ios - 在 drawRect 中将文本放在其他 CALayer 之上

Question

我试图在 CALayer 上方显示文本，但不知何故我无法实现它。我使用了以下代码:

- (void)drawRect:(CGRect)rect
{
    self.layer.sublayers = nil;
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSaveGState(ctx);

    // Code to show grid lines clipped

    CGRect overallRectForBarItem = CGRectMake(20, 20, 176, 35);
    CAShapeLayer *barItemShape = [CAShapeLayer layer];
    barItemShape.frame = overallRectForBarItem;
    barItemShape.path = [UIBezierPath bezierPathWithRect:overallRectForBarItem].CGPath;
    barItemShape.strokeColor = [UIColor lightGrayColor].CGColor;
    barItemShape.fillColor = [UIColor lightGrayColor].CGColor;
    [self.layer addSublayer:barItemShape];

    [self drawTextForBarItem:@"TESTING" inRect:CGRectMake(100, 40, 35, 0)];

    // Other code clipped

    CGContextRestoreGState(ctx);
}

-(void) drawTextForBarItem:(NSString*)barItemTitle inRect:(CGRect)rect
{
    float actualFontSize = 14.0;
    UIFont *font = [ISUtility getSystemFont:actualFontSize];
    CGSize size = [barItemTitle sizeWithFont:font];
    NSMutableParagraphStyle *paragraphStyle = [[[NSParagraphStyle defaultParagraphStyle] mutableCopy] autorelease];
    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
    paragraphStyle.alignment = NSTextAlignmentRight;
    [barItemTitle drawInRect:CGRectMake(rect.origin.x, rect.origin.y - size.height/2, rect.size.width, size.height) withAttributes:@{NSFontAttributeName:font, NSForegroundColorAttributeName:[UIColor blueColor], NSParagraphStyleAttributeName:paragraphStyle}];
}

以下是模拟器的截图。

我也试过 zPosition 但没用。

barItemShape.zPosition = -1000;

Answer 1

问题的最可能原因是您创建了 CGContextRef 但在需要绘制浅灰色矩形时添加了子层。我认为，使用 CoreGraphics 函数绘制矩形和绘制文本会更加一致。

更详细地说，您似乎在当前图层中绘制文本，但添加的子图层将位于您的文本之上。

例如，您可以使用这段代码来尝试一下:

UIColor * redColor = [UIColor colorWithRed:1.0 green:0.0 blue:0.0 alpha:1.0];

CGContextSetFillColorWithColor(context, redColor.CGColor);
CGContextFillRect(context, self.bounds);