JS前端使用Canvas快速实现手势解锁特效

<div class="starMap" ref="starMap">
  <canvas
      id="starMap"
      ref="canvas"
      class="canvasBox"
      :width="width"
      :height="height"
      :style="{ width, height }"
      @touchstart="touchStart"
      @touchmove="touchMove"
      @touchend="touchEnd"
      @mousedown="touchStart"
      @mousemove="touchMove"
      @mouseup="touchEnd"
      @mouseout="touchEnd"
      @mouseenter="touchStart"
  ></canvas>
  <div class="starsList">
    <div v-for="n in starXNum" :key="n" class="starColBox" :style="{ marginBottom: `${spaceY}px` }">
      <div v-for="j in starYNum" :key="j" class="starRow" :style="{ marginRight: `${spaceX}px` }">
        <div :class="['starIcon', showStar(n, j) && 'show']" :style="{ width: `${starX}px`, height: `${starX}px` }">
          <div :class="['starCenter', isSelectedStar(n, j) && `animate-${getRandom(0, 2, 0)}`]"></div>
        </div>
      </div>
    </div>
  </div>
  <canvas id="judgeCanvas" :width="width" :height="height" class="judgeCanvas" :style="{ width, height }"></canvas>
</div>

/*
 * this.width=画布宽 
 * this.height=画布高
 * this.starX=星星的大小，宽高相等不做区分
*/
spaceX () { // 星星横向间距
  return (this.width - this.starX * this.starXNum) / 4
}
spaceY () { // 星星纵向间距
  return (this.height - this.starX * this.starYNum) / 4
}

function setData () { // 初始化canvas数据
  this.initStarPos()
  this.lineWidth = 2 // 连接线宽度
  this.lineBlurWidth = 6 // 连接线shadow宽
  this.canvas = document.getElementById('starMap')
  if (!this.canvas) return console.error('starMap: this.canvas is null')
  this.ctx = this.canvas.getContext('2d')
  this.ctx.strokeStyle = '#c9b8ff'
  this.ctx.lineCap = 'round'
  this.ctx.lineJoin = 'bevel'
  const judgeCanvas = document.getElementById('judgeCanvas')
  this.judgeCtx = judgeCanvas.getContext('2d')
}
function initStarPos () { // 初始化星星位置
  const arr = this.pointIndexArr = this.initPointShowArr()
  const pointPos = []
  /**
   * spaceX=横向间距；spaceY：纵向间距
   * 星星中点x位置: 星星/2 + (星星的尺寸 + 横向间距）* 前面的星星数量
   * 星星中点y位置: 星星/2 + (星星的尺寸 + 竖向间距）* 前面的星星数量
   * pointPos=所有页面渲染的星星(x, y)坐标
   */
  arr.forEach(item => {
    let x = 0
    let y = 0
    x = this.starX / 2 + (this.starX + this.spaceX) * (item % this.starXNum)
    y = this.starX / 2 + (this.starX + this.spaceY) * Math.floor(item / this.starXNum)
    pointPos.push({ x, y, index: item })
  })
  this.pointPos = [...pointPos]
}
function initPointShowArr () {
  const result = []
  const originArr = []
  const arrLen = getRandom(25, this.starXNum * this.starYNum, 0) // 可选择随机选择需要显示星星的数量 getRandom(21, 25, 0)
  const starOriginLen = this.starXNum * this.starYNum
  for (let i = 0; i < starOriginLen; i++) {
    originArr.push(i)
  }
  // 获取星星展示随机数组后进行排序重组
  for (let i = 0; i < arrLen; i++) {
    const random = Math.floor(Math.random() * originArr.length)
    if (result.includes(originArr[random])) {
      continue
    }
    result.push(originArr[random])
    originArr.splice(random, 1)
  }
  result.sort((a, b) => a - b)
  return result
}

