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微信小程序--实现canvas绘图并且可以复盘回看

2019-6-24 释然 前端及开发文章及欣赏


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目录结构:



index.wxml:

<view class="canvasBox">
  <canvas canvas-id="myCanvas" class="myCanvas" catchtouchstart='canvasStart' catchtouchmove='canvasMoving'></canvas>
</view>
<view class="btn">
  <button type="warn" bindtap='drawPen'>画笔</button>
  <button type="primary" bindtap='clearCanvas'>清空画板</button>
  <button type="warn" bindtap='clearLine'>橡皮擦</button>
  <button style='background:#000;color:#fff;' bindtap="black">黑色</button>
  <button style='background:yellow;color:#000;' bindtap="yellow">黄色</button>
  <button style='background:red;color:#fff;' bindtap="red">红色</button>
  <button style='background:blue;color:#fff;' bindtap="blue">蓝色</button>
  <button style='background:green;color:#fff;' bindtap="green">绿色</button>
  <button type="warn" bindtap="startRecording">开始录制</button>
  <button type="primary" bindtap='rePlay'>复盘</button>
  <button></button>
</view>
index.wxss:

.canvasBox{
  position: relative;
  top:0;
  left:0;
  width: 750rpx;
  height:800rpx;
  background:#eee;
}
.canvasBox .myCanvas{
  width: 100%;
  height:100%;
  position: absolute;
  top:0;
  left:0;
}
 
.btn{
  width: 750rpx;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
}
.btn button{
  width: 180rpx;
  font-size: 24rpx;
}
index.js:

//index.js
//获取应用实例
import {hisData} from "../../utils/historyOperation.js";
const app = getApp()
var moveToX = 0, moveToY = 0, lineToX = 0, lineToY = 0;
var context = null;
var isStart = false;
var date;
var startDate;//开始时刻
var penType = "drawPen";
var colorStr = "#000";
var operationType = "mapping";
Page({
  data: {
    
  },
  
  canvasStart:function(e){
    var x = Math.floor(e.touches[0].clientX);
    var y = Math.floor(e.touches[0].clientY);
    date = new Date();
    moveToX = x;
    moveToY = y;
    operationType = "mapping";
    if(penType === "clearPen"){
      operationType = "clearLine";
    }
    if (isStart) {
      hisData.hisDataArr.push({
        time: date.getTime() - startDate,
        operation: operationType,
        lineArr: {
          startX: moveToX,
          startY: moveToY,
          currentX: x,
          currentY: y,
          z: 1,
          colorStr:colorStr
        }
      })
    }
  },
  //绘制线条
  canvasMoving:function(e){
    date = new Date();
    var x = Math.floor(e.changedTouches[0].clientX);
    var y = Math.floor(e.changedTouches[0].clientY);
    lineToX = x;
    lineToY = y;
    if(penType === "clearPen"){
      operationType = "clearLine";
      context.clearRect(x-12, y-12, 24, 24);
      context.draw(true);
    }else{
      operationType = "mapping";
      context.setStrokeStyle(colorStr);
      context.moveTo(moveToX, moveToY);
      context.lineTo(lineToX, lineToY);
    }
    if (isStart) {
      hisData.hisDataArr.push({
        time: date.getTime() - startDate,
        operation: operationType,
        lineArr: {
          startX: moveToX,
          startY: moveToY,
          currentX: lineToX,
          currentY: lineToY,
          z: 1,
          colorStr: colorStr
        }
      })
    }
    moveToX = lineToX;
    moveToY = lineToY;
    context.stroke();
    context.draw(true);
  },
  
  clearCanvas:function(){
    context.clearRect(0,0,375,400);
    context.draw(true);
    date = new Date();//记录当前操作时刻
    operationType = "clearCanvas";
    if(isStart){
      hisData.hisDataArr.push({
        time: date.getTime() - startDate,
        operation: operationType,
        lineArr: {
          startX: -1,
          startY: -1,
          currentX: -1,
          currentY: -1,
          z: 0,
          colorStr: colorStr
        }
      })
    }
  },
  
