What is the difference between the apk file in the bin folder and the apk file created through the Export option in Eclipse?
For debugging purposes, can I directly use the file in the bin folder? Or is it recommended to always "export" the apk file?
Apk in bin folder is signed with a dummy key used for debugging (Debug Key). Using the export tool, you specify your own unique key (password protected) to identify your Apps. So, for testing and debuging, you can directly use the one in bin folder. But, for publishing, you must use your own key (via the export tool).
When you export using the tool, it does additional steps to package your APK. This includes running Proguard, Zipalign, and signing your app with your own key.
None of these optimization steps are performed on the APK in the bin directory, but if you don't care about this, you can use that one for testing.
You will need to sign your app with your own private key in order to publish it to the Play Market - and make sure to never lose the key, as you need to use the same one every-time you publish.
The one that is in the bin folder is the unsigned version of the APK. This APK cannot be published to the play store as it requires APK to be self signed.
When you export the APK from eclipse you should selected the signed version and it will take you through the necessary steps to create/sign your APK for publishing
来源：https://stackoverflow.com/questions/14709417/what-is-the-difference-between-the-apk-file-in-the-bin-folder-and-the-apk-file-c