Login Facebook en Android, código usado en el video: https://www.youtube.com/watch?v=1HgM_vc-rSc

activity_login.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="tech.alvarez.today.LoginActivity">

    <com.facebook.login.widget.LoginButton
        android:id="@+id/loginButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:paddingBottom="10dp"
        android:paddingTop="10dp" />

</RelativeLayout>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="tech.alvarez.today.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/welcome"
        android:textSize="20sp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:onClick="logout"
        android:text="@string/logout" />

</RelativeLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="tech.alvarez.today">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:name=".TodayApp"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <meta-data
            android:name="com.facebook.sdk.ApplicationId"
            android:value="@string/facebook_app_id" />

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".LoginActivity"></activity>
    </application>

</manifest>

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.0"

    defaultConfig {
        applicationId "tech.alvarez.today"
        minSdkVersion 15
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:24.0.0'

    compile 'com.facebook.android:facebook-android-sdk:[4,5)'
}

LoginActivity.java

package tech.alvarez.today;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;

import com.facebook.CallbackManager;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;

import java.util.Arrays;

public class LoginActivity extends AppCompatActivity {

    private LoginButton loginButton;
    private CallbackManager callbackManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        callbackManager = CallbackManager.Factory.create();

        loginButton = (LoginButton) findViewById(R.id.loginButton);

        loginButton.setReadPermissions(Arrays.asList("email"));

        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                goMainScreen();
            }

            @Override
            public void onCancel() {
                Toast.makeText(getApplicationContext(), R.string.cancel_login, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onError(FacebookException error) {
                Toast.makeText(getApplicationContext(), R.string.error_login, Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void goMainScreen() {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(intent);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }
}

MainActivity.java

package tech.alvarez.today;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import com.facebook.AccessToken;
import com.facebook.login.LoginManager;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (AccessToken.getCurrentAccessToken() == null) {
            goLoginScreen();
        }

    }

    private void goLoginScreen() {
        Intent intent = new Intent(this, LoginActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(intent);
    }

    public void logout(View view) {
        LoginManager.getInstance().logOut();
        goLoginScreen();
    }
}

strings.xml

<resources>
    <string name="app_name">Today</string>

    <string name="facebook_app_id">aqui su id app</string>
    <string name="welcome">Bienvenido</string>
    <string name="cancel_login">Se canceló la operación</string>
    <string name="error_login">Ocurrió un error al ingresar</string>
    <string name="logout">Cerrar sesión</string>
</resources>

TodayApp.java

package tech.alvarez.today;

import android.app.Application;

import com.facebook.FacebookSdk;
import com.facebook.appevents.AppEventsLogger;

/**
 * Created by Daniel Alvarez on 21/6/16.
 * Copyright © 2016 Alvarez.tech. All rights reserved.
 */
public class TodayApp extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        FacebookSdk.sdkInitialize(getApplicationContext());
        AppEventsLogger.activateApp(this);
    }
}

excelente! Muchas gracias! vi tu video en tu canal y me ayudo mucho! El de login y el de configurar el SDK