"Application not installed" after reinstall sometimes

When my app is installed on the Android and I want to update it, if I don't uninstall and then reinstall, sometimes an in开发者_开发百科stall over top of what's there works, sometimes it doesn't. I have no idea how it decides whether to allow the install or not.

There is no error message, it's just that sometimes the result message is "application installed" and sometimes it's "application not installed".

Is there something I have to do to make sure that a new version can be installed on top of the old version so that the preferences will be preserved? They get deleted on an uninstall.

Thanks!

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When if you change your keystore. It could happen. Keep using just one keystore. And in my opinion, if you want to keep your preferences when you update it, you need something else. You can keep the preferences file using external storage. Copy and overwrite. I think it's the best way.