I have moved pictures to drawable folder:
But when I tried to use one of the as the background picture, I can’t find some of them:
The reason is:
Please Note the image name can only include lowercase a-z, 0-9, or underscore, otherwise there will have an error when you rebuild the android project. The error message like ” Error: ‘-‘ is not a valid file-based resource name character: File-based resource names must contain only lowercase a-z, 0-9, or underscore ”