vaadin-grid trouble using "selected"

Flow
1 
 <vaadin-grid-column resizable>
        <template class="header">
            Edit
        </template>
        <template>
          [[selected]
]
          <paper-button hidden$="[[!selected]
]" file="[[item]
]" on-click="_editFileRequest">Edit</paper-button></template>
      </vaadin-grid-column>

When this grid loads selected is displayed correctly as “False”. But if I click on the row it remains unchanged. I have also tried:

 <vaadin-grid-column resizable>
        <template class="header">
            Edit
        </template>
        <template>
          {{selected}}
          <paper-button hidden$="[[_hideEditBtn(selected)]
]" file="[[item]
]" on-click="_editFileRequest">Edit</paper-button></template>
      </vaadin-grid-column>

Any ideas?

2

Solution is to populat the selectedItems array myself:

Eg.

_activeItemChanged(item){
this.$.grid.selectedItems = this.item ? [this.item]
: ;
}