[最佳答案] I presume you are trying to change the "outer" backgroud of a Spinner's popup, not the background of Spinner "pupup items". Also, I presume that by popup, you mean a Spinner's dialog mode, where a floating dialog window appears on top of your activity, as opposed to the new dropdown mode. Strategy For a clean, sustainable approach which behaves well across multiple Android platforms and reduces the need for redundancy in the App, I believe it is essential to understand what