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JS前端Canvas手势解锁

前端一叶子 人气:0

前言

之前在公司开发活动项目的时候,遇到一个项目需求要让用户使用手势画星位图来解锁星座运势,一看设计稿,这不就是我们平时的手机屏幕解锁吗?于是上网搜了一些关于手势解锁的文章,没找到可以直接复用的,于是只能自己打开canvas教程,边学习边设计实现了这个功能,同时兼容了移动端和PC端,在这里把代码分享出来,感兴趣的可以看看。

Demo

前往我的github查看源码

需要实现的功能

初始化数据和页面渲染

<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
}

初始化canvas画布和基础数据

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
}

touchstart 手指开始触摸事件

监听手指开始触摸事件:

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
}

touchmove 监听手指滑动事件

监听手指滑动事件:

drawLine中涉及到一些canvas的基本方法和属性:

  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()
}

touchend 监听手指触摸结束事件

手指离开屏幕时, 当前连接星星如果少于两颗(至少连接两个点),则清空数组,否则按照当前已连接的点重新绘制线条,当已连接的点小于最小限制时,给用户toast提示。

至此,连接星星的基本功能就完成了,还需要进行一些细节的处理。

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~`)
  }
}

页面滚动处理

当页面有滚动条是,连线过程中容易连带着页面滚动,导致触摸点错位,并且用户体验不好。解决方案是:每当手指触摸画布区域开始连接时,先禁止页面的滚动,当手指放开后或离开画布后再恢复页面滚动。

具体代码如下:

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
}

连接的两颗星星之间有其他星星时

如上所示,当连接的两颗星星路径上有其他的星星时,视觉上四连接了4颗星星,实际上中间两颗手指未触摸过的星星并未加入到当前绘制星星的数组中,这时候如果想要做最大最小星星数量的限制就会失误,因此这里通过判断方向,将中间两颗星星也接入到已连接星星数组中,每次 draw() 时判断一下。

如下列出了连接所有可能的8种情况和处理步骤:

判断是否有多余的点

判断方向 a.竖线: x1 = x2

给点数组重新排序

与points合并

长度超出最大限制个则从末尾抛出

开始画线

 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
}

最后找了个星空背景的demo贴到代码中,功能就完成了,关于星空背景的实现感兴趣的可以自己研究一下。

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