Android自定義折線圖控制元件的完整步驟

2022-06-06 22:03:15

前言

日前，有一個“折現圖”的需求，如下圖所示：

概述

如何自定義折線圖？首先將折線圖的繪製部分拆分成三部分：

原點
X軸
Y軸
折線

原點

第一步，需要定義出“折線圖”原點的位置，由圖得：

可以發現，原點的位置由X軸、Y軸所佔空間決定：

OriginX：Y軸寬度
OriginY：View高度 - X軸高度

計算Y軸寬度

思路：遍歷Y軸的繪製文字，用畫筆測量其最大寬度，在加上其左右Margin間距即Y軸寬度

Y軸寬度 = Y軸MarginLeft + Y軸最大文字寬度 + Y軸MariginRight

計算X軸高度

思路：獲取X軸畫筆FontMetrics，根據其top、bottom計算出X軸文字高度，在加上其上下Margin間距即X軸高度

val fontMetrics = xAxisTextPaint.fontMetrics
val lineHeight = fontMetrics.bottom - fontMetrics.top
xAxisHeight = lineHeight + xAxisOptions.textMarginTop + xAxisOptions.textMarginBottom

X軸

第二步，根據原點位置，繪製X軸軸線、格線、文字

繪製軸線

繪製軸線比較簡單，沿原點向控制元件右側畫一條直線即可

if (xAxisOptions.isEnableLine) {
    xAxisLinePaint.strokeWidth = xAxisOptions.lineWidth
    xAxisLinePaint.color = xAxisOptions.lineColor
    xAxisLinePaint.pathEffect = xAxisOptions.linePathEffect
    canvas.drawLine(originX, originY, width.toFloat(), originY, xAxisLinePaint)
}

X軸刻度間隔

在繪製格線、文字之前需要先計算X軸的刻度間隔：

這裡處理的方式比較隨意，直接將X軸等分7份即可（因為需要顯示近7天的資料）

xGap = (width - originX) / 7

格線、文字

格線：只需要根據X軸的刻度，沿Y軸方向依次向控制元件頂部，畫直線即可

文字：文字需要通過畫筆，提前測量出待繪製文字的區域，然後計算出居中位置繪製即可

xAxisTexts.forEachIndexed { index, text ->
    val pointX = originX + index * xGap
    //刻度線
    if (xAxisOptions.isEnableRuler) {
        xAxisLinePaint.strokeWidth = xAxisOptions.rulerWidth
        xAxisLinePaint.color = xAxisOptions.rulerColor
        canvas.drawLine(
            pointX, originY,
            pointX, originY - xAxisOptions.rulerHeight,
            xAxisLinePaint
        )
    }
    //格線
    if (xAxisOptions.isEnableGrid) {
        xAxisLinePaint.strokeWidth = xAxisOptions.gridWidth
        xAxisLinePaint.color = xAxisOptions.gridColor
        xAxisLinePaint.pathEffect = xAxisOptions.gridPathEffect
        canvas.drawLine(pointX, originY, pointX, 0f, xAxisLinePaint)
    }
    //文字
    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軸

第三步：根據原點位置，繪製Y軸軸線、格線、文字

計算Y軸分佈

個人認為，這裡是自定義折線圖的一個難點，這裡經過查閱資料，使用該文章中的演演算法：

基於魔數陣列的座標軸刻度取值演演算法

/**
 * 根據Y軸最大值、數量獲取Y軸的標準間隔
 */
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()
}

/**
 * 根據初始的歸一化後的間隔,轉化為目標的間隔
 */
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
    }
}

刻度間隔、格線、文字

Y軸的軸線、格線、文字剩下的內容與X軸的處理方式幾乎一致

//繪製Y軸
//軸線
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 ->
    //刻度線
    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
        )
    }
    //格線
    if (yAxisOptions.isEnableGrid) {
        yAxisLinePaint.strokeWidth = yAxisOptions.gridWidth
        yAxisLinePaint.color = yAxisOptions.gridColor
        yAxisLinePaint.pathEffect = yAxisOptions.gridPathEffect
        canvas.drawLine(originX, pointY, width.toFloat(), pointY, yAxisLinePaint)
    }
    //文字
    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)
}

