javascript – 在画布图中显示工具提示

2022-10-28 20:52:35

我使用html5 canvas元素绘制一个带有点的图形,表示here中的各个点.

我想在鼠标悬停的不同点上显示不同的工具提示.用户将提供要显示为工具提示的文本.

我尝试但无法弄清楚如何将图钉添加到图中的各个点.我用于显示点的代码是..

// Draw the dots
c.fillStyle = '#333';

for (var i = 0; i < data.values.length; i++) {
  c.beginPath();
  c.arc(getXPixel(data.values[i].X), getYPixel(data.values[i].Y), 4, 0, Math.PI * 2, true);
  c.fill();
}

我应该在此代码中添加什么,以便我能够将用户输入显示为工具提示？

解决方法:

当用户移动到图表的数据点时,您可以显示工具提示

此工具提示只是第二个画布,它从链接的文本框中绘制文本,并将其自身定位在数据点上方.

首先,您创建一个数组来保存每个数据点的工具提示信息.

    var dots = [];

对于每个工具提示,您将需要：

>数据点的x / y坐标,
>数据点的半径,
>您想要获取提示的文本框的ID.
>你还需要总是==半径平方的rXr(在命中测试期间需要)

以下是用于创建要存储在点[]中的工具提示信息的代码

    // define tooltips for each data point

    for(var i = 0; i < data.values.length; i ++) {
        dots.push({
            x: getXPixel(data.values[i].X),
            y: getYPixel(data.values[i].Y),
            r: 4,
            rXr: 16,
            tip: "#text"+(i+1)
        });
    }

然后设置一个通过点阵列查看的mousemove处理程序.如果用户在任何data = dot内移动,则会显示工具提示：

    // request mousemove events

    $("#graph").mousemove(function(e){handleMouseMove(e);});

    // show tooltip when mouse hovers over dot
    function handleMouseMove(e){
      mouseX=parseInt(e.clientX-offsetX);
      mouseY=parseInt(e.clientY-offsetY);

      // Put your mousemove stuff here
      var hit = false;
      for (var i = 0; i < dots.length; i++) {
          var dot = dots[i];
          var dx = mouseX - dot.x;
          var dy = mouseY - dot.y;
          if (dx * dx + dy * dy < dot.rXr) {
              tipCanvas.style.left = (dot.x) + "px";
              tipCanvas.style.top = (dot.y - 40) + "px";
              tipCtx.clearRect(0, 0, tipCanvas.width, tipCanvas.height);
              tipCtx.fillText($(dot.tip).val(), 5, 15);
              hit = true;
          }
      }
      if (!hit) { tipCanvas.style.left = "-200px"; }
    }

[已编辑以适合您的代码]

这是代码和小提琴：http://jsfiddle.net/m1erickson/yLBjM/

<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>

<style>
    body{ background-color: ivory; margin-top:35px; }
    #wrapper{position:relative; width:300px; height:150px;}
    canvas{border:1px solid red;}
    #tip{background-color:white; border:1px solid blue; position:absolute; left:-200px; top:100px;}
</style>

<script>
$(function(){

    var graph = document.getElementById("graph");
    var ctx = graph.getContext("2d");
    var tipCanvas = document.getElementById("tip");
    var tipCtx = tipCanvas.getContext("2d");

    var canvasOffset = $("#graph").offset();
    var offsetX = canvasOffset.left;
    var offsetY = canvasOffset.top;

    var graph;
    var xPadding = 30;
    var yPadding = 30;

    // Notice I changed The X values
    var data = { values:[
        { X: 0, Y: 12 },
        { X: 2, Y: 28 },
        { X: 3, Y: 18 },
        { X: 4, Y: 34 },
        { X: 5, Y: 40 },
        { X: 6, Y: 80 },
        { X: 7, Y: 80 }
    ]};

    // define tooltips for each data point
    var dots = [];
    for(var i = 0; i < data.values.length; i ++) {
        dots.push({
            x: getXPixel(data.values[i].X),
            y: getYPixel(data.values[i].Y),
            r: 4,
            rXr: 16,
            color: "red",
            tip: "#text"+(i+1)
        });
    }

    // request mousemove events
    $("#graph").mousemove(function(e){handleMouseMove(e);});

    // show tooltip when mouse hovers over dot
    function handleMouseMove(e){
      mouseX=parseInt(e.clientX-offsetX);
      mouseY=parseInt(e.clientY-offsetY);

