Question

我有一个JSON文件，包含一堆我想慢慢绘制的点。我读过一个tutorial，但这只画了一行。但我想要的是按顺序绘制几条线（先画一条然后画另一条）并使用不同的起点。这是JSON文件：

{
  "data": [
    {
      "line": {
        "color": "#96c23b",
        "points": [
          {
            "x": 1,
            "y": 2
          },
          {
            "x": 2,
            "y": 3
          },
          {
            "x": 4,
            "y": 5
          },
          {
            "x": 7,
            "y": 8
          }
        ],
        "width": 2.0
      },
      "type": "line",
      "line_id": "1"
    },
    {
      "line": {
        "color": "#DF5453",
        "points": [
          {
            "x": 33,
            "y": 34
          },
          {
            "x": 34,
            "y": 35
          },
          {
            "x": 38,
            "y": 39
          },
          {
            "x": 40,
            "y": 42
          },
          {
            "x": 45,
            "y": 46
          }
        ],
        "width": 5.0
      },
      "type": "line",
      "line_id": "2"
    }
  ]
}

绘画速度无关紧要。

我知道如何解析JSON并在没有动画的情况下在画布中绘制线条。这是jQuery的代码：

var points_list =  {"data":[
  {"line":{"color":"#96c23b","points":[{"x":1,"y":2},{"x":2,"y":3},{"x":4,"y":5},{"x":7,"y":8}],"width":2.0},"type":"line","line_id":"1"},
  {"line":{"color":"#DF5453","points":[{"x":33,"y":34},{"x":34,"y":35},{"x":38,"y":39},{"x":40,"y":42},{"x":45,"y":46}],"width":5.0},"type":"line","line_id":"2"}
]}

function drawLines() {
    var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d");

    $.each(points_list.data, function (key, value) {
        var info = value.line;
        var color = info.color;
        var width = info.width;
        var points = info.points;

        context.beginPath();
        context.moveTo(points[0].x, points[0].y);
        context.lineWidth = width;
        context.strokeStyle = color;
        context.fillStyle = color;

        for (var p = 1; p < points.length; p++) {
            context.lineTo(points[p].x, points[p].y);
        }
        context.stroke();
    });
}

Answer 1

以下是使用变量跟踪outerList和innerList的位置的示例。使用lineIndexB跟踪外部列表（points_list.data），使用lineIndexA跟踪innerList（points_list.data.line.points）。

每次激活drawLines函数时，都会绘制下一个线段，然后增加lineIndexA变量。如果线段完成，则lineIndexB递增。

这是使用setTimeout函数使动画工作，它可以很容易地转换为requestAnimationFrame。

＆＃13;

var points_list =  {"data":[
  {"line":{"color":"#96c23b","points":[{"x":1,"y":2},{"x":2,"y":3},{"x":4,"y":5},{"x":7,"y":8}],"width":2.0},"type":"line","line_id":"1"},
  {"line":{"color":"#DF5453","points":[{"x":33,"y":34},{"x":34,"y":35},{"x":38,"y":39},{"x":40,"y":42},{"x":45,"y":46}],"width":5.0},"type":"line","line_id":"2"}
]};

var lineIndexA = 1;
var lineIndexB = 0;

var canvas = document.getElementById("canvas");
canvas.width = 500;
canvas.height = 500;
var context = canvas.getContext("2d");

function drawLines() {
   
	var value = points_list.data[lineIndexB];
  var info = value.line;
  var color = info.color;
  var width = info.width;
  var points = info.points;

  context.beginPath();
  context.moveTo(points[lineIndexA-1].x, points[lineIndexA-1].y);
  context.lineWidth = width;
  context.strokeStyle = color;
  context.fillStyle = color;
  context.lineTo(points[lineIndexA].x, points[lineIndexA].y);        
  context.stroke();
    
  lineIndexA = lineIndexA + 1;
  if (lineIndexA>points.length-1) {
  	lineIndexA = 1;
    lineIndexB = lineIndexB + 1;
  }
        
  //stop the animation if the last line is exhausted...
  if (lineIndexB>points_list.data.length-1) return;
    
  setTimeout(function() {
    											drawLines()
                				}, 1000);
}

drawLines();

＆＃13;

<canvas id="canvas"></canvas>

＆＃13;

画布动画画线

1 个答案: