手势解锁是app上常见的解锁方式，相比输入密码方式操作起来要方便许多。下面展示如何基于微信小程序实现手机解锁。最终实现效果如下图:

整个功能基于canvas实现，首先添加画布组件，并设定样式

<!--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);
  }

源码地址:https://github.com/zjxfly/wx-gesture-lock/