  drawPen:function(){
    penType = "drawPen";
  },
  clearLine:function(){
    penType = "clearPen";
  },
  black:function(){
    colorStr = "#000";
  },
  yellow: function () {
    colorStr = "yellow";
  },
  red: function () {
    colorStr = "red";
  },
  blue: function () {
    colorStr = "blue";
  },
  green: function () {
    colorStr = "green";
  },
  startRecording:function(){
    isStart = true;
    date = new Date();
    startDate = date.getTime();
  },
  rePlay:function(){
    wx.navigateTo({
      url: '../replay/replay',
    })
  },
  onLoad: function () {
    isStart = false;
    context = wx.createCanvasContext('myCanvas');
    context.beginPath();
    context.setStrokeStyle('#000');
    context.setLineWidth(5);
    context.setLineCap('round');
    context.setLineJoin('round');
  }
})
historyOperation.js:该文件用来保存历史操作,以便复盘

const hisData = {
  hisDataArr:[
    {
      time:0,//操作时间
      /**
       * 操作类型
       * 绘图:mapping
       * 拖动球员:moveplayer
       * 清除画布:clearCanvas
       * 橡皮擦:clearLine
       */
      operation:"mapping",//操作类型
      /**
       * 绘制路径
       * startX:开始x坐标
       * startY:开y纵坐标
       * currentX:目标位置的 x 坐标
       * currentY:目标位置的 y 坐标
       * z:1代表画线时鼠标处于move状态,0代表处于松开状态
       * colorStr:线的填充颜色
       */
      lineArr: {    //绘制路径
        startX:0,
        startY:0,
        currentX:0,
        currentY:0,
        z:0,
        colorStr:"#000"
      }
    }
  ]
};
 
export {hisData};
复盘:

reply.wxml:

<!--pages/replay/replay.wxml-->
<view class="replayBox">
  <canvas canvas-id='myCanvas' class="myCanvas"></canvas>
</view>
<button type="warn" bindtap="start">开始</button>
reply.wxss:

/* pages/replay/replay.wxss */
.replayBox{
  position:relative;
  width: 750rpx;
  height:800rpx;
  background: #eee;
}
 
.replayBox .myCanvas{
  position: absolute;
  top:0;
  left:0;
  width:100%;
  height:100%;
}
 
reply.js:

// pages/replay/replay.js
import {hisData} from "../../utils/historyOperation.js";
var startDate;
var date;
var curTime;
var context = null;
var timer = null;
Page({
 
  /**
   * 页面的初始数据
   */
  data: {
 
  },
  start:function(){
    context.clearRect(0, 0, 375, 400);
    clearInterval(timer);
    date = new Date();
    startDate = date.getTime();
    var i = 0;
    var that = this;
    var len = hisData.hisDataArr.length;
    timer = setInterval(function(){
      date = new Date();
      curTime = date.getTime() - startDate;
      if (curTime >= hisData.hisDataArr[i].time){
        switch (hisData.hisDataArr[i].operation) {
          case "mapping":
            context.setStrokeStyle(hisData.hisDataArr[i].lineArr.colorStr);
            context.moveTo(hisData.hisDataArr[i].lineArr.startX, hisData.hisDataArr[i].lineArr.startY);
            context.lineTo(hisData.hisDataArr[i].lineArr.currentX, hisData.hisDataArr[i].lineArr.currentY);
            context.stroke();
            context.draw(true);
            break;
          case "clearCanvas":
            context.clearRect(0, 0, 375, 400);
            context.draw(true);
            break;
          case "clearLine":
            context.clearRect(hisData.hisDataArr[i].lineArr.currentX-12, hisData.hisDataArr[i].lineArr.currentY-12, 24, 24);
            context.draw(true);
            break;
        }
        i++;
      }
      if(i >= len){
        clearInterval(timer);
      }
    },2);
  },
  /**
   * 生命周期函数--监听页面加载
   */
  onLoad: function (options) {
    context = wx.createCanvasContext('myCanvas');
    context.beginPath();
    context.setStrokeStyle('#000');
    context.setLineWidth(3);
    context.setLineCap('round');
    context.setLineJoin('round');
  }
})
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