Chart.js - 多折线图 - 仅显示最后一个图表

我正在使用 Chart.js 在一页上显示多个折线图。然而，尽管我将它们称为#canvas1 和#canvas2，但只有最后一张图表显示。某处一定有什么冲突，我已经尝试了大多数事情，但没有任何快乐。这是两张图表，仅显示最后一张：

图一

<script type="text/javascript">

    var lineChartData = {
        labels : ["January","February","March","April","May","June","July","August","September","October","November","December"],
        datasets : [
            {
                label: "Target",
                fillColor : "rgba(220,220,220,0.2)",
                strokeColor : "rgba(220,220,220,1)",
                pointColor : "rgba(220,220,220,1)",
                pointStrokeColor : "#fff",
                pointHighlightFill : "#fff",
                pointHighlightStroke : "rgba(220,220,220,1)",
                data : [160000,175000,185000,180000,185000,185000,185000,195000,200000,0,0]
            },
            {
                label: "Sales",
                fillColor : "rgba(151,187,205,0.2)",
                strokeColor : "rgba(151,187,205,1)",
                pointColor : "rgba(151,187,205,1)",
                pointStrokeColor : "#fff",
                pointHighlightFill : "#fff",
                pointHighlightStroke : "rgba(151,187,205,1)",
                data : [<?php echo $stockJanuary ?>,<?php echo $stockFebruary ?>,<?php echo $stockMarch ?>,<?php echo $stockApril ?>,<?php echo $stockMay ?>,<?php echo $stockJune ?>,<?php echo $stockJuly ?>,<?php echo $stockAugust ?>,<?php echo $stockSeptember ?>,<?php echo $stockOctober ?>,<?php echo $stockNovember ?>,<?php echo $stockDecember ?>]
            }
        ]

    }
            window.onload = function(){
    var ctx = document.getElementById("canvas1").getContext("2d");
    window.myLine = new Chart(ctx).Line(lineChartData, {
        responsive: true
    });
}
</script>

图二：

<script type="text/javascript">

    var lineChartData = {
        labels : ["January","February","March","April","May","June","July","August","September","October","November","December"],
        datasets : [
            {
                label: "Target",
                fillColor : "rgba(220,220,220,0.2)",
                strokeColor : "rgba(220,220,220,1)",
                pointColor : "rgba(220,220,220,1)",
                pointStrokeColor : "#fff",
                pointHighlightFill : "#fff",
                pointHighlightStroke : "rgba(220,220,220,1)",
                data : [19000,21000,23000,25000,27000,29000,31000,32000,33000,0,0]
            },
            {
                label: "Sales",
                fillColor : "rgba(151,187,205,0.2)",
                strokeColor : "rgba(151,187,205,1)",
                pointColor : "rgba(151,187,205,1)",
                pointStrokeColor : "#fff",
                pointHighlightFill : "#fff",
                pointHighlightStroke : "rgba(151,187,205,1)",
                data : [<?php echo $northJanuary ?>,<?php echo $northFebruary ?>,<?php echo $northMarch ?>,<?php echo $northApril ?>,<?php echo $northMay ?>,<?php echo $northJune ?>,<?php echo $northJuly ?>,<?php echo $northAugust ?>,<?php echo $northSeptember ?>,<?php echo $northOctober ?>,<?php echo $northNovember ?>,<?php echo $northDecember ?>]
            }
        ]

    }

    window.onload = function(){
    var ctx = document.getElementById("canvas2").getContext("2d");
    window.myLine = new Chart(ctx).Line(lineChartData, {
    responsive: true
    });



}

</script>

非常感谢您的帮助，已经困扰我一段时间了！

提前致谢

尝试对两个 ctx 变量使用不同的名称。

window.onload = function(){
    var ctx = document.getElementById("canvas2").getContext("2d");
    window.myLine = new Chart(ctx).Line(lineChartData, {
        responsive: true
    });


    var ctx2 = document.getElementById("canvas1").getContext("2d");
    window.myLine = new Chart(ctx2).Line(lineChartData2, {
        responsive: true
    });   
}