function touchStart (e) {
  if (this.checkLimit()) return
  this.lockScroll()
  const rect = this.$refs.canvas.getBoundingClientRect() // 此处获取canvas位置，防止页面滚动时位置发生变化
  this.canvasRect = { x: rect.left, y: rect.top, left: rect.left, right: rect.right, bottom: rect.bottom, top: rect.top }
  const [x, y] = this.getEventPos(e)
  const index = this.indexOfPoint(x, y)
  if (this.pointsLen) {
    this.reconnectStart = true
  } else {
    this.pushToPoints(index)
  }
}
function getEventPos (event) { // 当前触摸坐标点相对canvas画布的位置
    const x = event.clientX || event.touches[0].clientX
    const y = event.clientY || event.touches[0].clientY
    return [x - this.canvasRect.x, y - this.canvasRect.y]
}
function indexOfPoint (x, y) {
  if (this.pointPos.length === 0) throw new Error('未找到星星坐标')
  // 为了减少计算量，将星星当初正方形计算
  for (let i = 0; i < this.pointPos.length; i++) {
    if ((Math.abs(x - this.pointPos[i].x) < this.starX / 1.5) && (Math.abs(y - this.pointPos[i].y) < this.starX / 1.5)) {
      return i
    }
  }
  return -1
}
function pushToPoints (index) {
  if (index === -1 || this.points.includes(index)) return false
  this.points.push(index)
  return true
}
function checkBeyondCanvas (e) { // 校验手指是否超出canvas区域
  const x = e.clientX || e.touches[0].clientX
  const y = e.clientY || e.touches[0].clientY
  const { left, top, right, bottom } = this.canvasRect
  const outDistance = 40 // 放宽边界的判断
  if (x < left - outDistance || x > right + outDistance || y < top - outDistance || y > bottom + outDistance) {
    this.connectEnd()
    return true
  }
  return false
}

  canvas.beginPath() // 表示开始画线或重置当前路径
  canvas.moveTo(x, y) // 指定目标路径的开始位置，不创建线条
  canvas.lineTo(x, y) // 添加一个新点，创建从该点到画布中最后指定点的线条，不创建线条
  canvas.closePath() // 结束路径，应与开始路径呼应
  canvas.stroke() // 实际地绘制出通过 moveTo() 和 lineTo() 方法定义的路径，默认为黑色
  const grd = canvas.createLinearGradient(x1, y1, x2, y2) // 创建线性渐变的起止坐标
  grd.addColorStop(0, '#c9b8ff') // 定义从 0 到 1 的颜色渐变
  grd.addColorStop(1, '#aa4fff')
  canvas.strokeStyle = grd

function touchMove (e) {
  console.log('touchMove', e)
  if (this.checkBeyondCanvas(e)) return // 防止touchmove移出canvas区域后不松手，滚动后页面位置改变在canvas外其他位置触发连接
  if (this.checkLimit()) return
  this.lockScroll() // 手指活动过程中禁止页面滚动
  const [x, y] = this.getEventPos(e)
  const idx = this.indexOfPoint(x, y)
  if (this.reconnectStart && (idx === this.points[this.pointsLen - 1] || idx !== this.points[0])) {
    this.reconnectStart = false
    idx === this.points[0] && this.points.reverse()
  }
  this.pushToPoints(idx)
  this.draw(x, y)
}
function draw (x, y) {
  if (!this.canvas) return
  this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height)
  if (this.pointsLen === 0) return
  this.rearrangePoints(x, y)
  this.drawLine(x, y)
}
function drawLine (x, y) {
  this.ctx.lineWidth = this.lineWidth
  const startPos = this.getPointPos(0)
  const endPos = this.getPointPos(this.pointsLen - 1)
  for (let i = 1; i < this.pointsLen; i++) {
    const movePos = i === 1 ? startPos : this.getPointPos(i - 1)
    this.drawradientLine(movePos.x, movePos.y, this.getPointPos(i).x, this.getPointPos(i).y, true)
  }
  if (x !== undefined && y !== undefined) {
    this.drawradientLine(endPos.x, endPos.y, x, y, false)
  } else {
    this.ctx.stroke()
  }
}
drawradientLine (x1, y1, x2, y2, closePath) { // 渐变线条
  if (!this.ctx) return
  this.ctx.beginPath()
  this.ctx.moveTo(x1, y1) // 开始位置
  this.ctx.lineTo(x2, y2) // 画到此处
  const grd = this.ctx.createLinearGradient(x1, y1, x2, y2) // 线性渐变的起止坐标
  grd.addColorStop(0, '#c9b8ff')
  grd.addColorStop(1, '#aa4fff')
  this.ctx.strokeStyle = grd
  this.ctx.shadowBlur = this.lineBlurWidth
  this.ctx.shadowColor = '#5a00ff'
  closePath && this.ctx.closePath() 
  this.ctx.stroke()
}

