title: How to clear a SAPUI5 input field with only value help input allowed?
body: <p>my SAPUI5 app has an <a href="https://sapui5.hana.ondemand.com/#docs/api/symbols/sap.m.Input.html#constructor" rel="nofollow">input</a> field where the valid values must be obtained through a value help:</p>
  
  <pre><code>&lt;Input showValueHelp="true" valueHelpOnly="true"
                             valueHelpRequest="onValueHelpRequest"
                             value="{myModel&gt;/myField}"
  </code></pre>
  
  <p>The value help is realized with a <a href="https://sapui5.hana.ondemand.com/#docs/api/symbols/sap.m.SelectDialog.html" rel="nofollow">SelectDialog</a>, where the only options are </p>
  
  <ol>
  <li>choose one or</li>
  <li>cancel</li>
  </ol>
  
  <p>The problem is now the following flow:</p>
  
  <ol>
  <li>User opens value help dialog to choose one item and presses <em>Confirm</em></li>
  <li>Input field now displays chosen value</li>
  <li>User wants to clear the input, because it's optional</li>
  </ol>
  
  <p>Unfortunately,</p>
  
  <ol>
  <li><code>sap.m.Input</code> doesn't provide a clear button</li>
  <li><code>sap.m.SelectDialog</code> doesn't provide the possibility to add a custom button like <em>Clear</em></li>
  <li>The input is layed out in a SimpleForm with 2 columns, labels and input fields, so it would be hard to add a clear button</li>
  <li>The Gateway entity set which feeds the value help dialog list doesn't have a totally empty line</li>
  <li>I don't like the workaround to switch the SelectDialog to <a href="https://sapui5.hana.ondemand.com/#docs/api/symbols/sap.m.SelectDialog.html#getMultiSelect" rel="nofollow">multiSelect</a> just for the purpose that the user can choose "one or none". I also think it would be hard to explain to the user "if you want to remove the value, hold the control key and click on the previously selected item again".</li>
  </ol>
  
  <p>Any ideas out there how to easily implement a clear button or something similar?</p>