RadialGradient gradient = new RadialGradient(j/2,k/2,j/2,new int[]{0xff5d5d5d,0xff5d5d5d,0x00ffffff},new float[]{0.f,0.8f,1.0f}, Shader.TileMode.CLAMP);paint.setShader(gradient);canvas.drawCircle(j/2,k/2,j/2,paint);

/** * 轉換圖片成圓形 * @param bitmap 傳入Bitmap對象 * @return */ public Bitmap toRoundBitmap(Bitmap bitmap) {  int width = bitmap.getWidth();  int height = bitmap.getHeight();  float roundPx;  float left,top,right,bottom,dst_left,dst_top,dst_right,dst_bottom;  if (width <= height) {   roundPx = width / 2 -5;   top = 0;   bottom = width;   left = 0;   right = width;   height = width;   dst_left = 0;   dst_top = 0;   dst_right = width;   dst_bottom = width;  } else {   roundPx = height / 2 -5;   float clip = (width - height) / 2;   left = clip;   right = width - clip;   top = 0;   bottom = height;   width = height;   dst_left = 0;   dst_top = 0;   dst_right = height;   dst_bottom = height;  }   Bitmap output = Bitmap.createBitmap(width,    height, Bitmap.Config.ARGB_8888);  Canvas canvas = new Canvas(output);   final int color = 0xff424242;  final Paint paint = new Paint();  final Rect src = new Rect((int)left, (int)top, (int)right, (int)bottom);  final Rect dst = new Rect((int)dst_left, (int)dst_top, (int)dst_right, (int)dst_bottom);  final RectF rectF = new RectF(dst_left+15, dst_top+15, dst_right-20, dst_bottom-20);   paint.setAntiAlias(true);   canvas.drawARGB(0, 0, 0, 0);  paint.setColor(color);   canvas.drawRoundRect(rectF, roundPx, roundPx, paint);   paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));  canvas.drawBitmap(bitmap, src, dst, paint);  return output; }

Paint paint = new Paint();   paint.setColor(0xffffffff);   paint.setStrokeWidth(10);   paint.setStyle(Paint.Style.STROKE);    canvas.drawCircle(j/2,k/2,j/2-20,paint);