[英]Chart.JS: How can I only display data labels when the doughnut size is big enough for the text?
[英]Chart.JS: How can I only display data labels when the bar width is big enough for the text?
我正在将Chart.JS与Chart.JS datalabel插件一起使用 。 条形图的宽度足以容纳文本时,是否只能显示数据标签?
我有以下示例:
https://jsfiddle.net/f5p3twcg/2/
var ctx = document.getElementById("myChart");
var myChart = new Chart(ctx, {
plugins: [ChartDataLabels],
type: 'bar',
options: {
plugins: {
datalabels: {
color: '#000000',
display: true,
formatter: function(value, ctx) {
return value + "kWh";
}
}
}
},
data: {
labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange", "Red1", "Blue1", "Yellow1", "Green1", "Purple1", "Orange1", "Red2", "Blue2", "Yellow2", "Green2", "Purple2", "Orange2", "Red3", "Blue3", "Yellow3", "Green3", "Purple3", "Orange3", "Red4", "Blue4", "Yellow4", "Green4", "Purple4", "Orange4"],
datasets: [{
label: '# of Votes',
data: [12, 19, 3, 5, 2, 3, 12, 19, 3, 5, 2, 3, 12, 19, 3, 5, 2, 3, 12, 19, 3, 5, 2, 3, 12, 19, 3, 5, 2, 3, 12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
]
}]
}
});
我知道,这个示例没有任何意义,但是您可以看到问题所在。
如果有大量数据,数据标签将像这样溢出条形宽度:
是否可以告诉Chart.JS仅在文本适合条形时才显示这些标签? (否则,请显示工具提示)。
如果图形没有动态更改大小,则可以使用以下命令创建图表实例后获得条形图的宽度
var width = myChart.getDatasetMeta(0).data[0]._model.width;
并重写您的格式化程序,以检查文本宽度是否不超过栏的宽度
formatter: function (value, ctx) {
function getTextWidth(text, font) {
// re-use canvas object for better performance
var canvas = getTextWidth.canvas || (getTextWidth.canvas = document.createElement("canvas"));
var context = canvas.getContext("2d");
context.font = font;
var metrics = context.measureText(text);
return metrics.width;
}
return getTextWidth(value + "kWh") > width ? "" : value + "kWh";
}
请注意我之前在示例中忽略了字体,因此,如果进行了任何更改,则必须手动提取它。
您甚至可以编写一个插件,在渲染之前将其写入var width
变量
plugins: [
ChartDataLabels,
{
beforeRender: (myChart) => { width = myChart.getDatasetMeta(0).data[1]._model.width;}
}
],
Krzysztof Krzeszewski的解决方案起作用。 但是,在我的情况下,我必须对其稍加调整并添加一些针对'undefined'
检查:
if (typeof chart !== 'undefined') {
let datasetData = chart.getDatasetMeta(0);
if (datasetData !== 'undefined') {
if (datasetData.data.length > 0) {
barWidth = chart.getDatasetMeta(0).data[0]._model.width;
}
}
}
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