Facebook login NullPointerException

You need to change or add this in your manifest file

 <activity
        android:name="com.example.LoginActivity"
        android:label="@string/app_name" 
        android:parentActivityName="com.example.MainActivity" >


 </activity>
 <activity android:name="com.facebook.LoginActivity"
              android:theme="@android:style/Theme.Translucent.NoTitleBar"
              android:label="@string/app_name" />
    <meta-data android:name="com.facebook.sdk.ApplicationId"   android:value="@string/app_id"/>

I cannot take credit for this, all credit must go to the guy who posted the answer here I am purely adding the code for ease for you and because I got told to by someone who previously deleted the answer.