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How to use Vue+canvas to implement mobile handwriting pad function

php中世界最好的语言
php中世界最好的语言Original
2018-06-01 11:31:132321browse

This time I will show you how to use Vue canvas to implement the mobile handwriting pad function, and what are the precautions for using Vue canvas to implement the mobile handwriting pad function. The following is a practical case, let’s take a look. .

<template>
 <p class="hello">
<!--touchstart,touchmove,touchend,touchcancel 这-->
 <button type="" v-on:click="clear">清除</button>
 <button v-on:click="save">保存</button>
  <canvas id="canvas" width="300" height="600" style="border:1px solid black">Canvas画板</canvas>
  <img v-bind:src="url" alt="">
 </p>
 
</template>
<script>
var draw;
var preHandler = function(e){e.preventDefault();}
class Draw {
  constructor(el) {
    this.el = el
    this.canvas = document.getElementById(this.el)
    this.cxt = this.canvas.getContext('2d')
    this.stage_info = canvas.getBoundingClientRect()
    this.path = {
      beginX: 0,
      beginY: 0,
      endX: 0,
      endY: 0
    }
  }
  init(btn) {
    var that = this; 
    
    this.canvas.addEventListener('touchstart', function(event) {
      document.addEventListener('touchstart', preHandler, false); 
      that.drawBegin(event)
    })
    this.canvas.addEventListener('touchend', function(event) { 
      document.addEventListener('touchend', preHandler, false); 
      that.drawEnd()
      
    })
    this.clear(btn)
  }
  drawBegin(e) {
    var that = this;
    window.getSelection() ? window.getSelection().removeAllRanges() : document.selection.empty()
    this.cxt.strokeStyle = "#000"
    this.cxt.beginPath()
    this.cxt.moveTo(
      e.changedTouches[0].clientX - this.stage_info.left,
      e.changedTouches[0].clientY - this.stage_info.top
    )
    this.path.beginX = e.changedTouches[0].clientX - this.stage_info.left
    this.path.beginY = e.changedTouches[0].clientY - this.stage_info.top
    canvas.addEventListener("touchmove",function(){
      that.drawing(event)
    })
  }
  drawing(e) {
    this.cxt.lineTo(
      e.changedTouches[0].clientX - this.stage_info.left,
      e.changedTouches[0].clientY - this.stage_info.top
    )
    this.path.endX = e.changedTouches[0].clientX - this.stage_info.left
    this.path.endY = e.changedTouches[0].clientY - this.stage_info.top
    this.cxt.stroke()
  }
  drawEnd() {
    document.removeEventListener('touchstart', preHandler, false); 
    document.removeEventListener('touchend', preHandler, false);
    document.removeEventListener('touchmove', preHandler, false);
    //canvas.ontouchmove = canvas.ontouchend = null
  }
  clear(btn) {
    this.cxt.clearRect(0, 0, 300, 600)
  }
  save(){
    return canvas.toDataURL("image/png")
  }
}
export default {
 data () {
  return {
   msg: 'Welcome to Your Vue.js App',
   val:true,
   url:""
  }
 },
 mounted() {
   draw=new Draw('canvas');
   draw.init();
 },
 methods:{
  clear:function(){
    draw.clear();
  },
  save:function(){
    var data=draw.save();
    this.url = data;
    console.log(data)
  },
   mutate(word) {
     this.$emit("input", word);
   },
} 
} 
</script> 
<!-- Add "scoped" attribute to limit CSS to this component only --> 
<style scoped>
h1, h2 {
 font-weight: normal;
}
ul {
 list-style-type: none;
 padding: 0;
}
li {
 display: inline-block;
 margin: 0 10px;
}
a {
 color: #42b983;
}
#canvas {
 background: pink;
 cursor: default;
}
#keyword-box {
 margin: 10px 0;
}
</style>
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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