Button组件如何设置渐变背景色

@Entry 
@Component 
struct Index { 
  build() { 
    Button('test') 
      .width(200) 
      .height(50) 
      .backgroundColor('#00000000') 
      .linearGradient({ 
        angle: 90, 
        colors: [[0xff0000, 0.0], [0x0000ff, 0.3], [0xffff00, 1.0]] 
      }) 
  } 
}