title: cannot be resolved or is not a field Android
body: <p>I have checked similar question on StackOverflow but I couldn't find a solution that solves my problem. My strings.xml : </p>
  
  <pre><code>&lt;string name="true_button"&gt;True&lt;/string&gt;
  &lt;string name="false_button"&gt;False&lt;/string&gt;
  </code></pre>
  
  <p>My Activity Java : </p>
  
  <pre><code>private Button mTrueButton;
  private Button mFalseButton;
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_quiz);
  mTrueButton = (Button)findViewById(R.id.true_button);
  mFalseButton = (Button)findViewById(R.id.false_button);
  }
  </code></pre>
  
  <p>I get <strong>cannot be resolved or is not a field</strong>  for <strong>R.id.true_button</strong> and <strong>R.id.false_button</strong></p>
  
  <p>I can see those variables in R.java file. Can you tell me how to fix these errors? Thanks.</p>