Error inflating class com.facebook.widget.LoginButton with Facebook SDK 4.0.1

Caused by: The SDK has not been initialized, make sure to call FacebookSdk.sdkInitialize() first.

Make sure you initialized facebook SDK before setContentView.

FacebookSdk.sdkInitialize(getApplicationContext());
setContentView(R.layout.activity_main);

Don't forget to added the android app id in the android manifest inside the application xml tag

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

Only add this methods of your app's Application class::

FacebookSdk.sdkInitialize(getApplicationContext());

AppEventsLogger.activateApp(this);

Befeore: setContentView in onCreate Activity.

In dependencies import:

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

Enjoy :)

In facebook sdk 4.0.1, LoginButton class is not inside com.facebook.widget package. It is inside com.facebook.login.widget package. So your xml declaration should look like this:

  <com.facebook.login.widget.LoginButton
    android:id="@+id/connectWithFbButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:layout_gravity="center_horizontal"
    android:text="  connect_with_facebook" />