这篇“Android怎么实现自定义折线图控件”文章的知识点大部分人都不太理解，所以小编给大家总结了以下内容，内容详细，步骤清晰，具有一定的借鉴价值，希望大家阅读完这篇文章能有所收获，下面我们一起来看看这篇“Android怎么实现自定义折线图控件”文章吧。
前言
日前，有一个“折现图”的需求，如下图所示：
概述
如何自定义折线图？首先将折线图的绘制部分拆分成三部分：
原点
X轴
Y轴
折线
原点
第一步，需要定义出“折线图”原点的位置，由图得：
可以发现，原点的位置由X轴、Y轴所占空间决定：
OriginX：Y轴宽度OriginY：View高度 - X轴高度计算Y轴宽度
思路：遍历Y轴的绘制文字，用画笔测量其最大宽度，在加上其左右Margin间距即Y轴宽度
Y轴宽度 = Y轴MarginLeft + Y轴最大文字宽度 + Y轴MariginRight
计算X轴高度
思路：获取X轴画笔FontMetrics，根据其top、bottom计算出X轴文字高度，在加上其上下Margin间距即X轴高度
val fontMetrics = xAxisTextPaint.fontMetricsval lineHeight = fontMetrics.bottom - fontMetrics.topxAxisHeight = lineHeight + xAxisOptions.textMarginTop + xAxisOptions.textMarginBottomX轴
第二步，根据原点位置，绘制X轴轴线、网格线、文本
绘制轴线
绘制轴线比较简单，沿原点向控件右侧画一条直线即可
if (xAxisOptions.isEnableLine) { xAxisLinePaint.strokeWidth = xAxisOptions.lineWidth xAxisLinePaint.color = xAxisOptions.lineColor xAxisLinePaint.pathEffect = xAxisOptions.linePathEffect canvas.drawLine(originX, originY, width.toFloat(), originY, xAxisLinePaint)}X轴刻度间隔
在绘制网格线、文本之前需要先计算X轴的刻度间隔：
这里处理的方式比较随意，直接将X轴等分7份即可（因为需要显示近7天的数据）
xGap = (width - originX) / 7网格线、文本
网格线：只需要根据X轴的刻度，沿Y轴方向依次向控件顶部，画直线即可
文本：文本需要通过画笔，提前测量出待绘制文本的区域，然后计算出居中位置绘制即可
xAxisTexts.forEachIndexed { index, text -> val pointX = originX + index * xGap //刻度线 if (xAxisOptions.isEnableRuler) { xAxisLinePaint.strokeWidth = xAxisOptions.rulerWidth xAxisLinePaint.color = xAxisOptions.rulerColor canvas.drawLine( pointX, originY, pointX, originY - xAxisOptions.rulerHeight, xAxisLinePaint ) } //网格线 if (xAxisOptions.isEnableGrid) { xAxisLinePaint.strokeWidth = xAxisOptions.gridWidth xAxisLinePaint.color = xAxisOptions.gridColor xAxisLinePaint.pathEffect = xAxisOptions.gridPathEffect canvas.drawLine(pointX, originY, pointX, 0f, xAxisLinePaint) } //文本 bounds.setEmpty() xAxisTextPaint.textSize = xAxisOptions.textSize xAxisTextPaint.color = xAxisOptions.textColor xAxisTextPaint.getTextBounds(text, 0, text.length, bounds) val fm = xAxisTextPaint.fontMetrics val fontHeight = fm.bottom - fm.top val fontX = originX + index * xGap + (xGap - bounds.width()) / 2f val fontBaseline = originY + (xAxisHeight - fontHeight) / 2f - fm.top canvas.drawText(text, fontX, fontBaseline, xAxisTextPaint)}Y轴
第三步：根据原点位置，绘制Y轴轴线、网格线、文本
计算Y轴分布
个人认为，这里是自定义折线图的一个难点，这里经过查阅资料，使用该文章中的算法：
基于JavaScript实现数值型坐标轴刻度计算算法(echarts的y轴刻度计算)
private fun getYInterval(maxY: Int): Int { val yIntervalCount = yAxisCount - 1 val rawInterval = maxY / yIntervalCount.toFloat() val magicPower = floor(log10(rawInterval.toDouble())) var magic = 10.0.pow(magicPower).toFloat() if (magic == rawInterval) { magic = rawInterval } else { magic *= 10 } val rawStandardInterval = rawInterval / magic val standardInterval = getStandardInterval(rawStandardInterval) * magic return standardInterval.roundToInt()}private fun getStandardInterval(x: Float): Float { return when { x <= 0.1f -> 0.1f x <= 0.2f -> 0.2f x <= 0.25f -> 0.25f x <= 0.5f -> 0.5f x <= 1f -> 1f else -> getStandardInterval(x / 10) * 10 }}刻度间隔、网格线、文本
Y轴的轴线、网格线、文本剩下的内容与X轴的处理方式几乎一致
