着色器ShaderMask
说明
实现一个渐变进度条，要求：
颜色渐变的过程是循序渐进的，而不是看起来像是将渐变条逐渐拉长了。
效果
源码
// 渐变进度条Stack(children: [// 背景色板Container(width: 300,height: 8,decoration: BoxDecoration(borderRadius: BorderRadius.circular(12),color: Colors.grey.withOpacity(0.15)),),// 着色ClipRRect(borderRadius: BorderRadius.circular(12),// ShaderMask 着色器child: ShaderMask(// BlendMode 多种模式可选//【BlendMode介绍】https://blog.csdn.net/chenlove1/article/details/84574237blendMode: BlendMode.srcOver, // srcOver ：将 源 合成到 目标上shaderCallback: (Rect bounds) {// 源图像return const LinearGradient(colors: [Color(0xFF7451ff), Color(0xff40d0fd)],).createShader(const Rect.fromLTWH(0, 0, 300, 8));},// 目标图像child: AnimatedContainer(width: 200, // 进度height: 8,duration: Durations.medium1,decoration: BoxDecoration(borderRadius: BorderRadius.circular(12),color: Colors.grey.withOpacity(0.15),),),),)],)