How-to: Sign android app

Kian Lee Teo

Intro

Android requires that all apps be digitally signed with a certificate before they can be installed, so to distribute your Android application via Google Play store, you'll need to generate a signed release APK.

Steps on signing android app:

Generating a signing key
Setting up gradle variables
Adding signing config to your app's gradle config
Generating the release APK
Testing the release build of your app

Reference: https://facebook.github.io/react-native/docs/signed-apk-android.html

Kian Lee Teo

1. Generating a signing key

Generate a private signing key using keytool @ C:\Program Files\Java\jdkx.x.x_x\bin with validity of 100 years, the syntax are as follow:

$ keytool -genkey -v -keystore {my-release-key.keystore} -alias {my-key-alias} -keyalg RSA -keysize 2048 -validity 36500

Example, company superco to sign an app named superapp,

{my-release-key.keystore} = superco.keystore
{my-key-alias} = superapp

$ keytool -genkey -v -keystore superco.keystore -alias superapp -keyalg RSA -keysize 2048 -validity 36500

Note: A keystore is a binary file that contains a set of private keys, i.e. you can multiple keys in a keystore.

Kian Lee Teo

2. Setting up gradle variables

Edit global gradle properties file ~/.gradle/gradle.properties and add the following:

RELEASE_STORE_FILE=superco.keystore
RELEASE_KEY_ALIAS=superapp
RELEASE_STORE_PASSWORD=*****
RELEASE_KEY_PASSWORD=*****

Notes:

You can place a gradle.properties file in the Gradle user home directory (defined by the GRADLE_USER_HOME environment variable, which if not set, will defaults to USER_HOME/.gradle) or in your project directory.
In windows if your username is wonderwoman, the location of the gradle.properties will be C:/Users/wonderwoman/.gradle/gradle.properties.
Password must not contains: { } [ ] ( ) / \ ' " ` ~ , ; : . < >

Kian Lee Teo

3. Adding signing config to your app's gradle config

Edit android/app/build.gradle, add the signing config:

...
android {
    ...
    defaultConfig { ... }
    signingConfigs {
        release {
            if (project.hasProperty('RELEASE_STORE_FILE')) {
                storeFile file(RELEASE_STORE_FILE)
                storePassword RELEASE_STORE_PASSWORD
                keyAlias RELEASE_KEY_ALIAS
                keyPassword RELEASE_KEY_PASSWORD
            }
        }
    }
    buildTypes {
        release {
            ...
            signingConfig signingConfigs.release
        }
    }
}
...

Kian Lee Teo

4. Generate release apk

$ cd android && ./gradlew --console plain assembleRelease

Output apk @ android/app/build/outputs/apk/app-release.apk

To review the signing report,

$ gradlew signingReport

5. Testing the release build of your app

$ react-native run-android --variant=release

Kian Lee Teo