微信小程序开发之手势解锁的介绍

<!--index.wxml-->
<view class="container">
 <canvas canvas-id="id-gesture-lock" class="gesture-lock" bindtouchstart="onTouchStart"
  bindtouchmove="onTouchMove" bindtouchend="onTouchEnd"></canvas>
</view>

.gesture-lock {
  margin: 100rpx auto;
  width: 300px;
  height: 300px;
  background-color: #ffffff;
}
手势解锁实现代码在gesture_lock.js中(完整源码地址见末尾)。
初始化
  constructor(canvasid, context, cb, opt){
    this.touchPoints = [];
    this.checkPoints = [];
    this.canvasid = canvasid;
    this.ctx = context;
    this.width = opt && opt.width    300; //画布长度
    this.height = opt && opt.height    300; //画布宽度
    this.cycleNum = opt && opt.cycleNum    3;
    this.radius = 0; //触摸点半径
    this.isParamOk = false;
    this.marge = this.margeCircle = 25; //触摸点及触摸点和画布边界间隔
    this.initColor = opt && opt.initColor    '#C5C5C3';  
    this.checkColor = opt && opt.checkColor    '#5AA9EC';
    this.errorColor = opt && opt.errorColor    '#e19984';
    this.touchState = "unTouch";
    this.checkParam();
    this.lastCheckPoint = null;
    if (this.isParamOk) {
      // 计算触摸点的半径长度
      this.radius = (this.width - this.marge * 2 - (this.margeCircle * (this.cycleNum - 1))) / (this.cycleNum * 2)
      this.radius = Math.floor(this.radius);
      // 计算每个触摸点的圆心位置
      this.calCircleParams();
    }
    this.onEnd = cb; //滑动手势结束时的回调函数
  }
主要设置一些参数，如canvas的长宽，canvas的context，手势锁的个数(3乘3, 4乘4)，手势锁的颜色，手势滑动结束时的回调函数等。并计算出手势锁的半径。
计算每个手势锁的圆心位置
  calCircleParams() {
    let n = this.cycleNum;
    let count = 0;
    for (let i = 0; i < n; i++) {
      for (let j = 0; j < n; j++){
        count++;
        let touchPoint = {
          x: this.marge + i * (this.radius * 2 + this.margeCircle) + this.radius,
          y: this.marge + j * (this.radius * 2 + this.margeCircle) + this.radius,
          index: count,
          check: "uncheck",
        }
        this.touchPoints.push(touchPoint)
      }
    }
  }
绘制手势锁
   for (let i = 0; i < this.touchPoints.length; i++){
      this.drawCircle(this.touchPoints[i].x, this.touchPoints[i].y, this.radius, this.initColor)
   }
   this.ctx.draw(true);
接下来就是识别用户的滑动行为，判断用户划过了哪些圆圈，进而识别出用户的手势。
在touchstart和touchmove事件中检测触发并更新画布
  onTouchStart(e) {
    // 不识别多点触控
    if (e.touches.length > 1){
      this.touchState = "unTouch";
      return;
    }
    this.touchState = "startTouch";
    this.checkTouch(e);
    let point = {x:e.touches[0].x, y:e.touches[0].y};
    this.drawCanvas(this.checkColor, point);
  }

  onTouchMove(e) {
    if (e.touchState === "unTouch") {
      return;
    }
    if (e.touches.length > 1){
      this.touchState = "unTouch";
      return;
    }
    this.checkTouch(e);
    let point = {x:e.touches[0].x, y:e.touches[0].y};
    this.drawCanvas(this.checkColor, point);
  }
检测用户是否划过某个圆圈
  checkTouch(e) {
    for (let i = 0; i < this.touchPoints.length; i++){
      let point = this.touchPoints[i];
      if (isPointInCycle(e.touches[0].x, e.touches[0].y, point.x, point.y, this.radius)) {
        if (point.check === 'uncheck') {
          this.checkPoints.push(point);
          this.lastCheckPoint = point;
        }
        point.check = "check"
        return;
      }
    }
  }
更新画布
   drawCanvas(color, point) {
    //每次更新之前先清空画布
    this.ctx.clearRect(0, 0, this.width, this.height);
    //使用不同颜色和形式绘制已触发和未触发的锁
    for (let i = 0; i < this.touchPoints.length; i++){
      let point = this.touchPoints[i];
      if (point.check === "check") {
        this.drawCircle(point.x, point.y, this.radius, color);
        this.drawCircleCentre(point.x, point.y, color);
      }
      else {
        this.drawCircle(this.touchPoints[i].x, this.touchPoints[i].y, this.radius, this.initColor)
      }
    }
    //绘制已识别锁之间的线段
    if (this.checkPoints.length > 1) {
       let lastPoint = this.checkPoints[0];
       for (let i = 1; i < this.checkPoints.length; i++) {
         this.drawLine(lastPoint, this.checkPoints[i], color);
         lastPoint = this.checkPoints[i];
       }
    }
    //绘制最后一个识别锁和当前触摸点之间的线段
    if (this.lastCheckPoint && point) {
      this.drawLine(this.lastCheckPoint, point, color);
    }
    this.ctx.draw(true);
  }
当用户滑动结束时调用回调函数并传递识别出的手势
  onTouchEnd(e) {
    typeof this.onEnd === 'function' && this.onEnd(this.checkPoints, false);
  }

  onTouchCancel(e) {
    typeof this.onEnd === 'function' && this.onEnd(this.checkPoints, true);
  }
重置和显示手势错误
  gestureError() {
    this.drawCanvas(this.errorColor)
  }

  reset() {
    for (let i = 0; i < this.touchPoints.length; i++) {
      this.touchPoints[i].check = 'uncheck';
    }
    this.checkPoints = [];
    this.lastCheckPoint = null;
    this.drawCanvas(this.initColor);
  }
如何调用 
在onload方法中创建lock对象并在用户触摸事件中调用相应方法
 onLoad: function () {
  var s = this;
  this.lock = new Lock("id-gesture-lock", wx.createCanvasContext("id-gesture-lock"), function(checkPoints, isCancel) {
   console.log('over');
   s.lock.gestureError();
   setTimeout(function() {
    s.lock.reset();
   }, 1000);
  }, {width:300, height:300})
  this.lock.drawGestureLock();
  console.log('onLoad')
  var that = this
  //调用应用实例的方法获取全局数据
  app.getUserInfo(function(userInfo){
   //更新数据
   that.setData({
    userInfo:userInfo
   })
   that.update()
  })
 },
 onTouchStart: function (e) {
  this.lock.onTouchStart(e);
 },
 onTouchMove: function (e) {
  this.lock.onTouchMove(e);
 },
 onTouchEnd: function (e) {
  this.lock.onTouchEnd(e);
 }
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小程序是一种不需要下载安装即可使用的应用，它实现了应用“触手可及”的梦想，用户扫一扫或者搜一下即可打开应用。



  
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