Android Programming: The Big Nerd Ranch Guide

Challenge: Preloading and Caching

Users accept that not everything can be instantaneous. (Well, most users.) Even so, programmers strive towards perfection.

To approach instantaneity, most real world apps augment the code you have here in two ways:

• adding a caching layer

• preloading images

A cache is a place to stash a certain number of Bitmap objects so that they stick around even when you are done using them. A cache can only hold so many items, so you need a strategy to decide what to keep when your cache runs out of room. Many caches use a strategy called LRU, or “least recently used.” When you are out of room, the cache gets rid of the least recently-used item.

The Android support library has a class called LruCache that implements an LRU ...