Calculate the sunlight direction according to the current time and position on the earth

How can I calculate the position of the sun according to the current time and position on the earth? I am currently adding light-sources to an Augmented Reality framework on Android and it would be great to know 开发者_JAVA百科where to set the "sun". I think there are a lot of factors but an approximation would be enough for now I think.

take a look at the noaa site, they give you a spreadsheet that gives you the results you want.