What is INSTALL_PARSE_FAILED_NO_CERTIFICATES error?

I found that this error can now also occur when using the wrong signing config. As described here, Android 7.0 introduces a new signature scheme, V2. The V2 scheme signs the entire APK rather than just the JAR, as is done in the V1 scheme. If you sign with only V2, and attempt to install on a pre-7.0 target, you'll get this error since the JARs themselves are not signed and the pre-7.0 PackageManager cannot detect the presence of the V2 APK signature.

To be compatible with all target systems, make sure the APK is signed with both schemes by checking both signature version boxes in Android Studio's Generate Signed APK dialog as shown here:

If only 7.0 targets are anticipated, then there is no need to include the V1 signature.

Did you edit the AndroidManifest.xml directly in the .apk file? If so, that won't work.

Every Android .apk needs to be signed if it is going to be installed on a phone, even if you're not installing through the Market. The development tools work round this by signing with a development certificate but the .apk is still signed.

One use of this is so a device can tell if an .apk is a valid upgrade for an installed application, since if it is the Certificates will be the same.

So if you make any changes to your app at all you'll need to rebuild the .apk so it gets signed properly.