iphone - iOS:在 UIView 中绘制阴影

Question

我发现了一些很棒的代码，它们是 UIView 的子类，它用阴影绘制该 View 。然后我可以在任何想要放置阴影的地方使用该 View :

-(void) layoutSubviews {
    CGFloat coloredBoxMargin = 40;
    CGFloat coloredBoxHeight = self.frame.size.height;
    _coloredBoxRect = CGRectMake(coloredBoxMargin, 0, 40, coloredBoxHeight);
}

-(void) drawRect:(CGRect)rect {

    CGColorRef lightColor =  [UIColor colorWithRed:105.0f/255.0f green:179.0f/255.0f blue:216.0f/255.0f alpha:0.8].CGColor;
    CGColorRef shadowColor = [UIColor colorWithRed:0.2 green:0.2 blue:0.2 alpha:0.4].CGColor;   

    CGContextRef context = UIGraphicsGetCurrentContext();
    // Draw shadow
    CGContextSaveGState(context);
    CGContextSetFillColorWithColor(context, lightColor);
    CGContextSetShadowWithColor(context, CGSizeMake(-13, 0), 10, shadowColor);

    CGContextFillRect(context, _coloredBoxRect);
    CGContextRestoreGState(context);
}

使用以下内容创建:

UIViewWithShadowRight* verticalLineView2 = [[[UIViewWithShadowRight alloc] initWithFrame:CGRectMake(60, 0, 40 , self.view.frame.size.height)] autorelease];
[verticalLineView2 setBackgroundColor:[UIColor clearColor]];
[verticalLineView2 setAutoresizingMask:UIViewAutoresizingFlexibleHeight];
[verticalLineView2 setClipsToBounds:NO];
[self.view addSubview:verticalLineView2];
[self.view bringSubviewToFront:verticalLineView2];

问题是，阴影是从右向左绘制的，如何反转它并从左向右绘制？

Answer 1

将13设为正数而不是负数。这是绘制阴影的 x 偏移量，负值位于原始绘图的左侧，正值位于原始绘图的右侧。