      // Put your mousemove stuff here
      var hit = false;
      for (var i = 0; i < dots.length; i++) {
          var dot = dots[i];
          var dx = mouseX - dot.x;
          var dy = mouseY - dot.y;
          if (dx * dx + dy * dy < dot.rXr) {
              tipCanvas.style.left = (dot.x) + "px";
              tipCanvas.style.top = (dot.y - 40) + "px";
              tipCtx.clearRect(0, 0, tipCanvas.width, tipCanvas.height);
              tipCtx.fillText($(dot.tip).val(), 5, 15);
              hit = true;
          }
      }
      if (!hit) { tipCanvas.style.left = "-200px"; }
    }

//不变的代码如下

    // Returns the max Y value in our data list
    function getMaxY() {
        var max = 0;

        for(var i = 0; i < data.values.length; i ++) {
            if(data.values[i].Y > max) {
                max = data.values[i].Y;
            }
        }

        max += 10 - max % 10;
        return max;
    }

    // Returns the max X value in our data list
    function getMaxX() {
        var max = 0;

        for(var i = 0; i < data.values.length; i ++) {
            if(data.values[i].X > max) {
                max = data.values[i].X;
            }
        }

        // omited
      //max += 10 - max % 10;
        return max;
    }

    // Return the x pixel for a graph point
    function getXPixel(val) {
        // uses the getMaxX() function
        return ((graph.width - xPadding) / (getMaxX() + 1)) * val + (xPadding * 1.5);
        // was
      //return ((graph.width - xPadding) / getMaxX()) * val + (xPadding * 1.5);
    }

    // Return the y pixel for a graph point
    function getYPixel(val) {
        return graph.height - (((graph.height - yPadding) / getMaxY()) * val) - yPadding;
    }

        graph = document.getElementById("graph");
        var c = graph.getContext('2d');            

        c.lineWidth = 2;
        c.strokeStyle = '#333';
        c.font = 'italic 8pt sans-serif';
        c.textAlign = "center";

        // Draw the axises
        c.beginPath();
        c.moveTo(xPadding, 0);
        c.lineTo(xPadding, graph.height - yPadding);
        c.lineTo(graph.width, graph.height - yPadding);
        c.stroke();

        // Draw the X value texts
        var myMaxX = getMaxX();
        for(var i = 0; i <= myMaxX; i ++) {
            // uses data.values[i].X
            c.fillText(i, getXPixel(i), graph.height - yPadding + 20);
        }
        /* was
        for(var i = 0; i < data.values.length; i ++) {
            // uses data.values[i].X
            c.fillText(data.values[i].X, getXPixel(data.values[i].X), graph.height - yPadding + 20);
        }
        */

        // Draw the Y value texts
        c.textAlign = "right"
        c.textBaseline = "middle";

        for(var i = 0; i < getMaxY(); i += 10) {
            c.fillText(i, xPadding - 10, getYPixel(i));
        }

        c.strokeStyle = '#f00';

        // Draw the line graph
        c.beginPath();
        c.moveTo(getXPixel(data.values[0].X), getYPixel(data.values[0].Y));
        for(var i = 1; i < data.values.length; i ++) {
            c.lineTo(getXPixel(data.values[i].X), getYPixel(data.values[i].Y));
        }
        c.stroke();

        // Draw the dots
        c.fillStyle = '#333';

        for(var i = 0; i < data.values.length; i ++) {  
            c.beginPath();
            c.arc(getXPixel(data.values[i].X), getYPixel(data.values[i].Y), 4, 0, Math.PI * 2, true);
            c.fill();
        }


}); // end $(function(){});
</script>

</head>

<body>
    <div id="wrapper">
        <canvas id="graph" width=300 height=150></canvas>
        <canvas id="tip" width=100 height=25></canvas>
    </div>
    <br><br>
    <input type="text" id="text1" value="text 1"/><br><br>
    <input type="text" id="text2" value="text 2"/><br><br>
    <input type="text" id="text3" value="text 3"/><br><br>
    <input type="text" id="text4" value="text 4"/><br><br>
    <input type="text" id="text5" value="text 5"/><br><br>
    <input type="text" id="text6" value="text 6"/><br><br>
    <input type="text" id="text7" value="text 7"/><br><br>
</body>
</html>

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