In the last two days, I've seen some dozens of tutorials on these aspects, the best of which is the original Google tutorial. There are many articles in China that are translated by this link.
It is important to note that the LRU algorithm in the SDK for Android has one of the V4 packages and the Util package, which is recommended for use in the V4 package.
Here, two links are recommended:
Https://developer.android.com/intl/ru/training/displaying-bitmaps/process-bitmap.html
Http://android-developers.blogspot.jp/2010/07/multithreading-for-performance.html
The second link is a demonstration of the content of the first link, I have clone to my GitHub, and read the content will be more profound understanding, welcome to download.
Https://github.com/freedomofme/android-imagedownloader
Recommended links for Android image compression, and LRU algorithm use