paper-radio-group.html

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@license
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<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
<link rel="import" href="../iron-menu-behavior/iron-menubar-behavior.html">
<link rel="import" href="../paper-radio-button/paper-radio-button.html">

<!--
Material design: [Radio button](https://www.google.com/design/spec/components/selection-controls.html#selection-controls-radio-button)

`paper-radio-group` allows user to select at most one radio button from a set.
Checking one radio button that belongs to a radio group unchecks any
previously checked radio button within the same group. Use
`selected` to get or set the selected radio button.

The <paper-radio-buttons> inside the group must have the `name` attribute
set.

Example:

    <paper-radio-group selected="small">
      <paper-radio-button name="small">Small</paper-radio-button>
      <paper-radio-button name="medium">Medium</paper-radio-button>
      <paper-radio-button name="large">Large</paper-radio-button>
    </paper-radio-group>

Radio-button-groups can be made optional, and allow zero buttons to be selected:

    <paper-radio-group selected="small" allow-empty-selection>
      <paper-radio-button name="small">Small</paper-radio-button>
      <paper-radio-button name="medium">Medium</paper-radio-button>
      <paper-radio-button name="large">Large</paper-radio-button>
    </paper-radio-group>

See <a href="paper-radio-button">paper-radio-button</a> for more
information about `paper-radio-button`.


Custom property | Description | Default
----------------|-------------|----------
`--paper-radio-group-item-padding` | The padding of the item | `12px`

@group Paper Elements
@element paper-radio-group
@hero hero.svg
@demo demo/index.html
-->

<dom-module id="paper-radio-group">
  <template>
    <style>
      :host {
        display: inline-block;
      }

      :host ::content > * {
        padding: var(--paper-radio-group-item-padding, 12px);
      }
    </style>

    <content id="items" select="*"></content>
  </template>
</dom-module>

<script>
  Polymer({
    is: 'paper-radio-group',

    behaviors: [
      Polymer.IronMenubarBehavior
    ],

    hostAttributes: {
      role: 'radiogroup',
      tabindex: 0
    },

    properties: {
      /**
       * Fired when the radio group selection changes.
       *
       * @event paper-radio-group-changed
       */

      /**
       * Overriden from Polymer.IronSelectableBehavior
       */
      attrForSelected: {
        type: String,
        value: 'name'
      },

      /**
       * Overriden from Polymer.IronSelectableBehavior
       */
      selectedAttribute: {
        type: String,
        value: 'checked'
      },

      /**
       * Overriden from Polymer.IronSelectableBehavior
       */
      selectable: {
        type: String,
        value: 'paper-radio-button'
      },

      /**
       * If true, radio-buttons can be deselected
       */
      allowEmptySelection: {
        type: Boolean,
        value: false
      }
    },

    /**
     * Selects the given value.
     */
     select: function(value) {
      var newItem = this._valueToItem(value);
      if (newItem && newItem.hasAttribute('disabled')) {
        return;
      }

      if (this.selected) {
        var oldItem = this._valueToItem(this.selected);

        if (this.selected == value) {
          // If deselecting is allowed we'll have to apply an empty selection.
          // Otherwise, we should force the selection to stay and make this
          // action a no-op.
          if (this.allowEmptySelection) {
            value = '';
          } else {
            if (oldItem)
              oldItem.checked = true;
            return;
          }
        }

        if (oldItem)
          oldItem.checked = false;
      }

      Polymer.IronSelectableBehavior.select.apply(this, [value]);
      this.fire('paper-radio-group-changed');
    },

    _activateFocusedItem: function() {
      this._itemActivate(this._valueForItem(this.focusedItem), this.focusedItem);
    },

    _onUpKey: function(event) {
      this._focusPrevious();
      event.preventDefault();
      this._activateFocusedItem();
    },

    _onDownKey: function(event) {
      this._focusNext();
      event.preventDefault();
      this._activateFocusedItem();
    },

    _onLeftKey: function(event) {
      Polymer.IronMenubarBehaviorImpl._onLeftKey.apply(this, arguments);
      this._activateFocusedItem();
    },

    _onRightKey: function(event) {
      Polymer.IronMenubarBehaviorImpl._onRightKey.apply(this, arguments);
      this._activateFocusedItem();
    }
  });
</script>