Cannot install signed apk to device manually, got error "App not installed"

Question

You may be using the android 5.0 or above device.

May be your development version is not uninstalled properly.

Try this,

Just go to the Settings --> Apps --> Click on your App. ---> In App info page at the action bar menu there will be an option called " Uninstall for All users " click that. Your app will be completely uninstalled and now you can try installing the new version with no issue. Hope this will help you

NOTE : This is for lollipop and above. Refer the screenshot attached.

For Current Updated Android Studio 2.3 users this answer is for you as hardly people use eclipse nowadays for Android development as Android studio has huge advancements.

So, Follow this way to create your Signed apk file.

1. Build > Generate Signed apk.
2. Create Keystore path.
3. Put Password, alias, key password.
4. Build type select accordingly(eg to release in playstore use release).
5. Signature Version select both V1 and V2 checkboxes.
6. Finsih.
7. Go to from explorer where you selected for the apk to store and you will see your .apk file name as app-release.apk use it.

selecting Signature Version v1 and v2 both solved the problem for me....try it

The same thing happened to me, as long as I generated my apk from Build> Build APK. I could install and un-install the apk as many times as they were without any problem, but instead if I generated the Build> Generate Signed APK, when I passed the apk to the phone and try to install it, it only allowed me one occasion, the same one that came out the following message:

until then everything was fine if I selected "INSTALL IN ANY WAY", but what happened if I uninstalled the app and wanted to reinstall it (a possible scenario), the following happened:

so I solved the problem by disabling play protect, which I achieved (within Google Play)> Menu> Play Protect> Search for security threats (disable).

"App not installed" shows when an app with same package already installed in same device. just delete your first application which you were using for testing purpose before making it to signed apk. This will work. cheers!

Select both Signature Version v1 and v2 will resolve the issue

v1 scheme

A JAR file can be signed by using the command line jarsigner tool or directly through the java.security API. Every file entry, including non-signature related files in the META-INF directory, will be signed if the JAR file is signed by the jarsigner tool. For every file entry signed in the signed JAR file, an individual manifest entry is created for it as long as it does not already exist in the manifest

V2 scheme

v1 signatures do not protect some parts of the APK, such as ZIP metadata. The APK verifier needs to process lots of untrusted (not yet verified) data structures and then discard data not covered by the signatures. This offers a sizeable attack surface. Moreover, the APK verifier must uncompress all compressed entries, consuming more time and memory. To address these issues, Android 7.0 introduced APK Signature Scheme v2

By default, Android Studio 2.2 and the Android Plugin for Gradle 2.2 sign your app using both APK Signature Scheme v2 and the traditional signing scheme, which uses JAR signing.

It is recommended to use APK Signature Scheme v2 but is not mandatory. please see the details