Failed to load AppCompat ActionBar with unknown error android studio 3.0

Question

After updating android studio to version 3.0, I can\'t preview layout of my app, I get the error like:

\'Failed to load AppCompat ActionBar with unknown erro         


        

Answer 1

First, you need to use the same version of compileSdkVersion, buildToolsVersion, targetSdkVersion, and support library version. I see that you want to use buildToolsVersion '26.0.2'. So, change all of them to version 26.

Second, you need to clean up your build.gradle. There is no need for duplicate dependencies.

Third, try clean and build your project. As the last resort, try File -> Invalidate Caches/Restart...

Your app build.gradle should be something like this:

apply plugin: 'com.android.application'

android {
  compileSdkVersion 26
  buildToolsVersion '26.0.2'
  defaultConfig {
    applicationId 'com.halloo'
    minSdkVersion 16
    targetSdkVersion 26
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
    release {
      minifyEnabled false
      proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
  }
  productFlavors {
  }
}

dependencies {
  compile fileTree(include: ['*.jar'], dir: 'libs')
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
  })
  compile 'com.android.support:appcompat-v7:26.1.0'
  compile 'com.android.support:design:26.1.0'
  compile 'com.android.support:support-v4:26.1.0'
  compile 'com.squareup.okhttp3:okhttp:3.5.0'
  compile 'com.android.support:recyclerview-v7:26.1.0'
  compile 'com.mikhaellopez:hfrecyclerview:1.0.0'
  testCompile 'junit:junit:4.12'
}

You also need to check for your project build.gradle. It should contain build:gradle:3.0.0 (as @dheeraj-joshi has pointing out), something like this:

buildscript {
  repositories {
    jcenter()
    mavenCentral()
  }
  dependencies {
    classpath 'com.android.tools.build:gradle:3.0.0'
  }
}

allprojects {
  repositories {
    jcenter()
    mavenCentral()
//    maven { url "https://maven.google.com" }
    google()
  }
}


task clean(type: Delete) {
  delete rootProject.buildDir
}

Then, you need to check your gradle version. It should at least using gradle-4.1.