折線

折線的連線，這裡使用的是Path，將一個一個座標點連線，最後將Path繪製，就形成了圖中的折線圖

//繪製資料
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)
    }
    //圓點
    circlePaint.color = dataOptions.circleColor
    canvas.drawCircle(x, y, dataOptions.circleRadius, circlePaint)
}
pathPaint.strokeWidth = dataOptions.pathWidth
pathPaint.color = dataOptions.pathColor
canvas.drawPath(path, pathPaint)

值得注意的是：座標點X根據間隔是相對確定的，而座標點Y則需要進行百分比換算

程式碼

折線圖LineChart

package com.vander.pool.widget.linechart
import android.content.Context
import android.graphics.*
import android.text.TextPaint
import android.util.AttributeSet
import android.view.View
import java.text.DecimalFormat
import kotlin.math.floor
import kotlin.math.log10
import kotlin.math.pow
import kotlin.math.roundToInt
class LineChart : View {
    private var options = ChartOptions()
    /**
     * X軸相關
     */
    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
    /**
     * Y軸相關
     */
    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
    /**
     * 原點
     */
    private var originX = 0f
    private var originY = 0f
    private var xGap = 0f
    private var yGap = 0f
    /**
     * 資料相關
     */
    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
        //設定原點
        originX = yAxisWidth
        originY = height - xAxisHeight
        //設定X軸Y軸間隔
        xGap = (width - originX) / points.size
        //Y軸預設頂部會留出一半空間
        yGap = originY / (yAxisCount - 1 + 0.5f)
        //繪製X軸
        //軸線
        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
            //刻度線
            if (xAxisOptions.isEnableRuler) {
                xAxisLinePaint.strokeWidth = xAxisOptions.rulerWidth
                xAxisLinePaint.color = xAxisOptions.rulerColor
                canvas.drawLine(
                    pointX, originY,
                    pointX, originY - xAxisOptions.rulerHeight,
                    xAxisLinePaint
                )
            }
            //格線
            if (xAxisOptions.isEnableGrid) {
                xAxisLinePaint.strokeWidth = xAxisOptions.gridWidth
                xAxisLinePaint.color = xAxisOptions.gridColor
                xAxisLinePaint.pathEffect = xAxisOptions.gridPathEffect
                canvas.drawLine(pointX, originY, pointX, 0f, xAxisLinePaint)
            }
            //文字
            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)
        }
        //繪製Y軸
        //軸線
        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 ->
            //刻度線
            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
                )
            }
            //格線
            if (yAxisOptions.isEnableGrid) {
                yAxisLinePaint.strokeWidth = yAxisOptions.gridWidth
                yAxisLinePaint.color = yAxisOptions.gridColor
                yAxisLinePaint.pathEffect = yAxisOptions.gridPathEffect
                canvas.drawLine(originX, pointY, width.toFloat(), pointY, yAxisLinePaint)
            }
            //文字
            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)
        }
        //繪製資料
        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)
            }
            //圓點
            circlePaint.color = dataOptions.circleColor
            canvas.drawCircle(x, y, dataOptions.circleRadius, circlePaint)
        }
        pathPaint.strokeWidth = dataOptions.pathWidth
        pathPaint.color = dataOptions.pathColor
        canvas.drawPath(path, pathPaint)
    }
    /**
     * 設定資料
     */
    fun setData(list: List<ChartBean>) {
        points.clear()
        points.addAll(list)
        //設定X軸、Y軸資料
        setXAxisData(list)
        setYAxisData(list)
        invalidate()
    }
    /**
     * 設定X軸資料
     */
    private fun setXAxisData(list: List<ChartBean>) {
        val xAxisOptions = options.xAxisOptions
        val values = list.map { it.xAxis }
        //X軸文字
        xAxisTexts.clear()
        xAxisTexts.addAll(values)
        //X軸高度
        val fontMetrics = xAxisTextPaint.fontMetrics
        val lineHeight = fontMetrics.bottom - fontMetrics.top
        xAxisHeight = lineHeight + xAxisOptions.textMarginTop + xAxisOptions.textMarginBottom
    }
    /**
     * 設定Y軸資料
     */
    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軸高度
        val maxTextWidth = yAxisTexts.maxOf { yAxisTextPaint.measureText(it) }
        yAxisWidth = maxTextWidth + yAxisOptions.textMarginLeft + yAxisOptions.textMarginRight
        //Y軸間隔
        val maxY = list.maxOf { it.yAxis }
        val interval = when {
            maxY <= 10 -> getYInterval(10)
            else -> getYInterval(maxY)
        }
        //Y軸文字
        yAxisTexts.clear()
        for (index in 0..yAxisCount) {
            val value = index * interval
            yAxisTexts.add(formatNum(value))
        }
        yAxisMaxValue = (yAxisCount - 1) * interval
    }
    /**
     * 格式化數值
     */
    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"
        }
    }
    /**
     * 根據Y軸最大值、數量獲取Y軸的標準間隔
     */
    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()
    }
    /**
     * 根據初始的歸一化後的間隔,轉化為目標的間隔
     */
    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
        }
    }
    /**
     * 重置引數
     */
    fun setOptions(newOptions: ChartOptions) {
        this.options = newOptions
        setData(points)
    }
    fun getOptions(): ChartOptions {
        return options
    }
    data class ChartBean(val xAxis: String, val yAxis: Int)
}