//绘制Y轴//轴线if (yAxisOptions.isEnableLine) { yAxisLinePaint.strokeWidth = yAxisOptions.lineWidth yAxisLinePaint.color = yAxisOptions.lineColor yAxisLinePaint.pathEffect = yAxisOptions.linePathEffect canvas.drawLine(originX, 0f, originX, originY, yAxisLinePaint)}yAxisTexts.forEachIndexed { index, text -> //刻度线 val pointY = originY - index * yGap if (yAxisOptions.isEnableRuler) { yAxisLinePaint.strokeWidth = yAxisOptions.rulerWidth yAxisLinePaint.color = yAxisOptions.rulerColor canvas.drawLine( originX, pointY, originX + yAxisOptions.rulerHeight, pointY, yAxisLinePaint ) } //网格线 if (yAxisOptions.isEnableGrid) { yAxisLinePaint.strokeWidth = yAxisOptions.gridWidth yAxisLinePaint.color = yAxisOptions.gridColor yAxisLinePaint.pathEffect = yAxisOptions.gridPathEffect canvas.drawLine(originX, pointY, width.toFloat(), pointY, yAxisLinePaint) } //文本 bounds.setEmpty() yAxisTextPaint.textSize = yAxisOptions.textSize yAxisTextPaint.color = yAxisOptions.textColor yAxisTextPaint.getTextBounds(text, 0, text.length, bounds) val fm = yAxisTextPaint.fontMetrics val x = (yAxisWidth - bounds.width()) / 2f val fontHeight = fm.bottom - fm.top val y = originY - index * yGap - fontHeight / 2f - fm.top canvas.drawText(text, x, y, yAxisTextPaint)}折线
折线的连接，这里使用的是Path，将一个一个坐标点连接，最后将Path绘制，就形成了图中的折线图
//绘制数据path.reset()points.forEachIndexed { index, point -> val x = originX + index * xGap + xGap / 2f val y = originY - (point.yAxis.toFloat() / yAxisMaxValue) * (yGap * (yAxisCount - 1)) if (index == 0) { path.moveTo(x, y) } else { path.lineTo(x, y) } //圆点 circlePaint.color = dataOptions.circleColor canvas.drawCircle(x, y, dataOptions.circleRadius, circlePaint)}pathPaint.strokeWidth = dataOptions.pathWidthpathPaint.color = dataOptions.pathColorcanvas.drawPath(path, pathPaint)值得注意的是：坐标点X根据间隔是相对确定的，而坐标点Y则需要进行百分比换算
代码
折线图LineChart
package com.vander.pool.widget.linechartimport android.content.Contextimport android.graphics.*import android.text.TextPaintimport android.util.AttributeSetimport android.view.Viewimport java.text.DecimalFormatimport kotlin.math.floorimport kotlin.math.log10import kotlin.math.powimport kotlin.math.roundToIntclass LineChart : View { private var options = ChartOptions() private val xAxisTextPaint = TextPaint(Paint.ANTI_ALIAS_FLAG) private val xAxisLinePaint = Paint(Paint.ANTI_ALIAS_FLAG) private val xAxisTexts = mutableListOf<String>() private var xAxisHeight = 0f private val yAxisTextPaint = TextPaint(Paint.ANTI_ALIAS_FLAG) private val yAxisLinePaint = Paint(Paint.ANTI_ALIAS_FLAG) private val yAxisTexts = mutableListOf<String>() private var yAxisWidth = 0f private val yAxisCount = 5 private var yAxisMaxValue: Int = 0 private var originX = 0f private var originY = 0f private var xGap = 0f private var yGap = 0f private val pathPaint = Paint(Paint.ANTI_ALIAS_FLAG).also { it.style = Paint.Style.STROKE } private val circlePaint = Paint(Paint.ANTI_ALIAS_FLAG).also { it.color = Color.parseColor("#79EBCF") it.style = Paint.Style.FILL } private val points = mutableListOf<ChartBean>() private val bounds = Rect() private val path = Path() constructor(context: Context) : this(context, null) constructor(context: Context, attrs: AttributeSet?) : this(context, attrs, 0) constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr) override