Joomla JForm showon

Question

I would like to extend the functionality of my form I'm using in my admin-backend.

To to that I would like to use the showon-attribute, which should only show a field, if the value of this field is -1:

<field  name="itemid" 
        type="sql"  
        label="COM_BESTIA_FIELD_ITEMS" 
        query="SELECT id, title FROM #__bestia_items WHERE state = 1" 
        key_field="id" 
        value_field="title" 
        required="true">
            <option value="-1">Other</option>
</field>

How can I do this: showon itemid:-1 does not work.

Answer 1

You can show/hide your field with showon when the value of related field matches your defined values for showon. So there should be two fields minimum:

1. Field with values to match.
2. Field to show/hide.

For example:

<field  name="itemid" 
        type="sql"  
        label="COM_BESTIA_FIELD_ITEMS" 
        query="SELECT id, title FROM #__bestia_items WHERE state = 1" 
        key_field="id" 
        value_field="title" 
        required="true">
            <option value="-1">Other</option>
</field>

<field  name="custom" 
        type="sql"  
        label="COM_BESTIA_FIELD_ITEMS" 
        query="SELECT id, title FROM #__bestia_items WHERE state = 1" 
        key_field="id" 
        value_field="title" 
        required="true"
        showon="itemid:-1">
            <option value="-1">Other</option>
</field>

So here your custom field will be displayed when value of itemid field is -1.