怎么实现点击按钮，让光标聚焦到指定的输入框？

<input focus="{{focusId == 1}}" />
<input focus="{{focusId == 2}}" />
<input focus="{{focusId == 3}}" />
<button bindtap="onClick">按钮</button>

onClick() {
  if (...) {
    this.setData({
      focusId: 1
    })
  } else if ...
}