Error when building signed apk for flutter (malformed)

Question

I am getting this error in the terminal, I am looking to release the app in internal testing mode on play store, when i was building it in degub mode it was fine, but play store doesn't accept releases in debug mode, so I change configuration and signed the app to build in release mode

PS C:\Users\Ahmed\mobile-app> flutter build apk

Building without sound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety

                                                                        
FAILURE: Build failed with an exception.                                
                                                                        
* Where:                                                                
Build file 'C:\Users\Ahmed\mobile-app\android\app\build.gradle' line: 31
                                                                        
* What went wrong:                                                      
A problem occurred evaluating project ':app'.                           
> Malformed \uxxxx encoding.                                            
                                                                        
* Try:                                                                  
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
                                                                        
* Get more help at https://help.gradle.org                              
                                                                        
BUILD FAILED in 2s                                                      
Running Gradle task 'assembleRelease'...                                
Running Gradle task 'assembleRelease'... Done                       3.5s
Gradle task assembleRelease failed with exit code 1

This is my build.gradle file

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '2'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0.2'
}

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
    compileSdkVersion 30

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.mylo.donation_yoga"
        minSdkVersion 29
        targetSdkVersion 30
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }

    signingConfigs {
        release {
            keyAlias keystoreProperties['keyAlias']
            keyPassword keystoreProperties['keyPassword']
            storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
            storePassword keystoreProperties['storePassword']
        }
    }
    buildTypes {
        release {
            signingConfig signingConfigs.release
        }
    }

}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

Answer 1

I think something is wrong with your "keystorePropertiesFile". You need to check the file path of the Keystore file in it.

For Example, Replace all the backslash with the forward-slash and it should work because as you told the problem comes only when you do the release so it has to be something wrong in the "keystorePropertiesFile".