Android requires that all applications be packaged up into an apk and signed with a digital certificate before it will consider running them. This is true for the emulator and for your personal testing devices, but it’s especially true for programs that you want to publish on the Play Store.

“But wait,” you say, “I haven’t been packaging or signing anything up to now.” Actually, you have. The Android SDK tools have been secretly building and signing everything using a certificate that Google created using a known alias and password. Because the password was known, you were never prompted for it and probably never even knew it existed. However, the debug certificate can’t be used for applications in the Play Store, so now it’s time to ...

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