canvas轨迹回放功能实现

本文通过json机构，html代码以及js代码详细给大家分析了canvas轨迹回放功能实现的过程，以下是全部内容。

json结构

[
  {
    "path": [
      {
        "x": 82, 
        "y": 43
      }, 
      {
        "x": 83, 
        "y": 43
      }, 
      {
        "x": 84, 
        "y": 45
      }, 
      {
        "x": 86, 
        "y": 47
      }, 
      {
        "x": 86, 
        "y": 49
      }, 
      {
        "x": 86, 
        "y": 54
      }, 
      {
        "x": 86, 
        "y": 59
      }, 
      {
        "x": 86, 
        "y": 64
      }, 
      {
        "x": 86, 
        "y": 69
      }, 
      {
        "x": 86, 
        "y": 74
      }, 
      {
        "x": 86, 
        "y": 78
      }, 
      {
        "x": 86, 
        "y": 83
      }, 
      {
        "x": 86, 
        "y": 87
      }, 
      {
        "x": 86, 
        "y": 89
      }, 
      {
        "x": 86, 
        "y": 91
      }, 
      {
        "x": 86, 
        "y": 92
      }, 
      {
        "x": 86, 
        "y": 93
      }, 
      {
        "x": 86, 
        "y": 94
      }, 
      {
        "x": 86, 
        "y": 95
      }
    ]
  }, 
  {
    "path": [
      {
        "x": 129, 
        "y": 36
      }, 
      {
        "x": 129, 
        "y": 39
      }, 
      {
        "x": 129, 
        "y": 44
      }, 
      {
        "x": 129, 
        "y": 49
      }, 
      {
        "x": 129, 
        "y": 54
      }, 
      {
        "x": 129, 
        "y": 59
      }, 
      {
        "x": 128, 
        "y": 65
      }, 
      {
        "x": 127, 
        "y": 73
      }, 
      {
        "x": 125, 
        "y": 78
      }, 
      {
        "x": 125, 
        "y": 81
      }, 
      {
        "x": 124, 
        "y": 88
      }, 
      {
        "x": 123, 
        "y": 91
      }, 
      {
        "x": 123, 
        "y": 94
      }, 
      {
        "x": 123, 
        "y": 96
      }, 
      {
        "x": 123, 
        "y": 97
      }, 
      {
        "x": 123, 
        "y": 98
      }, 
      {
        "x": 123, 
        "y": 99
      }, 
      {
        "x": 122, 
        "y": 100
      }
    ]
  }
]

html

将json作为js文件引入，并将其赋值给全局变量testpath(引入方式按照实际项目要求来)

<style>
*{margin:0; padding:0;}
#test{border:1px solid #ccc; background: #eee; margin:20px 30px;}
</style>
<p><button id="start">start</button></p>
<canvas id='test' width="600" height="200"></canvas>
<script type="text/javascript" src='js/jquery-2.1.4.min.js'></script>
<script type="text/javascript" src='js/number.js'></script>

js

$('#start').click(function(event) {
  var lineindex = 0,pointindex = 0,line2;
  var obj = document.getelementbyid('test');
  var cxt = obj.getcontext('2d');
  cxt.linewidth = 1;
  cxt.strokestyle = 'red';
  cxt.linecap = 'round';
  cxt.clearrect(0,0,600,200);
  function drawbegin(){
    cxt.beginpath();
    pointindex=0;
    var intervalhandle = window.setinterval(function () {
      line2 = testpath[lineindex].path[pointindex];
      if (!line2) {
        window.clearinterval(intervalhandle);
        if (lineindex < testpath.length - 1) {
          lineindex = lineindex + 1;
          drawbegin();
        }
      }else{
        if (pointindex == 0) {
          cxt.moveto(line2.x, line2.y);
        }
        pointindex = pointindex + 1;
        cxt.lineto(line2.x, line2.y);
        cxt.stroke();
      }
    },0);
  }
  drawbegin();
});

以上就是本次文章的全部内容，如果大家在测试的时候还有什么疑问，可以在下方的留言区讨论。