Android Jetpack Compose 中的文本渐变

Question

无法弄清楚如何向具有 的文本添加渐变 inner shadow 在 Jetpack Compose 中带有修饰符。要有这样的东西？有什么想法吗？

Answer 1

到目前为止，jetpack compose 不提供开箱即用的文本渐变和内部阴影。所以需要自己画：

@Composable
fun drawGradientText(name: String, modifier: Modifier = Modifier) {

    val paint = Paint().asFrameworkPaint()

    val gradientShader: Shader = LinearGradientShader(
        from = Offset(0f, 0f),
        to = Offset(0f, 400f),
        listOf(Color.Blue, Color.Cyan)
    )

    Canvas(modifier.fillMaxSize()) {
        paint.apply {
            isAntiAlias = true
            textSize = 400f
            typeface = Typeface.create(Typeface.DEFAULT, Typeface.BOLD)
            style = android.graphics.Paint.Style.FILL
            color = android.graphics.Color.parseColor("#cdcdcd")
            xfermode = PorterDuffXfermode(PorterDuff.Mode.DST_OVER)
            maskFilter = BlurMaskFilter(30f, Blur.NORMAL)
        }
        drawIntoCanvas { canvas ->
            canvas.save()
            canvas.nativeCanvas.translate(2f, 5f)
            canvas.nativeCanvas.drawText(name, 0f, 400f, paint)
            canvas.restore()
            paint.shader = gradientShader
            paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
            paint.maskFilter = null
            canvas.nativeCanvas.drawText(name, 0f, 400f, paint)
            canvas.nativeCanvas.translate(2f, 5f)
            paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.DST_OVER)
            paint.maskFilter = BlurMaskFilter(30f, Blur.NORMAL)
            canvas.nativeCanvas.drawText(name, 0f, 400f, paint)
        }
        paint.reset()
    }
}

您可以调整 PorterDuff 模式和偏移量以满足您的要求。

Answer 2

只是运行进入相同的用例，但只是用于文本上的简单渐变。将其张贴在这里以防对某人有所帮助。

对我有用的是绘制内容，然后通过 Modifier.graphicsLayer 绘制渐变（从 Slack 上的 this 回答推断）：

Text(
   text = "$ 20",
   /** size/font style, etc. **/
   modifier = Modifier.graphicsLayer(alpha = 0.99f)
     .drawWithCache {
        val brush = Brush.horizontalGradient(listOf(StartColor, EndColor))
        onDrawWithContent {
            drawContent()
            drawRect(brush, blendMode = BlendMode.SrcAtop)
        }
     }
)

我最终将其设为 Modifier 以供重复使用：

fun Modifier.textBrush(brush: Brush) = this
   .graphicsLayer(alpha = 0.99f)
   .drawWithCache {
      onDrawWithContent {
         drawContent()
         drawRect(brush, blendMode = BlendMode.SrcAtop)
      }
   }

示例结果：

Android Jetpack Compose 中的文本渐变

Text Gradient in Android Jetpack Compose

android

kotlin

android-jetpack-compose