TwinColSelect

The TwinColSelect field provides a multiple selection component that shows two lists side by side, with the left column containing unselected items and the right column the selected items. The user can select items from the list on the left and click on the “>>” button to move them to the list on the right. Items can be deselected by selecting them in the right list and clicking on the “<<” button.

Twin Column Selection

TwinColSelect is always in multi-select mode, so its property value is always a collection of the item IDs of the selected items, that is, the items in the right column.

The selection columns can have their own captions, separate from the overall component caption, which is managed by the containing layout. You can set the column captions with setLeftColumnCaption() and setRightColumnCaption().

Java

TwinColSelect select = new TwinColSelect("Select Targets");
// Put some items in the select
select.addItems("Mercury", "Venus", "Earth", "Mars",
        "Jupiter", "Saturn", "Uranus", "Neptune");
// Few items, so we can set rows to match item count
select.setRows(select.size());
// Preselect a few items by creating a set
select.setValue(new HashSet<String>(
    Arrays.asList("Venus", "Earth", "Mars")));
// Handle value changes
select.addValueChangeListener(event -> // Java 8
    layout.addComponent(new Label("Selected: " +
            event.getProperty().getValue())));

See the on-line example.

The resulting component is shown in Twin Column Selection.

The setRows() method sets the height of the component by the number of visible items in the selection boxes. Setting the height with setHeight() to a defined value overrides the rows setting.

Common selection component features are described in “Selection Components”.

CSS Style Rules

CSS

.v-select-twincol {}
  .v-select-twincol-options-caption {}
  .v-select-twincol-selections-caption {}
  .v-select-twincol-options {}
  .v-select-twincol-buttons {}
    .v-button {}
      .v-button-wrap {}
        .v-button-caption {}
    .v-select-twincol-deco {}
  .v-select-twincol-selections {}

The TwinColSelect component has an overall v-select-twincol style. If set, the left and right column captions have v-select-twincol-options-caption and v-select-twincol-options-caption style names, respectively. The left box, which displays the unselected items, has v-select-twincol-options-caption style and the right box, which displays the selected items, has v-select-twincol-options-selections style. Between them is the button area, which has overall v-select-twincol-buttons style; the actual buttons reuse the styles for the Button component. Between the buttons is a divider element with v-select-twincol-deco style.