shaderCallBack function
Implementation
Shader shaderCallBack(Rect rect) => LinearGradient(
stops: const [0.0, 0.15, 0.3, 0.7, 0.85, 1.0],
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
colors: [
Colors.white.withOpacity(0.0),
Colors.white.withOpacity(0.0),
Colors.white,
Colors.white,
Colors.white.withOpacity(0.0),
Colors.white.withOpacity(0.0),
],
).createShader(rect);