fun onDraw(canvas: Canvas) { super.onDraw(canvas) if (points.isEmpty()) return val xAxisOptions = options.xAxisOptions val yAxisOptions = options.yAxisOptions val dataOptions = options.dataOptions //设置原点 originX = yAxisWidth originY = height - xAxisHeight //设置X轴Y轴间隔 xGap = (width - originX) / points.size //Y轴默认顶部会留出一半空间 yGap = originY / (yAxisCount - 1 + 0.5f) //绘制X轴 //轴线 if (xAxisOptions.isEnableLine) { xAxisLinePaint.strokeWidth = xAxisOptions.lineWidth xAxisLinePaint.color = xAxisOptions.lineColor xAxisLinePaint.pathEffect = xAxisOptions.linePathEffect canvas.drawLine(originX, originY, width.toFloat(), originY, xAxisLinePaint) } xAxisTexts.forEachIndexed { index, text -> val pointX = originX + index * xGap //刻度线 if (xAxisOptions.isEnableRuler) { xAxisLinePaint.strokeWidth = xAxisOptions.rulerWidth xAxisLinePaint.color = xAxisOptions.rulerColor canvas.drawLine( pointX, originY, pointX, originY - xAxisOptions.rulerHeight, xAxisLinePaint ) } //网格线 if (xAxisOptions.isEnableGrid) { xAxisLinePaint.strokeWidth = xAxisOptions.gridWidth xAxisLinePaint.color = xAxisOptions.gridColor xAxisLinePaint.pathEffect = xAxisOptions.gridPathEffect canvas.drawLine(pointX, originY, pointX, 0f, xAxisLinePaint) } //文本 bounds.setEmpty() xAxisTextPaint.textSize = xAxisOptions.textSize xAxisTextPaint.color = xAxisOptions.textColor xAxisTextPaint.getTextBounds(text, 0, text.length, bounds) val fm = xAxisTextPaint.fontMetrics val fontHeight = fm.bottom - fm.top val fontX = originX + index * xGap + (xGap - bounds.width()) / 2f val fontBaseline = originY + (xAxisHeight - fontHeight) / 2f - fm.top canvas.drawText(text, fontX, fontBaseline, xAxisTextPaint) } //绘制Y轴 //轴线 if (yAxisOptions.isEnableLine) { yAxisLinePaint.strokeWidth = yAxisOptions.lineWidth yAxisLinePaint.color = yAxisOptions.lineColor yAxisLinePaint.pathEffect = yAxisOptions.linePathEffect canvas.drawLine(originX, 0f, originX, originY, yAxisLinePaint) } yAxisTexts.forEachIndexed { index, text -> //刻度线 val pointY = originY - index * yGap if (yAxisOptions.isEnableRuler) { yAxisLinePaint.strokeWidth = yAxisOptions.rulerWidth yAxisLinePaint.color = yAxisOptions.rulerColor canvas.drawLine( originX, pointY, originX + yAxisOptions.rulerHeight, pointY, yAxisLinePaint ) } //网格线 if (yAxisOptions.isEnableGrid) { yAxisLinePaint.strokeWidth = yAxisOptions.gridWidth yAxisLinePaint.color = yAxisOptions.gridColor yAxisLinePaint.pathEffect = yAxisOptions.gridPathEffect canvas.drawLine(originX, pointY, width.toFloat(), pointY, yAxisLinePaint) } //文本 bounds.setEmpty() yAxisTextPaint.textSize = yAxisOptions.textSize yAxisTextPaint.color = yAxisOptions.textColor yAxisTextPaint.getTextBounds(text, 0, text.length, bounds) val fm = yAxisTextPaint.fontMetrics val x = (yAxisWidth - bounds.width()) / 2f val fontHeight = fm.bottom - fm.top val y = originY - index * yGap - fontHeight / 2f - fm.top canvas.drawText(text, x, y, yAxisTextPaint) } //绘制数据 path.reset() points.forEachIndexed { index, point -> val x = originX + index * xGap + xGap / 2f val y = originY - (point.yAxis.toFloat() / yAxisMaxValue) * (yGap * (yAxisCount - 1)) if (index == 0) { path.moveTo(x, y) } else { path.lineTo(x, y) } //圆点 circlePaint.color = dataOptions.circleColor canvas.drawCircle(x, y, dataOptions.circleRadius, circlePaint) } pathPaint.strokeWidth = dataOptions.pathWidth pathPaint.color = dataOptions.pathColor canvas.drawPath(path, pathPaint) } fun setData(list: List<ChartBean>) { points.clear() points.addAll(list) //设置X轴、Y轴数据 setXAxisData(list) setYAxisData(list) invalidate() } private fun setXAxisData(list: List<ChartBean>) { val xAxisOptions = options.xAxisOptions val values = list.map { it.xAxis } //X轴文本 xAxisTexts.clear() xAxisTexts.addAll(values) //X轴高度 val fontMetrics = xAxisTextPaint.fontMetrics val lineHeight = fontMetrics.bottom - fontMetrics.top xAxisHeight = lineHeight + xAxisOptions.textMarginTop + xAxisOptions.textMarginBottom } private fun setYAxisData(list: List<ChartBean>) { val yAxisOptions = options.yAxisOptions yAxisTextPaint.textSize = yAxisOptions.textSize yAxisTextPaint.color = yAxisOptions.textColor val texts = list.map { it.yAxis.toString() } yAxisTexts.clear() yAxisTexts.addAll(texts) //Y轴高度 val maxTextWidth = yAxisTexts.maxOf { yAxisTextPaint.measureText(it) } yAxisWidth = maxTextWidth + yAxisOptions.textMarginLeft + yAxisOptions.textMarginRight //Y轴间隔 val maxY = list.maxOf { it.yAxis } val interval = when { maxY <= 10 -> getYInterval(10) else -> getYInterval(maxY) } //Y轴文字 yAxisTexts.clear() for (index in 0..yAxisCount) { val value = index * interval yAxisTexts.add(formatNum(value)) } yAxisMaxValue = (yAxisCount - 1) * interval } private fun formatNum(num: Int): String { val absNum = Math.abs(num) return if (absNum >= 0 && absNum < 1000) { return num.toString() } else { val format = DecimalFormat("0.0") val value = num / 1000f "${format.format(value)}k" } } private fun getYInterval(maxY: Int): Int { val yIntervalCount = yAxisCount - 1 val rawInterval = maxY / yIntervalCount.toFloat() val magicPower = floor(log10(rawInterval.toDouble())) var magic = 10.0.pow(magicPower).toFloat() if (magic == rawInterval) { magic = rawInterval } else { magic *= 10 } val rawStandardInterval = rawInterval / magic val standardInterval = getStandardInterval(rawStandardInterval) * magic return standardInterval.roundToInt() } private fun getStandardInterval(x: Float): Float { return when { x <= 0.1f -> 0.1f x <= 0.2f -> 0.2f x <= 0.25f -> 0.25f x <= 0.5f -> 0.5f x <= 1f -> 1f else -> getStandardInterval(x / 10) * 10 } } fun setOptions(newOptions: ChartOptions) { this.options = newOptions setData(points) } fun getOptions(): ChartOptions { return options } data class ChartBean(val xAxis: String, val yAxis: Int)}ChartOptions配置选项：
