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"