先看效果图

组件XKeyboard.vue

<template>
  <div id="XKeyBoard" style="display:none;" :style="{width: width+'vw',height: height+'vw',left:left+'px',top:top+'px'}" ref="XKeyBoard">
    <div class="x-top">
      <div @click.stop="clean"><img src="@/assets/imgs/keyborad.png" />清空</div>
      <div></div>
      <div><img src="@/assets/imgs/drop_down.png" @click="close()" /></div>
    </div>
    <div class="x-num" v-for="(ke,index) in keys" :key="index">
      <div @click.stop="entry(lk)" v-for="lk in ke" :key="'k'+lk">{{lk}}</div>
    </div>
  </div>
</template>

<script>
export default {
  name: 'XKeyBoard',
  data() {
    return {
      left: 0,
      top: 0,
      target: null,
      keys: [
        ['1', '2', '3'],
        ['4', '5', '6'],
        ['7', '8', '9'],
        ['.', '0', 'x']
      ]
    };
  },
  props: ['width', 'height'],
  methods: {
    // 外部输入框事件传值过来
    focuss(left, top, input_height, height, width, target) {
      // 展示键盘
      document.getElementById('XKeyBoard').style.display = 'block';
      this.target = target;
      //   获取键盘的高度
      let key_height = document.getElementById('XKeyBoard').clientHeight;
      let key_width = document.getElementById('XKeyBoard').clientWidth;
      //   判定键盘需要处于input上面还是下面
      if (top < height / 2) { // input位置小于屏幕50%高度
        this.top = top + input_height * 2; // 键盘位置=input顶部坐标值+input高度*2
      } else { // 其他
        this.top = top - input_height - key_height; // 键盘顶部坐标值=input框顶部坐标值-input高度-键盘高度
      }
      // 右侧超出窗口，自动调整
      if (width - left < key_width) {
        this.left = width - input_height - key_width; // 键盘左边坐标值=屏幕宽-input高度-键盘宽度
      } else {
        this.left = left + input_height; // 键盘左边坐标值=input左边坐标值-input高度
      }
    },
    // 点击键盘事件
    entry(value) {
      // 匹配0-9和.对input对象内容累加
      if (/^([0-9]{1})$/g.test(value) || value == '.') {
        this.target.value += value;
      } else { // 删除键清空input对象内容
        this.target.value = this.target.value.slice(0, this.target.value.length - 1);
      }
    },
    // 隐藏键盘自身
    close() {
      document.getElementById('XKeyBoard').style.display = 'none';
    },
    // 清空内容
    clean() {
      this.target.value = '';
    }
  }
}
</script>

<style lang="less" scoped>
// 外框位置对照浏览器窗口大小
#XKeyBoard {
  position: fixed;
  border: 0.1vw solid #dcdee2;
  user-select: none;
  color: #515a6e;
  border-radius: 2px;
  background: white;
  z-index: 100;
  // 顶部居中
  .x-top {
    width: 100%;
    height: 11%;
    display: flex;
    justify-content: center;
    // 所有div横向居中
    div {
      display: flex;
      align-items: center;
      img {
        width: 2vw;
        height: 2vw;
      }
    }
    // 标题区向左对齐
    div:nth-child(1) {
      justify-content: flex-start;
      width: 6vw;
    }
    // 空白区占据宽度
    div:nth-child(2) {
      width: 12vw;
    }
    // 关闭按钮区右对齐
    div:nth-child(3) {
      width: 2vw;
      justify-content: flex-end;
      cursor: pointer;
    }
    // 所有按钮触发效果
    div:active {
      opacity: 0.6;
      background: rgb(90, 89, 89);
    }
  }
  //  数字区宽高、盒子、框线
  .x-num {
    width: 100%;
    height: 22.1%;
    display: flex;
    border-top: 1px solid #dcdee2;
    // 所有按钮居中，改变鼠标样式
    div {
      width: 33.33%;
      display: flex;
      justify-content: center;
      align-items: center;
      cursor: pointer;
    }
    // 按钮触发效果
    div:active {
      background: rgb(90, 89, 89);
      color: white;
    }
  }
  .x-num > div:nth-child(3n + 1),
  .x-num > div:nth-child(3n + 2) {
    border-right: 1px solid #dcdee2;
  }
}
</style>

引用

main.js

import Vue from 'vue'
import App from './App.vue'
import XKeyboard from '@/components/XKeyboard';

Vue.config.productionTip = false
Vue.component('x-keyboard',XKeyboard);

new Vue({
  render: h => h(App),
}).$mount('#app')

App.vue

<template>
  <div id="app">
    <x-keyboard :width="21" :height="16" ref="keyboard" :left="left" :top="top"></x-keyboard>
    <input @focus.stop="focuss($event)"/>
    <input @focus.stop="focuss($event)"/>
    <input style="position:fixed;left:0;top:50vh;" @focus.stop="focuss($event)"/>
    <input style="position:fixed;right:0;top:80vh;" @focus.stop="focuss($event)"/>
  </div>
</template>

<script>

export default {
  name: 'App',
  data() {
    return {
      left: 0,
      top: 0,
      input_height: 0,
      height: innerHeight,
      width: innerWidth,
    };
  },

  methods: {
    // 获取焦点事件
    focuss(event) {
      let input_height = event.target.offsetHeight;
      let left = event.target.offsetLeft;
      let top = event.target.offsetTop;
      // 调用键盘组件的方法，传过去input的left、top、height
      // 以及(浏览器窗口高宽)、event.target(当前点击的input)
      this.$refs.keyboard.focuss(left, top, input_height, this.height, this.width, event.target);
    },
  },

}
</script>

<style>
#app {
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
}
</style>