fix the error : Plugin with id ‘com.android.application’ not found

When I create a new project in android studio, at first every thing is o.k and it runs on my mobile phone. But if I press the sync button then a terrible error(which I afraid of and hate it) is appeared: “Plugin with id ‘com.android.application’ not found”. I search and read all answers related to this error and do every thing. But my problem is also remained. Here is my build.gradle(module.app):

apply plugin: 'com.android.application'

android {
     compileSdkVersion 27
     defaultConfig {
         applicationId "com.example.masood.pietest"
         minSdkVersion 16
         targetSdkVersion 27
         versionCode 1
         versionName "1.0"
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
     }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
 }

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.0'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}

and here is my build.gradle(project):

buildscript {

    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.0-alpha09'


        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
   }
}

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

Really, I don’t know what I need to do… Could anyone help me?