设置iphone中的UIToolbar的颜色

在ios4.3以上版本，想把UIToolbar的颜色改成灰色，

但是下面的代码没有实现：

- (void)drawRect:(CGRect)rect {

    UIGraphicsBeginImageContext(rect.size);

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSaveGState(ctx);

        [[UIColor colorWithRed:64.0f/255.0f
                         green:64.0f/255.0f
                          blue:64.0f/255.0f
                         alpha:1.0f] set];

    CGRect myRect = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
    CGContextFillRect(ctx, myRect);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    CGContextRestoreGState(ctx);
    UIGraphicsEndImageContext();

    [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

为什么？

可以通过使用灰色的背景图片实现。用下面代码加入图片：

   UIToolbar *toolBar = //此处添加toolbar

    UIImage *toolbarBkg = [[UIImage imageNamed: @"toolbarBkg.png"] stretchableImageWithLeftCapWidth:0 topCapHeight:0];

    if ([toolBar respondsToSelector:@selector(setBackgroundImage:forToolbarPosition:barMetrics:)])
        [toolBar setBackgroundImage:toolbarBkg forToolbarPosition:UIToolbarPositionAny barMetrics:UIBarMetricsDefault];
    else {
        UIImageView *background = [[UIImageView alloc] initWithImage:toolbarBkg];
        background.frame = toolBar.frame;
        [toolBar insertSubview:background atIndex:0];
    }