Add inner shadow to uiview.

inner_shadow

- (void)drawRect:(CGRect)rect {
  [[UIImage imageNamed:@"top_bg_pattern.png"] drawAsPatternInRect:rect];
  [self drawShadowsWithHeight:10 opacity:0.3 InRect:rect forContext:UIGraphicsGetCurrentContext()];
}

- (void)drawShadowsWithHeight:(CGFloat)shadowHeight opacity:(CGFloat)opacity InRect:(CGRect)rect forContext:(CGContextRef)context {

  CGColorSpaceRef space = CGBitmapContextGetColorSpace(context);

	CGFloat topComponents[8] = {0, 0, 0, opacity, 0, 0, 0, 0};
	CGGradientRef topGradient = CGGradientCreateWithColorComponents(space, topComponents, nil, 2);
	CGPoint finishTop = CGPointMake(rect.origin.x, rect.origin.y + shadowHeight);
	CGContextDrawLinearGradient(context, topGradient, rect.origin, finishTop, kCGGradientDrawsAfterEndLocation);

	CGFloat bottomComponents[8] = {0, 0, 0, 0, 0, 0, 0, opacity};
	CGGradientRef bottomGradient = CGGradientCreateWithColorComponents(space, bottomComponents, nil, 2);
	CGPoint startBottom = CGPointMake(rect.origin.x, rect.size.height - shadowHeight);
	CGPoint finishBottom = CGPointMake(rect.origin.x, rect.size.height);
	CGContextDrawLinearGradient(context, bottomGradient, startBottom, finishBottom, kCGGradientDrawsAfterEndLocation);

	CGGradientRelease(topGradient);
	CGGradientRelease(bottomGradient);
}