Kotlin: Default interface methods are only supported starting with Android N

Question or issue of Kotlin Programming:

I upgraded to android studio 3.1 and I’m getting the following error:

Default interface methods are only supported starting with Android N (--min-api 24): void android.arch.lifecycle.DefaultLifecycleObserver.onCreate(android.arch.lifecycle.LifecycleOwner)
Message{kind=ERROR, text=Default interface methods are only supported starting with Android N (--min-api 24): void android.arch.lifecycle.DefaultLifecycleObserver.onCreate(android.arch.lifecycle.LifecycleOwner), sources=[Unknown source file], tool name=Optional.of(D8)}

Here is my gradle config:

compileSdkVersion 27
//buildToolsVersion '27.0.3'
defaultConfig {
    minSdkVersion 16
    targetSdkVersion 27
     multiDexEnabled true
     //...
   }

As you can see, I am targeting 27 which is already ahead of 24 that it’s complaining about. What exactly should I do to fix this? If I change to 1.8 java, won’t I be missing a lot of customers? Why was I not getting this error before I upgraded Android Studio?

I do not know if this is about the LifecycleObserver class I recently put in, it was in Kotlin and now I changed it to java but still get the same error after cleaning project:

public class LifeCycleAwareObserver implements LifecycleObserver {

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    public void  onAppBackgrounded() {
        AnalyticsUtils.trackStartSession(true);
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    public void onAppForegrounded() {
        AnalyticsUtils.trackStartSession(false);
    }
}

How to trace where the error is coming from so I can fix it?

Here are my version dependencies:

project.ext {
      
        firebase_version = '12.0.0'

        supportlib_version = '27.0.2'

        room_version = '1.0.0'

        espresso_version = '3.0.1'

        archLifecycleVersion = '1.1.1'
    }

How to solve this issue?

Solution no. 1:

As CommonsWare mentioned, for reference add this inside the android {...} closure in the build.gradle for your app module to resolve issue:

android {
...
  compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
...
}

Solution no. 2:

You should use Java 8 to solve this, based on the Android documentation you can do this by

clicking File > Project Structure

and change Source Compatibility and Target Compatibility.

and you can also configure it directly in the app-level build.gradle file:

android {
  ...
  // Configure only for each module that uses Java 8
  // language features (either in its source code or
  // through dependencies).
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

Solution no. 3:

In app-level gradle, you have to write these code:

android {
...
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

They come from JavaVersion.java in Android.

An enumeration of Java versions.
Before 9: http://www.oracle.com/technetwork/java/javase/versioning-naming-139433.html
After 9: http://openjdk.java.net/jeps/223

@canerkaseler

Solution no. 4:

Update your build.gradle(Module:app) add compileOptions block and add JavaVersion.VERSION_1_8

apply plugin: 'com.android.application' android { ................. ......................... compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } }

Solution no. 5:

You can resolve this issue by downgrading Source Compatibility and Target Compatibility Java Version to 1.8 in Latest Android Studio Version 3.4.1

Open Module Settings (Project Structure) Winodw by right clicking on app folder or Command + Down Arrow on Mac
Go to Modules -> Properties
Change Source Compatibility and Target Compatibility Version to 1.8
Click on Apply or OK Thats it. It will solve your issue.

Also you can manually add in build.gradle (Module: app)

android { ... compileOptions { sourceCompatibility = '1.8' targetCompatibility = '1.8' } ... }

Solution no. 6:

apply plugin: 'com.android.application' apply plugin: 'kotlin-android' apply plugin: 'kotlin-android-extensions' android { compileSdkVersion 30 buildToolsVersion "30.0.0" compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } defaultConfig { applicationId "com.example.architecture" minSdkVersion 16 targetSdkVersion 30 versionCode 1 versionName "1.0" testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro' } } } dependencies { implementation 'androidx.room:room-runtime:2.2.5' implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0' annotationProcessor 'androidx.room:room-compiler:2.2.5' def lifecycle_version = "2.2.0" def arch_version = "2.1.0" implementation fileTree(dir: "libs", include: ["*.jar"]) implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" implementation 'androidx.core:core-ktx:1.3.0' implementation 'androidx.appcompat:appcompat:1.1.0' implementation 'androidx.constraintlayout:constraintlayout:1.1.3' testImplementation 'junit:junit:4.12' androidTestImplementation 'androidx.test.ext:junit:1.1.1' androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0' implementation "androidx.lifecycle:lifecycle-viewmodel-savedstate:$lifecycle_version" implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version" implementation "androidx.lifecycle:lifecycle-service:$lifecycle_version" implementation "androidx.lifecycle:lifecycle-process:$lifecycle_version" implementation "androidx.cardview:cardview:1.0.0" }

Add the configuration in your app module’s build.gradle

android { ... compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } }

Solution no. 7:

Use this code in your build.gradle

android { compileOptions { incremental true sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } }

Solution no. 8:

My project use ButterKnife and Retro lambda, setting JavaVersion.VERSION_1_8 will not work. It always blames at ButterKnife static interface function until I found this Migrate from Retrolambda

TL;DR

Just add JavaVersion.VERSION_1_8 and completely REMOVE retrolambda from your project. It will build successfully.

Solution no. 9:

Setting the minSdkVersion to 21 from 19 solved the issue for me.

defaultConfig { applicationId "com.example" minSdkVersion 21 targetSdkVersion 29 versionCode 23 versionName "1.0" vectorDrawables.useSupportLibrary = true }

Solution no. 10:

This also happened to me but using Dynamic Features. I already had Java 8 compatibility enabled in the app module but I had to add this compatibility lines to the Dynamic Feature module and then it worked.