html5 Canvas 如何自适应屏幕大小（vue）

创建canvas

       <div  class="twovideo">
           <canvas id="playground" width="560;" height="306"></canvas>
       </div>

.twovideo {
    
    
  width: 100%;
  height: 306px;
  canvas {
    
    
    width: 100%;
    height: 100%;
    display: block;
  }
}

创建出的画布不能随着浏览器窗口大小的改变而动态的改变画布的大小。 但是作为一个百分比的弹窗，在不同屏幕下表现不同，所以需要做自适应

在vue中，新建一个resize.js文件

import {
    
     debounce } from '@/utils'

export default {
    
    
  data() {
    
    
    return {
    
    
      $_sidebarElm: null,
      $_resizeHandler: null
    }
  },
  mounted() {
    
    
    this.initListener()
  },
  activated() {
    
    
    if (!this.$_resizeHandler) {
    
    
      // avoid duplication init
      this.initListener()
    }

    // when keep-alive chart activated, auto resize
    this.resize()
  },
  beforeDestroy() {
    
    
    this.destroyListener()
  },
  deactivated() {
    
    
    this.destroyListener()
  },
  methods: {
    
    
    // use $_ for mixins properties
    // https://vuejs.org/v2/style-guide/index.html#Private-property-names-essential
    $_sidebarResizeHandler(e) {
    
    
      if (e.propertyName === 'width') {
    
    
        this.$_resizeHandler()
      }
    },
    initListener() {
    
    
      this.$_resizeHandler = debounce(() => {
    
    
        this.resize()
      }, 100)
      window.addEventListener('resize', this.$_resizeHandler)

      this.$_sidebarElm = document.getElementsByClassName('sidebar-container')[0]
      this.$_sidebarElm && this.$_sidebarElm.addEventListener('transitionend', this.$_sidebarResizeHandler)
    },
    destroyListener() {
    
    
      window.removeEventListener('resize', this.$_resizeHandler)
      this.$_resizeHandler = null
      this.$_sidebarElm && this.$_sidebarElm.removeEventListener('transitionend', this.$_sidebarResizeHandler)
    },
    resize() {
    
    
      const {
    
     chart } = this
      chart && chart.resize()
    }
  }
}

其中引入的debounce 防抖函数如下 utils/index.js

/**
 * @param {Function} func
 * @param {number} wait
 * @param {boolean} immediate
 * @return {*}
 */
export function debounce(func, wait, immediate) {
    
    
  let timeout, args, context, timestamp, result

  const later = function () {
    
    
    // 据上一次触发时间间隔
    const last = +new Date() - timestamp

    // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
    if (last < wait && last > 0) {
    
    
      timeout = setTimeout(later, wait - last)
    } else {
    
    
      timeout = null
      // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
      if (!immediate) {
    
    
        result = func.apply(context, args)
        if (!timeout) context = args = null
      }
    }
  }

  return function (...args) {
    
    
    context = this
    timestamp = +new Date()
    const callNow = immediate && !timeout
    // 如果延时不存在，重新设定延时
    if (!timeout) timeout = setTimeout(later, wait)
    if (callNow) {
    
    
      result = func.apply(context, args)
      context = args = null
    }

    return result
  }
}

最后在页面mixins注入resize.js

import resize from '../../utils/mixins/resize'

mixins: [resize],//和data同级

就可以实现canvas自适应了。