Android自定义View实现黑客帝国数字雨效果

override fun onDraw(canvas: Canvas?)
{
 super.onDraw(canvas)
 configPaint()
 canvas?.let {

  if (isShowAllNumber())
  {
   drawTotalNumbers(it)
  } else
  {
   drawPartNumbers(it)
  }

 }
}

private fun isShowAllNumber(): Boolean
{
 return nowHeight >= height
}

private fun drawPartNumbers(canvas: Canvas)
{
 val count = (nowHeight / textSize).toInt()
 nowHeight += textSize
 drawNumbers(canvas, count)

}

private fun drawTotalNumbers(canvas: Canvas)
{
 val count = (height / textSize).toInt()
 drawNumbers(canvas, count)
}

private fun drawNumbers(canvas: Canvas, count: Int)
{
 if (count == 0)
 {
  postInvalidateDelayed(startOffset)
 } else
 {
  var offset = 0f
  for (i in 0 until count)
  {
   //生成随机文字
   val text = ((Math.random() * 9).toInt()).toString()
   
   //高亮文字颜色变高亮，否则就是一般颜色
   if (hightLightNumIndex == i)
   {
    paint.color = hightLightColor
    paint.setShadowLayer(10f, 0f, 0f, hightLightColor)

   } else
   {
    paint.color = normalColor
    paint.setShadowLayer(10f, 0f, 0f, normalColor)
   }
   //绘制文字
   canvas.drawText(text, 0f, textSize + offset, paint)
   offset += textSize
  }
   //找到下一个高亮数字的位置
  if (!isShowAllNumber())
  {
   hightLightNumIndex++
  } else
  {
   hightLightNumIndex = (++hightLightNumIndex) % count
  }
  postInvalidateDelayed(100L)
 }
}