android project No R file

error R cannot be resolved to a variable, but does not solve the problem does not seem to generate R file
This is not recursive yet
What fix project such methods useless , are not generated R file
expert to answer in detail about how they do it
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a possible program have other errors, a possible reference to the android sdk problem
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Clean little longer compile, If not , it is estimated the layout of your document , value folder below some XML writing is incorrect. Also, take a look Problems following error, from the inside is basically to find Root cause of .
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Clean project, restart Eclispe
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resolved
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for several reasons, share
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ask you how to solve
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I re Instanll the android2.2 an API on the line