前言
- 小程序学习和应用已经两月有余，一直没有时间去整理所学的东西，实在是惭愧。
- 从IOS到小程序，给我最大的感受就是，这些大厂（苹果or腾讯）对其生态圈的开发者的管制简直比处女都紧
- 由于生产需要，自己实现了一个canvas绘制线性图表的demo。
开始
- 为了更多样的UI效果，接口暴露了较多的参数，以下是所有暴露的参数，都有详细说明，就不再赘述
/**
* options
*
* context 绘制上下文 require
* xNumArray 横轴数据 require
* yNumArray 纵轴数据 require
* xArray 横轴展示数据 default xNumArray
* yArray 纵轴展示数据 default yNumArray
* widht 宽度 default 200xp
* height 高度 default 200xp
* isShowX 是否展示横轴数据 默认展示（ture）
* isShowY 是否展示纵轴数据 默认展示（ture）
* isShowAxisX 是否展示横轴 默认展示（ture）
* isShowAxisY 是否展示纵轴 默认展示（ture）
* isYRight 纵轴是否在右边，默认在左边（false）
* xAxisColor x轴的颜色 default #000000
* yAxisColor y轴的颜色 default #000000
* pathColor 绘制线的颜色 default #000000
* gradientStartColor 背景渐变色开始 default #1CB0F6
* gradientEndColor 背景渐变色结束 default #ffffff
* paddingLeft 左边距 default 20
* paddingRight 右边距 default 20
* fixedY y轴数据保留小数点位数，default 2
*/
- 参数初始化
// 参数初始化
if (!options || Object.keys(options).length == 0) {
console.warn('请初始化options')
return
}
let context = options.context
if (!context) {
console.warn('请初始化context')
return
}
let xNumArray = options.xNumArray
if (!xNumArray || xNumArray.length == 0) {
console.warn('请初始化xNumArray')
return
}
let yNumArray = options.yNumArray
if (!yNumArray || yNumArray.length == 0) {
console.warn('请初始化yNumArray')
return
}
let xArray = options.xArray || xNumArray
let yArray = options.yArray || yNumArray
let width = options.width || 200
let height = options.height || 200
let gradientStartColor = options.gradientStartColor || 'rgba(28,176,246,0.6)'
let gradientEndColor = options.gradientStartColor || '#ffffff'
let isShowX = options.isShowX
let isShowY = options.isShowY
let isYRight = options.isYRight
let isShowAxisX = options.isShowAxisX
let isShowAxisY = options.isShowAxisY
let paddingLeft = options.paddingLeft
let paddingRight = options.paddingRight
let fixedY = options.fixedY
if (isShowX == undefined) {
isShowX = true
}
if (isShowY == undefined) {
isShowY = true
}
if (isShowAxisX == undefined) {
isShowAxisX = true
}
if (isShowAxisY == undefined) {
isShowAxisY = true
}
if (isYRight == undefined) {
isYRight = false
}
if (paddingLeft == undefined) {
paddingLeft = 20
}
if (paddingRight == undefined) {
paddingRight = 20
}
if (fixedY == undefined) {
fixedY = 2
}
let xAxisColor = options.xAxisColor || '#000000'
let yAxisColor = options.yAxisColor || '#000000'
let pathColor = options.pathColor || '#000000'
let xCount = xNumArray.length
let yCount = yNumArray.length
if (xCount > yCount) {
console.warn('横轴元素长度小于或者等于纵轴元素长度')
return
} else if (xCount < yCount) {
xNumArray = []
for (let index = 0; index < yNumArray.length; index++) {
xNumArray.push(index)
}
}
// 数据都转化为number类型
for (let index = 0; index < yNumArray.length; index++) {
yNumArray[index] = parseFloat(yNumArray[index])
}
- 绘制前准备工作
// 给y轴数据排序 bubbleSort为排序方法
let sortYArray = bubbleSort(yArray)
let sortYNumArray = bubbleSort(yNumArray)
let minY = sortYNumArray[0]
let maxY = sortYNumArray[sortYNumArray.length - 1]
- 绘制横纵坐标
// 绘制
let margin = 20 // 上下边距
// 绘制横纵坐标
let x = paddingLeft
let y = margin
if (isShowAxisY) {
context.setStrokeStyle(yAxisColor)
// y轴在右边
if (isYRight) {
x = width - paddingRight
}
context.beginPath()
context.moveTo(x, y)
context.lineTo(x, height - margin)
context.closePath()
context.stroke()
}
// x轴
if (isShowAxisX) {
context.setStrokeStyle(xAxisColor)
x = paddingLeft
y = height - margin
context.beginPath()
context.moveTo(x, y)
context.lineTo(width - paddingRight, y)
context.closePath()
context.stroke()
}
- 绘制数据线
// 绘制数据线
let canvesAreaW = width - (paddingLeft + paddingRight)
let canvesAreaH = height - (2 * margin)
context.beginPath()
context.moveTo(paddingLeft, height - margin)
context.lineTo(x, y)
context.setStrokeStyle(pathColor)
for (let index = 0; index < xNumArray.length; index++) {
let yElement = yNumArray[index]
x = paddingLeft + ((canvesAreaW / (xNumArray.length - 1)) * (index))
let skip = maxY - minY
if (skip == 0) {
y = margin
} else {
y = height - margin - (canvesAreaH / (maxY - minY) * (yElement - minY))
}
context.lineTo(x, y)
}
- 填充颜色，（这里可以根据需要省略）
context.lineTo(width - paddingRight, height - margin)
context.setStrokeStyle(pathColor)
context.stroke();
var my_gradient = context.createLinearGradient(0, 0, 0, height - margin);
my_gradient.addColorStop(0, gradientStartColor); //定义黄色渐变色
my_gradient.addColorStop(1, gradientEndColor); //定义红色渐变色
context.setFillStyle(my_gradient)
context.fill()
- 绘制数字下标
// 数字下边添加
// x 轴
context.setTextAlign('center')
context.setFillStyle(xAxisColor)
context.setFontSize(12)
// context.fillText(0, margin, height - 8)
if (isShowX) {
for (let index = 0; index < xArray.length; index++) {
const element = xArray[index];
y = height - 8
x = (canvesAreaW / (xArray.length - 1)) * (index) + paddingLeft
context.fillText(element, x, y)
}
}
// y轴
if (isShowY) {
for (let index = 0; index < sortYArray.length; index++) {
x = 20
if (isYRight) {
x = width - (paddingRight / 2)
}
if ((maxY - minY) == 0) {
y = margin
} else {
y = height - (canvesAreaH / (yArray.length - 1)) * (index) - margin
}
context.fillText((sortYArray[index]).toFixed(fixedY), x, y)
}
}
- 绘制
context.draw()
调用
- js文件
// 引入
import bsCharts from './bs-charts.js'
onLoad: function (options) {
let ctx = wx.createCanvasContext('canvasQr', this)
let xNumArray = [1, 2, 3, 4, 5, 6]
let yNumArray = [23, 4, 55, 64, 6,10]
bsCharts({
context: ctx,
xNumArray: xNumArray,
yNumArray: yNumArray,
isYRight:true,
paddingRight:40,
// 其他参数可以按需设置
})
},
- wxml文件
<canvas canvas-id = 'canvasQr' style = 'width:200px ; height:200px'></canvas>
样式
image.png
最后
其实很简单，也没必要过多叙述，目的就是记录一下自己最近所学
