我怎样才能画画Path
带有褪色(不透明度或粗细)线?像这样的东西。
我知道有LinearGradient
着色器Paint
,但不会bend沿着Path
.
一种可能的解决方案可能是沿着Path
然后我自己通过分段来绘制它。但我也找不到任何方法。
我想出了以下代码。最重要的是PathMeasure's getPosTan() method https://developer.android.com/reference/android/graphics/PathMeasure.html#getPosTan(float,%20float%5B%5D,%20float%5B%5D).
if (getGesturePath() != null) {
final short steps = 150;
final byte stepDistance = 5;
final byte maxTrailRadius = 15;
pathMeasure.setPath(getGesturePath(), false);
final float pathLength = pathMeasure.getLength();
for (short i = 1; i <= steps; i++) {
final float distance = pathLength - i * stepDistance;
if (distance >= 0) {
final float trailRadius = maxTrailRadius * (1 - (float) i / steps);
pathMeasure.getPosTan(distance, pathPos, null);
final float x = pathPos[0] + RandomUtils.nextFloat(0, 2 * trailRadius) - trailRadius;
final float y = pathPos[1] + RandomUtils.nextFloat(0, 2 * trailRadius) - trailRadius;
paint.setShader(new RadialGradient(
x,
y,
trailRadius > 0 ? trailRadius : Float.MIN_VALUE,
ColorUtils.setAlphaComponent(Color.GREEN, random.nextInt(0xff)),
Color.TRANSPARENT,
Shader.TileMode.CLAMP
));
canvas.drawCircle(x, y, trailRadius, paint);
}
}
}
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