title: How to restrict the EditText to accept only alphanumeric characters
body: <p>How can I restrict an <code>EditText</code> to accept only alphanumeric characters, with both lowercase and uppercase characters showing as uppercase in the <code>EditText</code>?</p>
  
  <pre><code>&lt;EditText
      android:id="@+id/userInput"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:inputType="textMultiLine"
      android:minLines="3" &gt;
  
      &lt;requestFocus /&gt;
  &lt;/EditText&gt;
  </code></pre>
  
  <p>If a user types in lowercase "abcd", the <code>EditText</code> should automatically show uppercase "ABCD" without needing to restrict the keyboard to uppercase.</p>