Add Facebook Login

app/src/main/java/dragosholban/com/bestphotos/MainActivity.java

@@ -1,13 +1,55 @@
package dragosholban.com.bestphotos;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

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 MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getName();
    private CallbackManager callbackManager;

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

        LoginButton loginButton = findViewById(R.id.login_button);
        loginButton.setReadPermissions(Arrays.asList("email"));

        // Callback registration
        callbackManager = CallbackManager.Factory.create();
        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                Log.d(TAG, "Facebook login token: " + loginResult.getAccessToken().getToken());
            }

            @Override
            public void onCancel() {
                Log.d(TAG, "Facebook login canceled.");
            }

            @Override
            public void onError(FacebookException error) {
                Log.d(TAG, "Facebook login error: " + error.getMessage());
            }
        });
    }

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

app/src/main/res/layout/activity_main.xml

@@ -6,10 +6,10 @@
    android:layout_height="match_parent"
    tools:context="dragosholban.com.bestphotos.MainActivity">

    <TextView
    <com.facebook.login.widget.LoginButton
        android:id="@+id/login_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"