在canvas中如何實現軌跡回放功能

這篇文章主要介紹了canvas軌跡回放功能實現過程以及相關的程式碼整理

本文透過json機構，HTML程式碼以及JS程式碼詳細給大家分析了canvas軌跡回放功能實現的過程，以下是全部內容。

json結構

[
  {
    "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

將json當作js檔案引入，並將其賦值給全域變數testPath(引入方式按照實際專案要求來)

<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=&#39;test&#39; width="600" height="200"></canvas>
<script type="text/javascript" src=&#39;js/jquery-2.1.4.min.js&#39;></script>
<script type="text/javascript" src=&#39;js/number.js&#39;></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();
});

上面是我整理給大家的，希望未來會對大家有幫助。

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