[Android Studio](https://developer.android.com/sdk/installing/studio.html) is the recommended development environment.
1. Install Android Studio
2. Make sure the "Android Support Repository" is installed in the Android Studio SDK.
3. Make sure the latest "Android SDK build-tools" is installed in the Android Studio SDK.
4. Create a new Android Studio project. from the Quickstart pannel (use File > Close Project to see it), choose "Checkout from Version Control" then "git".
5. Paste the URL for the TextSecure project when prompted (https://github.com/WhisperSystems/TextSecure.git)
6. Android studio should detect the presence of a project file and ask you wethere to open it. Click "yes".
7. Default config options should be good enough.
8. Project initialisation and build should proceed.
Contributing code
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Code contributions should be sent via github as pull requests, from feature branches [as explained here](https://help.github.com/articles/using-pull-requests).
Mailing list
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Development discussion happens on the whispersystems mailing list.