<RelativeLayout        xmlns:android="http://schemas.android.com/apk/res/android"

  xmlns:tools="http://schemas.android.com/tools"

  android:layout_width="match_parent"

  android:layout_height="match_parent" >

   <TextView

     android:id="@+id/tv_test"

     android:layout_width="wrap_content"

     android:layout_height="wrap_content"

     android:layout_centerHorizontal="true"

     android:layout_centerVertical="true"

     android:text="@string/hello_world"

     tools:context=".MainActivity" />

</RelativeLayout>

 package com.msquirrel.main;

 import butterknife.ButterKnife;

 import butterknife.InjectView;

 import butterknife.OnClick;

 import android.os.Bundle;

 import android.app.Activity;

 import android.widget.TextView;

 public class MainActivity extends Activity {

   @InjectView(R.id.tv_test)

   TextView tvTest;

   @Override

   public void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      setContentView(R.layout.activity_main);

      ButterKnife.inject(this);

      tvTest.setText("test");

   }

   @OnClick(R.id.tv_test)

   public void sayHi() {

      tvTest.setText("Hello!");

   }

 }