ChartOptions設定選項

class ChartOptions {
    //X軸設定
    var xAxisOptions = AxisOptions()
    //Y軸設定
    var yAxisOptions = AxisOptions()
    //資料設定
    var dataOptions = DataOptions()
}
/**
 * 軸線設定引數
 */
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
    }
    /**
     * 文字大小
     */
    @FloatRange(from = 1.0)
    var textSize: Float = DEFAULT_TEXT_SIZE
    @ColorInt
    var textColor: Int = DEFAULT_TEXT_COLOR
    /**
     * X軸文字內容上下兩側margin
     */
    var textMarginTop: Int = DEFAULT_TEXT_MARGIN
    var textMarginBottom: Int = DEFAULT_TEXT_MARGIN
    /**
     * Y軸文字內容左右兩側margin
     */
    var textMarginLeft: Int = DEFAULT_TEXT_MARGIN
    var textMarginRight: Int = DEFAULT_TEXT_MARGIN
    /**
     * 軸線
     */
    var lineWidth: Float = DEFAULT_LINE_WIDTH
    @ColorInt
    var lineColor: Int = DEFAULT_TEXT_COLOR
    var isEnableLine = true
    var linePathEffect: PathEffect? = null
    /**
     * 刻度
     */
    var rulerWidth = DEFAULT_LINE_WIDTH
    var rulerHeight = DEFAULT_RULER_WIDTH
    @ColorInt
    var rulerColor = DEFAULT_TEXT_COLOR
    var isEnableRuler = true
    /**
     * 網格
     */
    var gridWidth: Float = DEFAULT_LINE_WIDTH
    @ColorInt
    var gridColor: Int = DEFAULT_TEXT_COLOR
    var gridPathEffect: PathEffect? = null
    var isEnableGrid = true
}
/**
 * 資料設定引數
 */
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樣式

private fun initView() {
    val options = binding.chart.getOptions()
    //X軸
    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軸
    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
    //資料
    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&lt;LineChart.ChartBean&gt;()
    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)
    //文字
    val text = list.joinToString("n") {
        "x : ${it.xAxis}  y:${it.yAxis}"
    }
    binding.value.text = text
}