值不在 UISlider 的拇指范围内

Question

这是我用来显示拇指图像内滑块值的代码。但该值仍然显示在滑块下方。请帮我。

-(IBAction)sliderValueChanged:(id)sender 
{
    UISlider *aSlider = (UISlider *)sender;
    [aSlider setThumbImage:
        [self addText:self.thumbImage text:[NSString stringWithFormat:@"%.0f",
        aSlider.value * 100]] forState:aSlider.state];
}

//Add text to UIImage 

-(UIImage *)addText:(UIImage *)img text:(NSString *)text1{ 
    int w = img.size.width; 
    int h = img.size.height; 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, 
        colorSpace, kCGImageAlphaPremultipliedFirst); 
    CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage); 

    char* text= (char *)[text1 cStringUsingEncoding:NSASCIIStringEncoding]; 
    CGContextSelectFont(context, "Arial",12, kCGEncodingMacRoman); 
    CGContextSetTextDrawingMode(context, kCGTextFill); 
    CGContextSetRGBFillColor(context, 0, 0, 0, 1); 
    CGContextShowTextAtPoint(context,3,8,text, strlen(text)); 
    CGImageRef imgCombined = CGBitmapContextCreateImage(context); 

    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace); 

    UIImage *retImage = [UIImage imageWithCGImage:imgCombined]; 
    CGImageRelease(imgCombined); 

    return retImage;