class ChartOptions { //X轴配置 var xAxisOptions = AxisOptions() //Y轴配置 var yAxisOptions = AxisOptions() //数据配置 var dataOptions = DataOptions()}class AxisOptions { companion object { private const val DEFAULT_TEXT_SIZE = 20f private const val DEFAULT_TEXT_COLOR = Color.BLACK private const val DEFAULT_TEXT_MARGIN = 20 private const val DEFAULT_LINE_WIDTH = 2f private const val DEFAULT_RULER_WIDTH = 10f } @FloatRange(from = 1.0) var textSize: Float = DEFAULT_TEXT_SIZE @ColorInt var textColor: Int = DEFAULT_TEXT_COLOR var textMarginTop: Int = DEFAULT_TEXT_MARGIN var textMarginBottom: Int = DEFAULT_TEXT_MARGIN var textMarginLeft: Int = DEFAULT_TEXT_MARGIN var textMarginRight: Int = DEFAULT_TEXT_MARGIN var lineWidth: Float = DEFAULT_LINE_WIDTH @ColorInt var lineColor: Int = DEFAULT_TEXT_COLOR var isEnableLine = true var linePathEffect: PathEffect? = null var rulerWidth = DEFAULT_LINE_WIDTH var rulerHeight = DEFAULT_RULER_WIDTH @ColorInt var rulerColor = DEFAULT_TEXT_COLOR var isEnableRuler = true var gridWidth: Float = DEFAULT_LINE_WIDTH @ColorInt var gridColor: Int = DEFAULT_TEXT_COLOR var gridPathEffect: PathEffect? = null var isEnableGrid = true}class DataOptions { companion object { private const val DEFAULT_PATH_WIDTH = 2f private const val DEFAULT_PATH_COLOR = Color.BLACK private const val DEFAULT_CIRCLE_RADIUS = 10f private const val DEFAULT_CIRCLE_COLOR = Color.BLACK } var pathWidth = DEFAULT_PATH_WIDTH var pathColor = DEFAULT_PATH_COLOR var circleRadius = DEFAULT_CIRCLE_RADIUS var circleColor = DEFAULT_CIRCLE_COLOR}Demo样式：
private fun initView() { val options = binding.chart.getOptions() //X轴 val xAxisOptions = options.xAxisOptions xAxisOptions.isEnableLine = false xAxisOptions.textColor = Color.parseColor("#999999") xAxisOptions.textSize = dpToPx(12) xAxisOptions.textMarginTop = dpToPx(12).toInt() xAxisOptions.textMarginBottom = dpToPx(12).toInt() xAxisOptions.isEnableGrid = false xAxisOptions.isEnableRuler = false //Y轴 val yAxisOptions = options.yAxisOptions yAxisOptions.isEnableLine = false yAxisOptions.textColor = Color.parseColor("#999999") yAxisOptions.textSize = dpToPx(12) yAxisOptions.textMarginLeft = dpToPx(12).toInt() yAxisOptions.textMarginRight = dpToPx(12).toInt() yAxisOptions.gridColor = Color.parseColor("#999999") yAxisOptions.gridWidth = dpToPx(0.5f) val dashLength = dpToPx(8f) yAxisOptions.gridPathEffect = DashPathEffect(floatArrayOf(dashLength, dashLength / 2), 0f) yAxisOptions.isEnableRuler = false //数据 val dataOptions = options.dataOptions dataOptions.pathColor = Color.parseColor("#79EBCF") dataOptions.pathWidth = dpToPx(1f) dataOptions.circleColor = Color.parseColor("#79EBCF") dataOptions.circleRadius = dpToPx(3f) binding.chart.setOnClickListener { initChartData() } binding.toolbar.setLeftClick { finish() }}private fun initChartData() { val random = 1000 val list = mutableListOf<LineChart.ChartBean>() list.add(LineChart.ChartBean("05-01", Random.nextInt(random))) list.add(LineChart.ChartBean("05-02", Random.nextInt(random))) list.add(LineChart.ChartBean("05-03", Random.nextInt(random))) list.add(LineChart.ChartBean("05-04", Random.nextInt(random))) list.add(LineChart.ChartBean("05-05", Random.nextInt(random))) list.add(LineChart.ChartBean("05-06", Random.nextInt(random))) list.add(LineChart.ChartBean("05-07", Random.nextInt(random))) binding.chart.setData(list) //文本 val text = list.joinToString("\n") { "x : ${it.xAxis} y:${it.yAxis}" } binding.value.text = text}以上就是关于“Android怎么实现自定义折线图控件”这篇文章的内容，相信大家都有了一定的了解，希望小编分享的内容对大家有帮助，若想了解更多相关的知识内容，请关注编程网行业资讯频道。
