Defines the persistence of the drawing cache. The drawing cache might be enabled by a ViewGroup for all its children in specific situations (for instance during a scrolling.) This property lets you persist the cache in memory after its initial usage. Persisting the cache consumes more memory but may prevent frequent garbage collection is the cache is created over and over again. By default the persistence is set to scrolling.
大致意思如下：
定義繪圖的高速緩存的持久性。 繪圖緩存可能由一個 ViewGroup 在特定情況下爲其所有的子類啓用，例如在一個滾動的過程中。 此屬性可以保留在內存中的緩存後其初始的使用。 堅持緩存會消耗更多的內存，但可能會阻止頻繁的垃圾回收是反覆創建緩存。 默認情況下持續存在設置爲滾動。
其屬性值只有以下幾種：
Constant Value Description
none 0x0 The drawing cache is not persisted after use.
animation 0x1 The drawing cache is persisted after a layout animation.
scrolling 0x2 The drawing cache is persisted after a scroll.
all 0x3 The drawing cache is always persisted.