://lh4.googleusercontent.com/-7-EHhtQthII/URqvEYTk4vI/AAAAAAAAAbs/QSJZoB3YjVg/s1024/Tenaya%252520Lake%2525202.jpg",
"https://lh6.googleusercontent.com/-8MrjV_a-Pok/URqvFC5repI/AAAAAAAAAbs/9inKTg9fbCE/s1024/Tenaya%252520Lake.jpg",
"https://lh5.googleusercontent.com/-B1HW-z4zwao/URqvFWYRwUI/AAAAAAAAAbs/8Peli53Bs8I/s1024/The%252520Cave%252520BW.jpg",
"https://lh3.googleusercontent.com/-PO4E-xZKAnQ/URqvGRqjYkI/AAAAAAAAAbs/42nyADFsXag/s1024/The%252520Fisherman.jpg",
"https://lh4.googleusercontent.com/-iLyZlzfdy7s/URqvG0YScdI/AAAAAAAAAbs/1J9eDKmkXtk/s1024/The%252520Night%252520is%252520Coming.jpg",
"https://lh6.googleusercontent.com/-G-k7YkkUco0/URqvHhah6fI/AAAAAAAAAbs/_taQQG7t0vo/s1024/The%252520Road.jpg",
"https://lh6.googleusercontent.com/-h-ALJt7kSus/URqvIThqYfI/AAAAAAAAAbs/ejiv35olWS8/s1024/Tokyo%252520Heights.jpg",
"https://lh5.googleusercontent.com/-Hy9k-TbS7xg/URqvIjQMOxI/AAAAAAAAAbs/RSpmmOATSkg/s1024/Tokyo%252520Highway.jpg",
"https://lh6.googleusercontent.com/-83oOvMb4OZs/URqvJL0T7lI/AAAAAAAAAbs/c5TECZ6RONM/s1024/Tokyo%252520Smog.jpg",
"https://lh3.googleusercontent.com/-FB-jfgREEfI/URqvJI3EXAI/AAAAAAAAAbs/XfyweiRF4v8/s1024/Tufa%252520at%252520Night.jpg",
"https://lh4.googleusercontent.com/-vngKD5Z1U8w/URqvJUCEgPI/AAAAAAAAAbs/ulxCMVcU6EU/s1024/Valley%252520Sunset.jpg",
"https://lh6.googleusercontent.com/-DOz5I2E2oMQ/URqvKMND1kI/AAAAAAAAAbs/Iqf0IsInleo/s1024/Windmill%252520Sunrise.jpg",
"https://lh5.googleusercontent.com/-biyiyWcJ9MU/URqvKculiAI/AAAAAAAAAbs/jyPsCplJOpE/s1024/Windmill.jpg",
"https://lh4.googleusercontent.com/-PDT167_xRdA/URqvK36mLcI/AAAAAAAAAbs/oi2ik9QseMI/s1024/Windmills.jpg",
"https://lh5.googleusercontent.com/-kI_QdYx7VlU/URqvLXCB6gI/AAAAAAAAAbs/N31vlZ6u89o/s1024/Yet%252520Another%252520Rockaway%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-e9NHZ5k5MSs/URqvMIBZjtI/AAAAAAAAAbs/1fV810rDNfQ/s1024/Yosemite%252520Tree.jpg",
// Light images
"http://tabletpcssource.com/wp-content/uploads/2011/05/android-logo.png",
"http://simpozia.com/pages/images/stories/windows-icon.png",
"http://radiotray.sourceforge.net/radio.png",
"http://www.bandwidthblog.com/wp-content/uploads/2011/11/twitter-logo.png",
"http://weloveicons.s3.amazonaws.com/icons/100907_itunes1.png",
"http://weloveicons.s3.amazonaws.com/icons/100929_applications.png",
"http://www.idyllicmusic.com/index_files/get_apple-iphone.png",
"http://www.frenchrevolutionfood.com/wp-content/uploads/2009/04/Twitter-Bird.png",
"http://3.bp.blogspot.com/-ka5MiRGJ_S4/TdD9OoF6bmI/AAAAAAAAE8k/7ydKtptUtSg/s1600/Google_Sky%2BMaps_Android.png",
"http://www.desiredsoft.com/images/icon_webhosting.png",
"http://goodereader.com/apps/wp-content/uploads/downloads/thumbnails/2012/01/hi-256-0-99dda8c730196ab93c67f0659d5b8489abdeb977.png",
"http://1.bp.blogspot.com/-mlaJ4p_3rBU/TdD9OWxN8II/AAAAAAAAE8U/xyynWwr3_4Q/s1600/antivitus_free.png",
"http://cdn3.iconfinder.com/data/icons/transformers/computer.png",
"http://cdn.geekwire.com/wp-content/uploads/2011/04/firefox.png?7794fe",
"https://ssl.gstatic.com/android/market/com.rovio.angrybirdsseasons/hi-256-9-347dae230614238a639d21508ae492302340b2ba",
"http://androidblaze.com/wp-content/uploads/2011/12/tablet-pc-256x256.jpg",
"http://www.theblaze.com/wp-content/uploads/2011/08/Apple.png",
"http://1.bp.blogspot.com/-y-HQwQ4Kuu0/TdD9_iKIY7I/AAAAAAAAE88/3G4xiclDZD0/s1600/Twitter_Android.png",
"http://3.bp.blogspot.com/-nAf4IMJGpc8/TdD9OGNUHHI/AAAAAAAAE8E/VM9yU_lIgZ4/s1600/Adobe%2BReader_Android.png",
"http://cdn.geekwire.com/wp-content/uploads/2011/05/oovoo-android.png?7794fe",
"http://icons.iconarchive.com/icons/kocco/ndroid/128/android-market-2-icon.png",
"http://thecustomizewindows.com/wp-content/uploads/2011/11/Nicest-Android-Live-Wallpapers.png",
"http://c.wrzuta.pl/wm16596/a32f1a47002ab3a949afeb4f",
"http://macprovid.vo.llnwd.net/o43/hub/media/1090/6882/01_headline_Muse.jpg",
// Special cases
"http://cdn.urbanislandz.com/wp-content/uploads/2011/10/MMSposter-large.jpg", // Very large image
"http://www.ioncannon.net/wp-content/uploads/2011/06/test9.webp", // WebP image
"http://4.bp.blogspot.com/-LEvwF87bbyU/Uicaskm-g6I/AAAAAAAAZ2c/V-WZZAvFg5I/s800/Pesto+Guacamole+500w+0268.jpg", // Image with "Mark has been invalidated" problem
"file:///sdcard/Universal Image Loader @#&=+-_.,!()~'%20.png", // Image from SD card with encoded symbols
"assets://Living Things @#&=+-_.,!()~'%20.jpg", // Image from assets
"drawable://" + R.mipmap.ic_launcher, // Image from drawables
"http://upload.wikimedia.org/wikipedia/ru/b/b6/Как_кот_с_мышами_воевал.png", // Link with UTF-8
"https://www.eff.org/sites/default/files/chrome150_0.jpg", // Image from HTTPS
"http://bit.ly/soBiXr", // Redirect link
"http://img001.us.expono.com/100001/100001-1bc30-2d736f_m.jpg", // EXIF
"", // Empty link
"http://wrong.site.com/corruptedLink", // Wrong link
};
}


参考资料
http://www.cnblogs.com/kissazi2/p/3931400.html
Android 三大缓存图片原理，特性对比  http://www.trinea.cn/android/android-image-cache-compare/