The two spreadsheet api are: google-apps-script and google-spreadsheet-api ...
Google apps script has good docs and is of good quality, but I suspect google-spreadsheet-api will be a better fit for android development, but depends on your needs.
The google CellDemo.java demo gives a good overview of the spreadsheet api. https://code.google.com/p/gdata-java-client/source/browse/trunk/java/sample/spreadsheet/cell/CellDemo.java
There is also ethercalc - it is a web based spreadsheet, good quality, all open source.