安卓TextView调整下划线颜色、与文本底部的距离

需要自定义view来实现，因为安卓的TextView没有提供设置颜色与间距的方法

实现效果

下划线颜色与文字不一样
下划线距离文字底部的边界可调整
但只能标记同一行的文字，也就是说下划线的start与end在同一行。还没多行的需求，有时间再说

package com.XXX

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.Rect
import android.util.AttributeSet
import android.util.Log
import androidx.annotation.ColorRes
import androidx.appcompat.widget.AppCompatTextView
import androidx.core.content.ContextCompat
import com.XXX.R

/**
 * 设置下划线，支持设置下划线颜色、文本底部矩形边界与下划线的间距；下划线仅支持展示在一行
 */
class OnSameLineUnderLineTextView @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : AppCompatTextView(context, attrs, defStyleAttr) {

    private var start: Int = 0
    private var end: Int = 0
    private var widthDp: Float = 1f
    private var colorRes: Int = R.color.black
    private var offsetOfY: Float = 0f

    /**
     * 给文字设置下划线
     * @param   start 下划线初始字符的索引
     *          end   下划线结束字符的索引
     *          widthDp 下划线的高度
     *          colorRes 颜色
     *          offsetOfY 底部边界
     */
    fun drawUnderLine(start: Int,
                      end: Int,
                      widthDp: Float = this.widthDp,
                      @ColorRes colorRes: Int = this.colorRes,
                      offsetOfY: Float = 0f) {
        this.start = start
        this.end = end
        this.widthDp = widthDp
        this.colorRes = colorRes
        this.offsetOfY = offsetOfY
        invalidate()
      
    }


    @SuppressLint("DrawAllocation")
    override fun onDraw(canvas: Canvas) {

        if (this.start >= this.end) return

        val paint = Paint()
        paint.color = ContextCompat.getColor(context, this.colorRes)
        paint.strokeWidth = widthDp

        //只有同一行生效
        val lineStart = layout.getLineForOffset(start)
        val lineEnd = layout.getLineForOffset(end)

        if (lineStart == lineEnd) {
            val bound = Rect()
            layout.getLineBounds(lineStart, bound)

            val startXBottom = layout.getPrimaryHorizontal(start)
            val startYBottom = bound.bottom.toFloat()

            val endXBottom = layout.getSecondaryHorizontal(end)
            val endYBottom = bound.bottom.toFloat()

            canvas.drawLine(startXBottom, startYBottom + offsetOfY, endXBottom, endYBottom + offsetOfY, paint)
        } else {
        	//待实现多行逻辑
        }

        super.onDraw(canvas)
    }
}

调用

//你的字符串，注意需要下划线的那段文字需要在同一行！！我是直接在差不多的位置加的"\n"
val baseString = itemView.context.getString(bean.content)
//需要下划线的那段字
val lineString = itemView.context.getString(bean.contentSub)
//找到需下划线文字的开头索引
val indexOf = baseString.indexOf(lineString)
if (indexOf >= 0) {
	//给textview加6dp，指定颜色的下划线，
    mProductTitle.drawUnderLine(indexOf, indexOf + lineString.length,
        SmartUtil.dp2px(6f).toFloat(), bean.contentSubUnderLineColorRes,
        SmartUtil.dp2px(-9f).toFloat()
    )
}

那个-9是怎么来的？

最后说一下上面调用的代码中第五个参数传“-9”是怎么来的

mProductTitle.drawUnderLine(indexOf, indexOf + lineString.length,
        SmartUtil.dp2px(6f).toFloat(), bean.contentSubUnderLineColorRes,
        SmartUtil.dp2px(-9f).toFloat()
    )