帮我用Kotlin写一个自定义的进度条，进度条的颜色是渐变色，可以通过代码设置

好的，以下是使用 Kotlin 编写自定义渐变色进度条的代码：

import android.content.Context
import android.graphics.*
import android.util.AttributeSet
import android.view.View

class GradientProgressBar(context: Context, attrs: AttributeSet) : View(context, attrs) {

    private var progress = 0
    private var max = 100
    private var progressColor = intArrayOf(Color.RED, Color.YELLOW, Color.GREEN)

    private val backgroundPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        color = Color.GRAY
    }

    private val progressPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        style = Paint.Style.FILL
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)

        // 绘制背景
        canvas.drawRect(0f, 0f, width.toFloat(), height.toFloat(), backgroundPaint)

        // 绘制进度条
        val progressWidth = progress * width / max.toFloat()
        val progressRect = RectF(0f, 0f, progressWidth, height.toFloat())
        val gradient = LinearGradient(
            0f, 0f, width.toFloat(), 0f,
            progressColor, null, Shader.TileMode.CLAMP
        )
        progressPaint.shader = gradient
        canvas.drawRect(progressRect, progressPaint)
    }

    fun setProgress(progress: Int) {
        this.progress = progress
        invalidate()
    }

    fun setMax(max: Int) {
        this.max = max
        invalidate()
    }

    fun setProgressColor(colors: IntArray) {
        this.progressColor = colors
        invalidate()
    }
}

你可以在代码中设置进度条的颜色，使用 `setProgressColor` 方法即可。