Signing Application Before Publishing on Play Store

To sign app we need to perform following 4 tasks.

1.   Obtain a suitable private key
2.  Compile the application in release mode
3.  Sign your application with your private key
4.  Align the final APK package

We perform these tasks by following given steps:

Step 1: Right click on the Android project. From the context menu, select, Android Tools -> Export Unsigned application package. Browse to the location you want your unsigned  apk  file to save and then click on SAVE.

Step 2:   Generating Certificate, keystore and signing app with private key.

If you have Keytool (installed in eclipse)  then all the three works can be done  in a single step.

To install the plugin in Eclipse Follow the following steps:

1.     Go to Option: Help – Install New Software .

2.     Type “http://keytool.sourceforge.net/update” in Work with:  text-area.

3.     Check the box Keytool and hit Finish button.

If Keytool checkbox does not appear then click add button and type http://keytool.sourceforge.net/update in Location Field of  Add Repository dialog box. In Name field type anything.

If Keytool is installed properly then your ecplipse will have such icon on tool bar:

 If you don't have a keystore(certificate for app) already, you will need to create one first. Once created, you should preserve this keystore somewhere, safely, so that you don't accidentally delete it. You will need this keystore everytime you want to sign and update your application to the Android Market. Please,  DO NOT LOSE THIS KEYSTORE.

When you’ll create it first time, a dialog box will pop-up as shown below. Just click “ok” and proceed.

Enter all the fields in this screen and press “Next”. Now your keystore will is created. Please remember all your passwords. Else, this keystore will be useless for you later.

NOTE: Alias name could be anything but better if you keep it as your app’s name for your convenience.

Browse to the location where your unsigned apk  file is saved. Enter Keystore password. For simplicity, keep both the passwords same. Click Finish. Your certificate is generated and your apk file is also signed after this 

                                        

Certificate will be generated like this:

Step 3:   Right click on the Android project. From the context menu, select, Android Tools -> Export Signed application package. In the dialog that will open, you will see the name of your project. If you have selected the wrong project, here is a chance to correct yourself. Click on "Next".

Step 4:  now perform Zipalign on your signed apk.

The zipalign tool is provided with the Android SDK, inside the tools/ directory. To align your signed APK, execute:

$ zipalign -v 4 your_project_name-unaligned.apk your_project_name.apk

The -v flag turns on verbose output (optional). 4 is the byte-alignment (don't use anything other than 4). The first file argument is your signed .apk file (the input) and the second file is the destination .apk file (the output). If you're overriding an existing APK, add the -f flag.

 You can download  Zipalign tool  and perform zipalign on your apk. Now your app is ready to upload apk on play store.

Caution: Your input APK must be signed with your private key before you optimize the package with zipalign. If you sign it after using zipalign, it will undo the alignment.