A valid Facebook app id must be set in the AndroidManifest.xml

Add below in build.gradle(Module:app) file:

repositories {
    mavenCentral()
}

and

compile 'com.facebook.android:facebook-android-sdk:4.10.0'

now add below in AndroidManifest.xml file :

 <activity android:name="com.facebook.FacebookActivity"
           android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"
           android:theme="@android:style/Theme.Translucent.NoTitleBar"
           android:label="@string/app_name" />

add following in activity_main.xml file :

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.demonuts.fblogin.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="#000"
    android:layout_marginLeft="10dp"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:id="@+id/text"/>

<com.facebook.login.widget.LoginButton
    android:id="@+id/btnfb"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="10dp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

</LinearLayout>

The meta-data in my case were located out of the application scope. Normally, it should be located in your manifest like this:

<application>
      ...
      <meta-data
                android:name="com.facebook.sdk.ApplicationId"
                android:value="@string/facebook_app_id" />
    </application>