Android UI动态设置带有Stroke渐变色背景Drawable

class StrokeGradientLRDrawable(colors: IntArray,
                               radius: Float,
                               strokeWidth: Float) : ShapeDrawable() {
    init {
        // 外部矩形弧度
        val outerR = floatArrayOf(radius, radius, radius, radius, radius, radius, radius, radius)
        // 内部矩形与外部矩形的距离
        val inset = RectF(strokeWidth, strokeWidth, strokeWidth, strokeWidth)
        // 内部矩形弧度
        val innerRadius = radius - strokeWidth
        val innerRadii = floatArrayOf(innerRadius, innerRadius, innerRadius, innerRadius, innerRadius, innerRadius, innerRadius, innerRadius)
        val rr = RoundRectShape(outerR, inset, innerRadii)
        shape = rr
        shaderFactory = object : ShaderFactory() {
            override fun resize(width: Int, height: Int): Shader {
                return LinearGradient(0f, 0f, width.toFloat(),
                    0f, colors, null, Shader.TileMode.CLAMP)
            }
        }
    }
}

view.background = StrokeGradientLRDrawable(intArrayOf(Color.RED, Color.BLUE), 1000f, 5f)

view.background = StrokeGradientLRDrawable(intArrayOf(Color.RED, Color.BLUE), 50f, 5f)