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我有一个在代码中设置的箭头的自定义形状。我想要做的是用渐变填充它。问题是，我不知道如何用渐变填充非矩形形状（暗框内的空间）。有任何想法吗？如何用iOS中的渐变填充用CGPoints定义的形状？
//Define colours used in drawing
CGContextRef context = UIGraphicsGetCurrentContext();
CGColorRef lightColor = _lightColor.CGColor;
CGColorRef darkColor = _darkColor.CGColor;
CGColorRef shadowColor = [UIColor colorWithRed:0.2 green:0.2
blue:0.2 alpha:0.5].CGColor;
//Get label text size to help determine sizes for drawing
CGSize textSize = [[_titleLabel text] sizeWithFont:[_titleLabel font]];
//Set shadow
CGContextSaveGState(context);
CGContextSetShadowWithColor(context, CGSizeMake(0, 2), 3.0, shadowColor);
//Set arrow shape
CGPoint rectangle_points[] =
{
CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y),
CGPointMake(textSize.width+10, _coloredBoxRect.origin.y),
CGPointMake(textSize.width+40, _coloredBoxRect.origin.y+20),
CGPointMake(textSize.width+10, _coloredBoxRect.origin.y+40),
CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y+40),
CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y),
};
CGContextAddLines(context, rectangle_points, 6);
CGContextSetFillColorWithColor(context, lightColor);
CGContextFillPath(context);
CGContextRestoreGState(context);
//Draw dark frame for the arrow
CGContextSetStrokeColorWithColor(context, darkColor);
CGContextSetLineWidth(context, 1.0);
CGContextSaveGState(context);
draw1PxStroke(context, CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y), CGPointMake(textSize.width+10, _coloredBoxRect.origin.y), darkColor);
draw1PxStroke(context, CGPointMake(textSize.width+10, _coloredBoxRect.origin.y+40), CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y+40), darkColor);
draw1PxStroke(context, CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y), CGPointMake(_coloredBoxRect.origin.x, _coloredBoxRect.origin.y+40), darkColor);
draw1PxStroke(context, CGPointMake(textSize.width+10, _coloredBoxRect.origin.y), CGPointMake(textSize.width+40, _coloredBoxRect.origin.y+20), darkColor);
draw1PxStroke(context, CGPointMake(textSize.width+10, _coloredBoxRect.origin.y+40), CGPointMake(textSize.width+40, _coloredBoxRect.origin.y+20), darkColor);
CGContextRestoreGState(context);