如何根据设备选择合适的抽屉

I have been working on few Android apps, but I still don't get the drawable folders. My apps always use only one of the 4 drawables for all sizes in stead of using the appropriate one. For my current project, I created images that I scaled to 92x92, 72x72, 48x48 and 32x32 how can I tell my app to choose from these depending on the device that is used? I have been working on few Android apps, but I