Cannot import Request and Session classes from Facebook Android Sdk - facebook

Question

I am trying to import com.facebook.Request and com.facebook.Session classes with the goal of getting the Facebook friendlist from Facebook into my app.
import com.facebook.Request;
import com.facebook.Session;
But the words Request and Session keep being in red, as Android studio cannot recognize it. Anyone knows how to fix this? I appreciate any insight!
This is my manifest file:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.example.demouser.bond">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".SplashActivity"
android:theme="#style/SplashTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".MainContactScreen"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".IndividualContactActivity"
android:windowSoftInputMode="adjustPan" />
<activity
android:name=".CalendarMainActivity"
android:parentActivityName=".MainContactScreen"
android:windowSoftInputMode="adjustPan" />
<activity
android:name=".IndividualContactPage"
android:parentActivityName=".MainContactScreen"
android:windowSoftInputMode="adjustPan" />
<activity android:name=".TemplateMainActivity" />
<receiver
android:name=".AlarmBroadcastReceiver"
android:enabled="true">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
<meta-data
android:name="com.facebook.accountkit.ApplicationName"
android:value="#string/app_name" />
<meta-data
android:name="com.facebook.sdk.ApplicationId"
android:value="#string/FACEBOOK_APP_ID" />
<meta-data
android:name="com.facebook.accountkit.ClientToken"
android:value="#string/ACCOUNT_KIT_CLIENT_TOKEN" />
<meta-data
android:name="com.facebook.accountkit.FacebookAppEventsEnabled"
android:value="true" />
<activity
android:name="com.facebook.accountkit.ui.AccountKitActivity"
android:theme="#style/Theme.AccountKit"
tools:replace="android:theme" />
<activity android:name=".FacebookLoginActivity" />
</application>
</manifest>
App Gradle file:
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
defaultConfig {
applicationId "com.example.demouser.bond"
minSdkVersion 21
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 {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
implementation 'com.android.support:design:26.1.0'
implementation 'com.android.support:support-v4:26.1.0'
implementation 'com.android.support:recyclerview-v7:26.1.0'
implementation 'com.facebook.android:account-kit-sdk:4.+'
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'
// Facebook Android SDK (everything)
compile 'com.facebook.android:facebook-android-sdk:4.28.0'
}
Project Gradle file:
// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
repositories {
google()
jcenter()
mavenCentral()
}
dependencies {
classpath 'com.android.tools.build:gradle:3.0.1'
// 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
}
And if it is helpful, this is my res/values/string.xml file:
<resources>
<string name="app_name">Bond</string>
<string name="calendar_name">Android Custom Calendar</string>
<string name="current_date">January, 2018</string>
<string name="add_event">ADD CALENDAR EVENT</string>
<string name="sun">SUN</string>
<string name="mon">MON</string>
<string name="tue">TUE</string>
<string name="wed">WED</string>
<string name="thu">THU</string>
<string name="fri">FRI</string>
<string name="sat">SAT</string>
<string name="last_date">30</string>
<string name="action_settings">Settings</string>
<string name="title_item_list">Items</string>
<string name="title_item_detail">Item Detail</string>
<string name="facebook_app_id">137757443587015</string>
<string name="fb_login_protocol_scheme">fb137757443587015</string>
<string name="FACEBOOK_APP_ID">137757443587015</string>
<string name="ACCOUNT_KIT_CLIENT_TOKEN">[ACCOUNT_KIT_CLIENT_TOKEN]</string>
</resources>