message: [Improvement] Area: add change event
diff: <template>
  <picker
  - :class="b()"
  ref="picker"
  + :class="b()"
  show-toolbar
  value-key="name"
  :title="title"
  @@ -156,6 +156,7 @@ export default create({
  } else if (index === 1) {
  picker.setColumnValues(2, this.getList('county', code.slice(0, 4)));
  }
  + this.$emit('change', picker, values, index);
  },
  getValues() {
  