Once you publish your application in the Google Play Store, other people will now be depending upon you to fix bugs and otherwise maintain your application. It is therefore very important that you backup your application's source code. To do this, click on "Project-->My Projects", check the box next to the name of your project and then select "Project-->Export selected project (.aia) to my computer." This will download a zip file which contains your projects source code. Store it in a safe place!
TVMC Apk
MIT and Google, which operate the App Engine service on which MIT App Inventor relies, make best efforts to ensure that MIT App Inventor does not lose projects. HOWEVER WE CAN OFFER NO GUARANTEE THAT DATA (LIKE YOUR PROJECTS) WILL NEVER BE LOST. IT IS IMPERATIVE THAT YOU MAKE YOUR OWN BACKUPS!
TeamSpeak 3 Apk
A Word about keystores:
During the .apk building process your application is signed with a digital private key which is associated with your account. Whenever you build a new version this same key is used to sign the new version. When an android phone has an application installed on it, it remembers the key that was used to sign it. In order to install an updated version of an application, the new application must be signed by the same key. It is therefore important that you not lose this key!
Your private digital key is stored in a keystore file. Normally the MIT App Inventor server will create this file when needed and store it for you so you do not need to worry about it. Although we do not anticipate losing your keystore file, we recommend that you back it up. From the designer under the "Projects" menu there is a choice labeled "Export Keystore". Select this option. This will download your keystore file to your local computer. Save it in a safe place. It should not be publicly readable as your private digital key is a secret which should not be shared.
If you move your project to another App Inventor server, you will want to upload your keystore to that server (you will see that under "Projects" there is a "Import Keystore" option as well). You only need to do this if you are publishing .apk files to Google Play or if you intend to share your application with other people in general.
IF YOUR keyfile IS LOST OR DELETED IT CANNOT BE RECOVERED. If you were to lose your project's source code, you could always re-enter it from scratch (this may be a lot of work, but is something you can do). NEITHER YOU NOR MIT CAN RECOVER A LOST keyfile. NO AMOUNT OF EFFORT WILL RECOVER IT, SO BE SURE TO BACK IT UP!!!