MissingPluginException(No implementation found for method getAll on channel plugins.flutter.io/shared_preferences) -exist solutions didn't work-

Question

I am building an application which uses these packages

• firebase_core: ^0.5.0
• firebase_analytics: ^5.0.16
• cloud_firestore:
• firebase_messaging: ^7.0.0
• flutter_local_notifications: ^1.4.4+2
• provider: ^4.3.1
• http: ^0.12.2
• reviews_slider: ^1.0.5
• flutter_screenutil: ^2.3.0
• shared_preferences: ^0.5.12
• scroll_to_index: ^1.0.6
• firebase_database: ^4.0.0
• image_picker: ^0.6.7+11
• get: ^3.11.1

and everything is working fine in the debug mode but when I build a release I get that error I have been searching for 3 days and all I found that you need to

flutter clean
pub get/ pub upgrade

and then it works lie a charm. but it doesn't work for me

here is by app/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 = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

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 28

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

    lintOptions {
        disable 'InvalidPackage'
        checkReleaseBuilds false
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.zonedelivery.zonedelivery"
        minSdkVersion 16
        targetSdkVersion 28
        multiDexEnabled true
        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 {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.release
            minifyEnabled true
            useProguard true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        debug {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.release
            minifyEnabled true
            useProguard true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.google.firebase:firebase-firestore-ktx:21.5.0'
    implementation 'com.google.firebase:firebase-messaging:20.2.3'
    implementation 'com.android.support:multidex:1.0.3'
    implementation 'com.google.firebase:firebase-analytics:17.5.0'
}

apply plugin: 'com.google.gms.google-services'

The proguard-rules.pro file

## Flutter wrapper
-keep class io.flutter.app.** { *; }
-keep class io.flutter.plugin.**  { *; }
-keep class io.flutter.util.**  { *; }
-keep class io.flutter.view.**  { *; }
-keep class io.flutter.**  { *; }
-keep class io.flutter.plugins.**  { *; }
-keep class io.flutter.plugins.sharedpreferences**  { *; }
-dontwarn io.flutter.embedding.**

## Gson rules
# Gson uses generic type information stored in a class file when working with fields. Proguard
# removes such information by default, so configure it to keep all of it.
-keepattributes Signature

# For using GSON @Expose annotation
-keepattributes *Annotation*

# Gson specific classes
-dontwarn sun.misc.**
#-keep class com.google.gson.stream.** { *; }

# Prevent proguard from stripping interface information from TypeAdapter, TypeAdapterFactory,
# JsonSerializer, JsonDeserializer instances (so they can be used in @JsonAdapter)
-keep class * extends com.google.gson.TypeAdapter
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer

# Prevent R8 from leaving Data object members always null
-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
}

## flutter_local_notification plugin rules
-keep class com.dexterous.** { *; }

Answer 1

try downgrading get_it version to: get_it: ^3.0.3 then in the command window write: flutter clean then reinstall the app

Answer 2

The problem is shrinking app removes some important code so it has to be solved in the proguard file So I added this line at the bottom of the proguard file

-keepclasseswithmembers class * {*;}

so it keeps all classes and function without removing any code This solution helped me