自定义LoadingView kotlin实现

package com.example.mylibrary.view

import android.animation.ValueAnimator
import android.content.ContentValues
import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.util.AttributeSet
import android.util.Log
import android.view.View
import android.view.animation.LinearInterpolator
import com.example.mylibrary.log.LogUtils
import kotlin.math.max
import kotlin.math.sin


class LoadingView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : View(context, attrs, defStyleAttr) {

    var paint: Paint = Paint()

    private val count = 4

    var defaultSize = 200

    var lineHeight = 150f

    var defaultHeight = 150f

    var lineWidth = 0f

    private val space = 20f


    init {
        paint.color = Color.RED
        paint.isAntiAlias = true
        paint.style = Paint.Style.FILL
        setBackgroundColor(Color.TRANSPARENT)
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        //view根据xml中layout_width和layout_height测量出对应的宽度和高度值，
        val widthSpecMode = MeasureSpec.getMode(widthMeasureSpec)
        val widthSpecSize = MeasureSpec.getSize(widthMeasureSpec)
        when (widthSpecMode) {
            MeasureSpec.UNSPECIFIED -> defaultSize = widthSpecSize
            MeasureSpec.AT_MOST -> defaultSize = getContentWidth()
            MeasureSpec.EXACTLY ->
                defaultSize = max(getContentWidth(), widthSpecSize)
        }
        lineHeight = max(0f, defaultSize - 80f)

        lineWidth = (defaultSize - (count + 1) * space) * 1f / count
        LogUtils.d("宽度:$defaultSize")
        setMeasuredDimension(defaultSize, defaultSize)
    }

    open fun getContentHeight(): Int {
        val contentHeight = height + paddingTop + paddingBottom.toFloat()
        Log.d(ContentValues.TAG, "getContentWidth: contentHeight=$contentHeight")
        return contentHeight.toInt()
    }

    private  fun getContentWidth(): Int {
        val contentWidth = width + paddingLeft + paddingRight.toFloat()
        Log.d(ContentValues.TAG, "getContentWidth: contentWidth=$contentWidth")
        return contentWidth.toInt()
    }

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        canvas?.translate(0f, defaultSize * 1.0f)
        paint.strokeWidth = lineWidth
        val wave = lineHeight
        for (i in 0 until count) {
            val startX = i * (lineWidth + space) + space
            val endY = wave * sin(progress * 360 + startX / defaultSize * 360)
            canvas?.drawLine(startX, 0f, startX, endY.toFloat(), paint)
        }
    }

    override fun onAttachedToWindow() {
        super.onAttachedToWindow()
        startAnimation()
    }

    override fun onDetachedFromWindow() {
        super.onDetachedFromWindow()
        if (valueAnimator != null) {
            valueAnimator.cancel()
        }
    }

    var progress = 0f
    lateinit var valueAnimator: ValueAnimator
    private fun startAnimation() {
        valueAnimator = ValueAnimator.ofFloat(0f, 1f)
        valueAnimator?.duration = 60000
        valueAnimator.interpolator = LinearInterpolator()
        valueAnimator.repeatCount = -1
        valueAnimator.repeatMode = ValueAnimator.REVERSE
        valueAnimator.addUpdateListener {
            progress = it.animatedValue as Float
            postInvalidate()
        }
        valueAnimator.start()
    }

}

利用sin函数实现波浪上下水波起伏