/**
   @param centerX   中心X坐標(biāo)
   @param centerY   中心Y坐標(biāo)
   @param radius   半徑
   @param centerColor 開(kāi)始顏色
   @param edgeColor  結(jié)束顏色
   @param tileMode  The Shader tiling mode
   */
  public RadialGradient(float centerX, float centerY, float radius,int centerColor, int edgeColor, @NonNull TileMode tileMode)


 public RadialGradient(float centerX, float centerY, float radius,@NonNull int colors[], @Nullable float stops[], @NonNull TileMode tileMode)

RadialGradient rg = new RadialGradient(canvas.getWidth()/2, canvas.getHeight()/2, 200, 0xffff0000, 0xff0000ff, Shader.TileMode.[CLAMP|REPEAT |MIRROR]);
    paint.setShader(rg);
    canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);

/**
  *
  * @param cx  中心X坐標(biāo)
  * @param cy  中心Y坐標(biāo)
  * @param color0 開(kāi)始顏色
  * @param color1 結(jié)束顏色
  */
 public SweepGradient(float cx, float cy, int color0, int color1)

 public SweepGradient(float cx, float cy,int colors[], float positions[])

int[] colors = {0xffff0000, 0xff00ff00, 0xffffff00, 0xffffffff,0xff000000};
float[] positions = {0f,0.25f, 0.5f, 0.75f, 1f};
SweepGradient rg = new SweepGradient(canvas.getWidth() / 2, canvas.getHeight() / 2, colors, positions);
paint.setShader(rg);
canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);

ComposeShader(Shader shaderA, Shader shaderB, Xfermode mode)
ComposeShader(Shader shaderA, Shader shaderB, PorterDuff.Mode mode)