效果图

源代码
.josn
弹出框用了vant小程序的ui，需要下载。也可以不用，抽取关键代码即可。
vant-weapp：https://vant-contrib.gitee.io/vant-weapp/#/quickstart

  "usingComponents": {
    "van-popup": "@vant/weapp/popup/index"
  },

wxml

<van-cell title="展示弹出层" is-link bind:click="showPopup" />

<van-popup show="{{ show }}" closeable position="bottom" custom-style="height: 60%" bind:close="onClose">
	<view class="Toptitle">请输入密码</view>
	
	<!-- 以下为输入密码关键代码 -->
	<form bindsubmit="formSubmit">
		<view class='content'>
			<block wx:for="{{Length}}" wx:key="item">
				<input class='iptbox' value="{{Value.length>=index+1?Value[index]:''}}" disabled password='{{ispassword}}' catchtap='Tap'></input>
			</block>
		</view>
		<input name="password" password="{{true}}" class='ipt' maxlength="{{Length}}" focus="{{isFocus}}" bindinput="Focus"></input>
		<view>
			<button class="btn-area" type='primary' disabled='{{disabled}}' formType="submit">下一步</button>
		</view>
	</form>
	
</van-popup>

js

// pages/home/home.js
Page({

  /**
   * 页面的初始数据
   */
  data: {
    Length: 6, //输入框个数
    isFocus: false, //聚焦 唤起键盘
    Value: "", //输入的密码内容
    ispassword: false, //是否密文显示 true为密文， false为明文。
    disabled: true,//下一步按钮可否可点击
    show: false,  //弹出框
  },


  Focus(e) {
    var that = this;
    console.log(e.detail.value);
    var inputValue = e.detail.value;
    var ilen = inputValue.length;
    if (ilen == 6) {
      that.setData({
        disabled: false,
      })
    } else {
      that.setData({
        disabled: true,
      })
    }
    that.setData({
      Value: inputValue,
    })
  },
  Tap() {
    var that = this;
    that.setData({
      isFocus: true,
    })
  },
  //提交
  formSubmit(e) {
  	//  拿到密码可进行下一步操作，判断密码是否正确在进行一系列交易
	 console.log(e.detail.value.password)
  },
  
  showPopup() {
    this.setData({ show: true });
  },
  onClose() {
    this.setData({
      show: false
    });
  },

  /**
   * 生命周期函数--监听页面加载
   */
  onl oad: function (options) {

  },
})

css

.Toptitle{
  text-align: center;
  margin: 60rpx auto 46rpx;
  font-size: 40rpx;
  font-weight: 600;
}
.content{
  /* width: 660rpx; */
  padding:0 45rpx;
  display: flex;
  justify-content: space-around;
  align-items: center;
  margin-top: 100rpx;
}
.iptbox{
  width: 110rpx;
  height: 96rpx;
  border:1rpx solid #ddd;
  box-sizing: border-box;
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
}
.ipt{
  width: 0;
  height: 0;
}
.btn-area{
  width: 80%;
  margin-top: 60rpx;
}