JS 简单实现拖拽评星的示例代码
作者:头疼脑胀的代码搬运工
本文主要介绍了JS 简单实现拖拽评星,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧
废话开篇:通过 canvas 简单拖拽评星,主要是通过个人的理解去实现这样的一个效果。
一、实现效果
html
<div class="main"> <div class="score_container"> <canvas id="canvas" height="100"></canvas> <div id="score" class="score">评分:0</div> </div> </div>
css
.main { display: flex; flex-direction: row; justify-content: start; align-items: flex-start; padding-top: 20px; padding-left: 20px; } .score_container { display: flex; flex-direction: column; justify-content: center; align-items: center; padding-top: 20px; } .score { margin-top: 20px; }
js
// 星星数据对象 class Pentagram{ points = [] minX = 0 maxX = 0 deg = (Math.PI / 180) score = 0 constructor(index,r,center){ this.savePentagramData(index,r,center) } // 绘制星星 savePentagramData(currentPentagramIndex,r,{x,y}){ // 它对应的整数分数 this.score = currentPentagramIndex + 1 // 工具函数 let cos = (d)=>{ return Math.cos(d * this.deg) } let sin = (d)=>{ return Math.sin(d * this.deg) } let tan = (d)=>{ return Math.tan(d * this.deg) } let square = (num)=> { return Math.pow(num,2) } // 外边比例 let t = 1 / ((1 + square(tan(18))) / (3 - square(tan(18)))) this.points = [ [0,1], [t*cos(54),t*sin(54)], [cos(18),sin(18)], [t*cos(18),-t*sin(18)], [cos(54),-sin(54)], [0,-t], [-cos(54),-sin(54)], [-t*cos(18),-t*sin(18)], [-cos(18),sin(18)], [-t*cos(54),t*sin(54)], [0,1], ] this.points.forEach((point,index)=>{ point[0] = x + point[0] * (r / t) point[1] = y + point[1] * (r / t) if(index == 7) { // 最右侧的点 this.minX = point[0] } if(index == 3) { // 最左侧的点 this.maxX = point[0] } }) } } // 星星管理器 class PentagramManage{ canvas = null//画板相关 context = null pentagramNum = 1//星星个数 isMouseDown = false//鼠标是否按下 progress = 0//当前评分位置 pentagramRadius = 15//星星半径 pentagramSep = 10//星星间间隔 pentagrams = []//记录每一个星星对象 constructor(pentagramNum){ this.pentagramNum = pentagramNum this.initData() this.draw() this.bindMouseEvent() } // 初始化 initData(){ this.canvas = document.getElementById('canvas') for(let i = 0;i < this.pentagramNum;i ++){ let pentagram = new Pentagram(i,this.pentagramRadius,{x:35 + i * (this.pentagramRadius * 2 + this.pentagramSep),y:(this.canvas.height / 2.0) }) this.pentagrams.push(pentagram) if(i == this.pentagramNum - 1){ this.canvas.width = pentagram.maxX + 20 } } this.context = this.canvas.getContext('2d'); this.context.fillStyle='white'; } //绘制 draw(){ this.context.clearRect(0,0,this.canvas.width,this.canvas.height); this.drawBottomPlate() let hook = ()=>{ this.pentagrams.forEach((pentagramItem)=>{ this.drawPentagram(pentagramItem) }) } this.drawHollowOut(hook) this.drawStrokeHollowOut(hook) } // 绘制底色 drawBottomPlate(){ this.context.save() this.context.fillStyle= 'rgb(247,190,80)'; this.context.beginPath(); this.context.rect(0, 0, this.progress, this.canvas.height); this.context.closePath(); this.context.fill(); this.context.restore() } // 绘制镂空五角星 drawHollowOut(hook){ this.context.beginPath(); this.context.rect(0, 0, this.canvas.width, this.canvas.height); hook() this.context.closePath(); this.context.fill(); } // 绘制五星边框 drawStrokeHollowOut(hook){ this.context.save(); this.context.strokeStyle = 'rgb(247,190,80)'; // this.context.stroke.width = 1 this.context.beginPath(); this.context.rect(0, 0, this.canvas.width, this.canvas.height); hook() this.context.closePath(); this.context.stroke(); this.context.restore(); } // 绘制星星 drawPentagram(pentagramItem){ pentagramItem.points.forEach((point,index)=>{ eval('this.context.' + (index == 0 ? 'moveTo(' : 'lineTo(') + '...point)') }) } // 绑定鼠标事件 bindMouseEvent(){ document.onmousemove = (event)=>{ if(this.isMouseDown){ let { left } = this.getElementPosition(document.getElementById('canvas')) this.progress = event.clientX - left this.draw() this.getCurrentScore() } } //鼠标按下事件 document.onmousedown = (event)=>{ this.isMouseDown = true let { left } = this.getElementPosition(document.getElementById('canvas')) this.progress = event.clientX - left this.draw() this.getCurrentScore() } //鼠标抬起事件 document.onmouseup = ()=>{ this.isMouseDown = false } } // 计算分数 getCurrentScore(){ let score = 0 let firstPentagram = this.pentagrams.find((pentagram)=>{ return this.progress <= pentagram.maxX }) if(firstPentagram){ let float = (Math.floor(((this.progress - firstPentagram.minX) / (firstPentagram.maxX - firstPentagram.minX)) * 10)) / 10 float = float > 0 ? float : 0 score = (firstPentagram.score - 1) + float document.getElementById('score').innerHTML = "评分:" + score } else { document.getElementById('score').innerHTML = "评分:" + this.pentagrams.length } } // dom在浏览器的位置 getElementPosition(element){ let top = element.offsetTop let left = element.offsetLeft let width = element.offsetWidth let height = element.offsetHeight var currentParent = element.offsetParent; while (currentParent !== null) { top += currentParent.offsetTop left += currentParent.offsetLeft currentParent = currentParent.offsetParent } return {top,left,width,height} } } var pentagram = new PentagramManage(4)
二、总结与思考
上层无镂空
上层有镂空
通过 canvas 实现一层镂空五角星层,再在底层添加一个进度层,这样在拖动的时候就能通过拖拽的位置进行数据处理,从而计算出星级数。代码拙劣,大神勿笑
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