Invalid file name error in Eclipse

I often encounter the following error:

res\drawable\my-image-48.png: Invalid file name: must contain only [a-z0-9_.]

My file name is "my-image-48.png" w开发者_C百科hich seems to conform to the constraints listed in the error.

What am I missing?

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you cannot use the dash -, you only can use letters (from a to z), numbers (0 from 9) and underscores _ So you should replace "-" by underscores.

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You can't use - .

[a-z0-9_.] means not you can use -, but that you can use letters from a to z and numbers form 0 to 9 and underscores. Therefore I recommend to substitute - with _

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The dash is not authorized in file names.