基于vue实现移动端圆形旋钮插件效果

2019-11-19 12:27:08

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最近公司有一个项目的需要做出旋钮的效果，旋钮有十个档，根据手指旋转切换，旋转时接近最近的档会有吸附效果，具体效果如下：

html部分代码：

<div class="_touch"> <div class="round_box" ref="box" @touchstart="touchStart" @touchmove="touchMove">  <div v-if="able" style="position:absolute;width:100%;height:100%;top:0;left:0;">   <div class="round_right" ref="right" :style="{ transform: 'rotate(' + angle +'deg)' }">    <div class="round_info"></div>   </div>   <div class="round_num">{{level}}</div>  </div> </div></div>

less样式部分代码：

._touch { padding-top: 48px; .round_box {  position: relative;  width: 54%;  padding-top: 54%;  margin: 0 auto;  background-image: url(../../assets/img/round_box.png);  background-size: auto 100%;  background-position: center top;  background-repeat: no-repeat;  .round_right {   width: 8%;   height: 27%;   position: absolute;   left: 46%;   top: 23%;   transform-origin: 50% 100%;   -webkit-transform-origin: 50% 100%;   z-index: 2;   .round_info {    background: linear-gradient(#858585, #b3b3b3);    background: -webkit-gradient(#858585, #b3b3b3);    background: -moz-linear-gradient(#858585, #b3b3b3);    width: 100%;    padding-top: 100%;    border-radius: 100%;   }  }  .round_num {   display: inline-block;   position: absolute;   z-index: 1;   text-align: center;   width: 30%;   top: 38%;   left: 35%;   font-size: 2.4em;   font-weight: 900;   background: linear-gradient(#b0b0b0, #c8c8c8);   background: -webkit-gradient(#b0b0b0, #c8c8c8);   -webkit-background-clip: text;   background-clip: text;   -webkit-text-fill-color: transparent;   text-fill-color: transparent;  } }}

js部分代码：

methods: { ......, touchStart(e) {  e.preventDefault();  e.stopPropagation();  let round_box = this.$refs.box;  var w = round_box.offsetWidth / 2;  var h = round_box.offsetHeight / 2;  this.px = round_box.getBoundingClientRect().left + w;  this.py = round_box.getBoundingClientRect().top + h; }, touchMove(e) {  e.preventDefault();  e.stopPropagation();  this.getAngle(e.changedTouches[0].clientX, e.changedTouches[0].clientY); }, touchEnd(e) {  e.preventDefault();  e.stopPropagation(); }, resetAngle(angle) {  let list = [   { angle: 0, level: 5 },   { angle: 36, level: 6 },   { angle: 72, level: 7 },   { angle: 108, level: 8 },   { angle: 144, level: 9 },   { angle: 180, level: 10 },   { angle: 216, level: 1 },   { angle: 252, level: 2 },   { angle: 288, level: 3 },   { angle: 324, level: 4 },   { angle: 360, level: 5 }  ];  let result = list.filter(function(currentVal, index, arr) {   return Math.abs(angle - currentVal.angle) <= 18;  });  this.angle = result[0].angle;  this.level = result[0].level; }, getAngle(mx, my) {  var px = this.px;  var py = this.py;  var x = Math.abs(px - mx);  var y = Math.abs(py - my);  var z = Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2));  var cos = y / z;  var radina = Math.acos(cos); //用反三角函数求弧度  var angle = Math.floor(180 / (Math.PI / radina)); //将弧度转换成角度  if (mx > px && my > py) {   //鼠标在第四象限   angle = 180 - angle;  }  if (mx == px && my > py) {   //鼠标在y轴负方向上   angle = 180;  }  if (mx > px && my == py) {   //鼠标在x轴正方向上   angle = 90;  }  if (mx < px && my > py) {   //鼠标在第三象限   angle = 180 + angle;  }  if (mx < px && my == py) {   //鼠标在x轴负方向   angle = 270;  }  if (mx < px && my < py) {   //鼠标在第二象限   angle = 360 - angle;  }  this.angle = angle;  this.$nextTick(function() {   this.resetAngle(this.angle);  }); },......

主要的思路是根据监听 .round_box 元素的 touchmove 事件获取手指相对于圆心这条直线的旋转角度（transform : rotate），

并把旋转角度同步到水平居中于 .round_box 容器，底边框中心与 .round_box重合的元素： .round_right 上，使它相对于

.round_box的圆心旋转即可。

注：.round_box圆心如下：