title: Butter Knife return null pointer
body: <p>I want to using Butter Knife in my project.I did everything according to the Butter Knife tutorial.
  But when I set anything to the views (setText, setClickListener ...) I got null object reference exception.</p>
  
  <p>This is my code:</p>
  
  <pre><code>public class LoginActivity extends AppCompatActivity implements LoginView, View.OnClickListener {
  
  @BindView(R.id.acEtUsername) AppCompatEditText userName;
  @BindView(R.id.acEtPassword) AppCompatEditText password;
  @BindView(R.id.prgCheckLogin) ProgressBar prgCheckLogin;
  @BindView(R.id.btnLogin) Button btnLogin;
  
  LoginPresenter loginPresenter;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_login);
  
      ButterKnife.bind(this);
      ButterKnife.setDebug(true);
  
      loginPresenter = new LoginPresenterImpl(this);
  
      btnLogin.setOnClickListener(this); // or userName.setText("userName");
    }
    /** Other Methods **/
  </code></pre>
  
  <p>activity_login.xml</p>
  
  
  
  <pre class="lang-html prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      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"&gt;
  
      &lt;android.support.v7.widget.AppCompatEditText
          android:id="@+id/acEtUsername"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_gravity="center"
          android:gravity="center"
          android:layout_marginRight="32dp"
          android:layout_marginLeft="32dp"
          android:hint="@string/user_name"/&gt;
  
      &lt;android.support.v7.widget.AppCompatEditText
          android:id="@+id/acEtPassword"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_gravity="center"
          android:gravity="center"
          android:layout_marginTop="8dp"
          android:layout_marginRight="32dp"
          android:layout_marginLeft="32dp"
          android:hint="@string/password"/&gt;
  
      &lt;Button
          android:id="@+id/btnLogin"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center"
          android:layout_margin="8dp"
          android:text="@string/login"/&gt;
  
      &lt;ProgressBar
          android:id="@+id/prgCheckLogin"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:visibility="gone"
          android:layout_gravity="center|bottom"/&gt;
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  
  
  <p>And error log</p>
  
  <pre><code> Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.AppCompatEditText.setText(java.lang.CharSequence)' on a null object reference
  </code></pre>
  
  <p>What's wrong in my code ?</p>
  
  <p>Thanks</p>