function touchEnd (e) {
  this.connectEnd(true)
}
connectEnd () {
  this.unlockScroll()
  if (this.pointsLen === 1) {
    this.points = []
  }
  this.draw()
  if (this.pointsLen > 1 && this.pointsLen < this.minLength && !this.reconnectStart) {
    this.showToast(`至少连接${this.minLength}颗星星哦～`)
  }
}

function lockScroll () {
  if (this.unlock) return
  this.unlock = lockScrollFunc()
}
function unlockScroll () {
  if (this.unlock) {
    this.unlock()
    this.unlock = null
  }
}
function unLockScrollFunc () {
  const str = document.body.getAttribute(INTERNAL_LOCK_KEY)
  if (!str) return
  try {
    const { height, pos, top, left, right, scrollY } = JSON.parse(str)
    document.documentElement.style.height = height
    const bodyStyle = document.body.style
    bodyStyle.position = pos
    bodyStyle.top = top
    bodyStyle.left = left
    bodyStyle.right = right
    window.scrollTo(0, scrollY)
    setTimeout(() => {
      document.body.removeAttribute(LOCK_BODY_KEY)
      document.body.removeAttribute(INTERNAL_LOCK_KEY)
    }, 30)
  } catch (e) {}
}
function lockScrollFunc () {
  if (isLocked) return unLockScrollFunc
  const htmlStyle = document.documentElement.style
  const bodyStyle = document.body.style
  const scrollY = window.scrollY
  const height = htmlStyle.height
  const pos = bodyStyle.position
  const top = bodyStyle.top
  const left = bodyStyle.left
  const right = bodyStyle.right
  bodyStyle.position = 'fixed'
  bodyStyle.top = -scrollY + 'px'
  bodyStyle.left = '0'
  bodyStyle.right = '0'
  htmlStyle.height = '100%'
  document.body.setAttribute(LOCK_BODY_KEY, scrollY + '')
  document.body.setAttribute(INTERNAL_LOCK_KEY, JSON.stringify({
    height, pos, top, left, right, scrollY
  }))
  return unLockScrollFunc
}

 canvas.isPointInPath(x, y) // 判断点 (x, y)是否在canvas路径的区域内

function rearrangePoints () { // 根据最后两个点之间连线，如果有多出的点进行重排，否则不处理
  if (this.pointsLen === 1) return
  const endPrevPos = this.getPointPos(this.pointsLen - 2)
  const endPos = this.getPointPos(this.pointsLen - 1)
  const x1 = endPrevPos.x
  const y1 = endPrevPos.y
  const x2 = endPos.x
  const y2 = endPos.y
  this.judgeCtx.beginPath()
  this.judgeCtx.moveTo(x1, y1) // 开始位置
  this.judgeCtx.lineTo(x2, y2) // 画到此处
  const extraArr = []
  const realArr = []
  this.pointPos.forEach((item, i) => {
    if (this.judgeCtx.isPointInStroke(item.x, item.y)) realArr.push(i)
    if (this.judgeCtx.isPointInStroke(item.x, item.y) && !this.points.includes(i)) {
      extraArr.push(i)
    }
  })
  if (!extraArr.length) return
  const extraPosArr = extraArr.map(item => {
    return { ...this.pointPos[item], i: item }
  })
  const getExtraSortMap = new Map([
    [[0, -1], (a, b) => a.y - b.y],
    [[0, 1], (a, b) => b.y - a.y],
    [[-1, 0], (a, b) => a.x - b.x],
    [[1, 0], (a, b) => b.x - a.x],
    [[-1, -1], (a, b) => (a.x - b.x) && (a.y - b.y)],
    [[1, 1], (a, b) => (b.x - a.x) && (b.y - a.y)],
    [[1, -1], (a, b) => (b.x - a.x) && (a.y - b.y)],
    [[-1, 1], (a, b) => (a.x - b.x) && (b.y - a.y)]
  ])
  const extraSortArr = extraPosArr.sort(getExtraSortMap.get([this.getEqualVal(x1, x2), this.getEqualVal(y1, y2)]))
  this.points.splice(this.pointsLen - 1, 0, ...(extraSortArr.map(item => item.i)))
  this.pointsLen > this.maxLength && this.points.splice(this.maxLength, this.pointsLen - this.maxLength)
}
function getEqualVal (a, b) {
  return a - b === 0 ? 0 : a - b > 0 ? 1 : -1
}