基于vue实现移动端圆形旋钮插件效果

更新时间：2020-08-06 21:24:02 作者：startmvc

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

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：