点击出现输入框

<!--index.wxml-->
<view class="container" class="zn-uploadimg">
    <button type="primary"bindtap="modalinput">测试</button> 
</view>
<modal hidden="{{hiddenmodalput}}" title="评论" confirm-text="确定" cancel-text="取消" bindcancel="cancel" bindconfirm="confirm">
    <input type='text'placeholder="请输入内容" auto-focus/>
</modal>

//index.js
//获取应用实例
var app = getApp()
Page({
  data: {
    hiddenmodalput: true,
    //可以通过hidden是否掩藏弹出框的属性，来指定那个弹出框
  },
  //点击按钮痰喘指定的hiddenmodalput弹出框
  modalinput: function () {
    this.setData({
      hiddenmodalput: !this.data.hiddenmodalput
    })
  },
  //取消按钮
  cancel: function () {
    this.setData({
      hiddenmodalput: true
    });
  },
  //确认
  confirm: function () {
    this.setData({
      hiddenmodalput: true
    })
  }

})