Android 三大图片缓存原理、特性对比
http://www.trinea.cn/android/android-image-cache-compare/
http://blog.csdn.net/guolin_blog/article/details/10470797
http://blog.csdn.net/guolin_blog/article/details/46361889
http://www.codeceo.com/article/android-disklrucache.html