Android plugin

Android Gradle plugin adds several features that are specific to building Android apps. To add plugin you must add repository and dependency in top-level buld.gradle file

java plugin incompatible with android plugin. You should remove java, also replace kotlin to the kotlin-android.

buildscript {
    repositories {
        // Gradle 4.1 and higher include support for Google's Maven repo using
        // the google() method. And you need to include this repo to download
        // Android Gradle plugin 3.0.0 or higher.
        google()
        ...
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.1.0'
    }
}

The on module level add plugin

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
// depricated
// apply plugin: 'kotlin-android-extensions'

After that, you can use the android block

android {
    compileSdkVersion 30

    buildFeatures {
        viewBinding true
    }

    defaultConfig {
        applicationId "com.darkraha.mobibrowser"
        minSdkVersion 21
        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'
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    
     // For Kotlin projects
    kotlinOptions {
        languageVersion = "1.4"
        jvmTarget = '1.8'
        // noStdlib = true // don't link with stdlib.
    }
}

Java 8

Java 8 has been supported natively since Android SDK 26.

Android Gradle plugin 4+ allows to use a number of Java 8 language APIs without requiring a minimum API level for your app ( full list):

• java.util.stream
• subset of java.time
• java.util.function
• recent additions to java.util.{Map,Collection,Comparator}
• optionals (java.util.Optional, java.util.OptionalInt and java.util.OptionalDouble)
• some additions to java.util.concurrent.atomic
• ConcurrentHashMap (with bug fixes for Android 5.0)

android {
  defaultConfig {
    // Required when setting minSdkVersion to 20 or lower
    multiDexEnabled true
  }

  compileOptions {
    // Flag to enable support for the new language APIs
    coreLibraryDesugaringEnabled true
    // Sets Java compatibility to Java 8
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

dependencies {
  coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'
}