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Editorial Team
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Asked: 2026-06-07T20:44:32+00:00

I want to get the same functionality in a script I’m writing as re-sign.jar

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I want to get the same functionality in a script I’m writing as re-sign.jar (a simple app that allows you to resign android apps for testing and debugging).

To do this, I’m following the these instructions: 

Un-­‐zip the apk file
­Delete the META-­‐INF folder
Re-­‐zip the apk file
In Dos prompt /Command prompt
> jarsigner -keystore ~/.android/debug.keystore -storepass android -keypass android ApplicationToTest.apk androiddebugkey
> zipalign 4 ApplicationToTest.apk TempApplicationToTest.apk

Then rename TempApplicationToTest.apk to ApplicationToTest.apk

What kills me is when I get to the ‘jarsigner’ part, I get the error 

jarsigner error: java.lang.NullPointerException

I can run the re-signer.jar fine so I don’t think I’m missing anything, and I have all the permissions to boot. Any suggestions?

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1 Answer

  1. Editorial Team

    Well… Figured that out. When I was zipping the file it put contents of the file a directory down. It was returning null because it couldn’t find the app files (manifest and such). I feel dumb.

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