Ribbon Custom Action Elements.xml

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <CustomAction Id="9b3d1a59-78ca-45da-aa2c-4964e3f68c58.AppHost-RCA"
                RegistrationType="List"
                RegistrationId="100"
                Location="CommandUI.Ribbon"
                Sequence="10001"
                Title="Invoke &apos;AppHost_RCA&apos; action">
    <CommandUIExtension>
      <!-- 
      Update the UI definitions below with the controls and the command actions
      that you want to enable for the custom action.
      -->
      <CommandUIDefinitions>
        <CommandUIDefinition Location="Ribbon.ListItem.Actions.Controls._children">
          <Button Id="Ribbon.ListItem.Actions.AppHost-RCAButton"
                  Alt="Request App"
                  Sequence="100"
                  Command="Invoke_AppHost-RCAButtonRequest"
                  LabelText="Request App"
                  TemplateAlias="o1"
                  Image32by32="_layouts/15/images/placeholder32x32.png"
                  Image16by16="_layouts/15/images/placeholder16x16.png" />
        </CommandUIDefinition>
      </CommandUIDefinitions>
      <CommandUIHandlers>
        <CommandUIHandler Command="Invoke_AppHost-RCAButtonRequest"
                          CommandAction="~appWebUrl/Pages/Default.aspx"/>
      </CommandUIHandlers>
    </CommandUIExtension >
  </CustomAction>
</Elements>