<template>
 <div id="app">
  <div class="icon-add-50" :style="iconstyle" @click='click' @touchmove='touchmove' @touchstart='touchstart(this,$event)' @touchend='touchend'></div>
 </div>
</template>
<script>
export default {
 name: 'App',
 data(){
  return{
   /*--------图标样式变量--------------*/
   iconrotate:45,//旋转deg
   icontranslateX:100,//沿x轴位移px
   icontranslateY:100,//沿y轴位移px
   /*--------拖动计算变量------------*/
   mouseX:0,
   mouseY:0,
   objX:0,
   objY:0,
   isDown:false
  }
 },
 methods:{
  click:function(){//图标点击事件
   if (this.iconrotate==0) {
     this.iconrotate=315;
   }else {
    this.iconrotate=0;
   }
  },
  touchstart:function(obj,e){//finger touch 触发
   this.objX = this.icontranslateX;
   this.objY = this.icontranslateY;
   this.mouseX = e.touches[0].clientX;
   this.mouseY = e.touches[0].clientY;
   this.isDowm = true;
  },
  touchmove:function(e){//finger move 触发
   let x = e.touches[0].clientX;
   let y = e.touches[0].clientY;
   if (this.isDowm) {
     this.icontranslateX = parseInt(x) - parseInt(this.mouseX) + parseInt(this.objX);
     this.icontranslateY = parseInt(y) - parseInt(this.mouseY) + parseInt(this.objY);
   }
  },
  touchend:function(e){//finger from touch to notouch
   if (this.isDowm) {
     let x = e.touches[0].clientX;
     let y = e.touches[0].clientY;
     this.icontranslateX = parseInt(x) - parseInt(this.mouseX)+ parseInt(this.objX);
     this.icontranslateY = parseInt(y) - parseInt(this.mouseY)+ parseInt(this.objY);
     this.isDowm=false;
   }
  }
 },
 computed:{
  iconstyle:function(){//图标动态样式
   let arr = new Array();
   arr.push('transform:');//注意：先移动后旋转，实现原地旋转；先旋转后移动，位置按照旋转后的新坐标系确定
   arr.push('translateX('+this.icontranslateX+'px) ');
   arr.push('translateY('+this.icontranslateY+'px) ');
   arr.push('rotate('+this.iconrotate+'deg) ');
   return arr.join("");
  }
 }
}
</script>
<style>
#app {
 font-family: 'Avenir', Helvetica, Arial, sans-serif;
 -webkit-font-smoothing: antialiased;
 -moz-osx-font-smoothing: grayscale;
 text-align: center;
 color: #2c3e50;
 margin-top: 60px;
}
 /*加号*/
.icon-add-50{
  position: relative;
  box-sizing: border-box;
  width: 50px;
  height: 50px;
  border: 2px solid gray;
  border-radius: 50%;
  box-shadow:darkgrey 0px 0px 2px 2px;
  background-color: CornflowerBlue;
}
.icon-add-50:before{
  content: '';
  position: absolute;
  width: 30px;
  height: 2px;
  left: 50%;
  top: 50%;
  margin-left: -15px;
  margin-top: -1px;
  background-color: white;
}
.icon-add-50:after{
  content: '';
  position: absolute;
  width: 2px;
  height: 30px;
  left: 50%;
  top: 50%;
  margin-left: -1px;
  margin-top: -15px;
  background-color: white;
}
</style>