title: android error on tutorial cannot find symbol variable activity_display_message
body: <p>I am trying to learn android app building through tutorials and Android Studio. Some of the comments regarding xml and imports were helpfult. I am down to one error. I get this error Error:(22, 57) error: cannot find symbol variable activity_display_message</p>
  
  <p>The errors regarding imports I have fixed with some searching on stack flow. I am missing something</p>
  
  <p>DisplayMessageActivity</p>
  
  <pre><code>package com.example.rpinto.myfirstapp;
  
  import android.content.Intent;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.ViewGroup;
  import android.widget.TextView;
  
  public class DisplayMessageActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_display_message);
  
          Intent intent = getIntent();
          String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
          TextView textView = new TextView(this);
          textView.setTextSize(40);
          textView.setText(message);
  
          ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
          layout.addView(textView);
      }
  }
  </code></pre>
  
  <p>activity_display_message.xml</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;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"
      android:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      tools:context="com.example.rpinto.myfirstapp.DisplayMessageActivity"
      tools:showIn="@layout/activity_display_message"
      android:id="@+id/content"&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>build.gradle</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 23
      buildToolsVersion "24.0.1"
  
      defaultConfig {
          applicationId "com.example.rpinto.myfirstapp"
          minSdkVersion 15
          targetSdkVersion 23
          versionCode 1
          versionName "1.0"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      testCompile 'junit:junit:4.12'
      compile 'com.android.support:appcompat-v7:23.4.0'
  }
  </code></pre>