how to start development of android applications? [closed]

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http://stackoverflow.com – Since I have a requirement to develop a application. The application must do the following The application must be able to send SMS. It should be able to save messages as drafts SMS. It should also save messages as templates. No limits should be there for saving templates and drafts. It should show contacts when send action is clicked. Please help from where should I start. I have experience only .net Mobile application. (HowTos)