How to get signed apk for flutter with existing app keystore?

Edit the AndroidManifest according to your needs then add in android/key.properties the keystore data:

storePassword=STORE_PASSWORD
keyPassword=KRY_PASSWORD
keyAlias=ALIAS
storeFile=..\\android.jks

then place your *.jks (in this case android.jks) in android/

In your app/build.gradle add those lines:

def keystorePropertiesFile = rootProject.file("key.properties")
def keystoreProperties = new Properties()
keystoreProperties.load(new FileInputStream(keystorePropertiesFile))

When you build your flutter app with flutter build apk a release apk with the given keystore will be generated in build/app/outputs/apk/release/app-release.apk.

If you generated previous fresh Signed APK using Android Studio as steps given in bellow link then don't worry.

For more info check this link

stackoverflow.com/questions/55536637/how-to-build-signed-apk-from-android-studio-for-flutter/60163484#60163484

Now just follow the following steps to build signed apk with existing keystore details.

IMPORTANT

Before generating Signed APK with existing keystore details make sure upgrade each time your Flutter Version from pubspec.yaml file and Version Code from local.properties file.

For example

If previous flutter version code in pubspec.yaml file is

version: 1.0.0+1 then change it or upgrade it to the version: 1.0.0+2 or any other greater number than previous after + sign.

And if flutter.versionCode in Project -> android -> local.properties is

flutter.versionCode=1 then change it or upgrade it to the flutter.versionCode=2 or any other greater number than previous code. [This Version Code is important while releasing your app on Google Play Console with existing app i.e. for release New Update]

After that follow the steps bellow -

Step 1:

Go to in your project & then Tools -> Flutter -> Open for Editing in Android Studio as shown below

Then Select New Window option as shown below

Step 2 :

Wait for while until project synchronization. After that Go to Build -> GenerateSigned Bundle/APK... option from menu bar as shown bellow

Step 3 :

Select Android App Bundle or APK Option as per your need. (Android App Bundle is best solution) and click Next button.

Step 4 :

Select Choose existing... option to generate Signed APK with existing keystore details. (When you upload flutter app in place of existing application with same package.)

Select Key store path where your key store file .jks file stored. [The path within your project directory.] (as mentioned above link)]

Then fill the all options i.e.

Key store password

Key alias

Key Password

and Click Next button as shown bellow...

Step 5 :

Select options

Build variants - release and

Signature versions both V1 and V2 respectively as shown above screen shot and click Finish button as shown bellow.

Step 8 :

Wait for a while until Gradle Build Running process.

and finally you will get the Generate Signed APK : (APKs) generated successfully. from that click on Locate option to get Location of your Generate Signed APK File. as shown bellow.

That's it you generated Signed APK successfully for update your flutter app in place of existing application with same package.