There are some references about tutorials, examples and source code. Reading it by order will give you some confidence.
1 Make your first Android App: http://www.raywenderlich.com/56109/make-first-android-app-part-1
2 Build an application in 6 steps: http://coenraets.org/blog/androidtutorial/
My Map Location http://joshclemm.com/blog/?p=148
Very useful for checking the map: http://android-er.blogspot.ca/2012/12/a-simple-example-using-google-maps.html
5 Android Code Path http://guides.codepath.com/android/#structure
6 Refer from (stackoverflow) All of the applications delivered with Android (Calendar, Contacts, Email, etc) are all open-source, but not part of the SDK. The source for those projects is here: https://android.googlesource.com/ (look at /platform/packages/apps). I’ve referred to those sources several times when I’ve used an application on my phone and wanted to see how a particular feature was implemented.
7 Android examples: http://androidexample.com/
How to use the sample code in Android http://code.tutsplus.com/tutorials/android-sample-apps–mobile-12528
8 Exampes classified by different categories http://www.java2s.com/Code/Android/CatalogAndroid.htm
9 Android developer website (http://developer.android.com/)