利用 Objetive-c Category 特性 更换 UINavigationBar 背景

@implementation UINavigationBar (UINavigationBarCategory)- (void)drawRect:(CGRect)rect {//颜色填充//UIColor *color = [UIColor redColor];//CGContextRef context = UIGraphicsGetCurrentContext();//CGContextSetFillColor(context, CGColorGetComponents( [color CGColor]));//CGContextFillRect(context, rect);//self.tintColor = color;//图片填充UIColor *color = [UIColor colorWithRed:46.0f/255.0f green:87.0f/255.0f blue:29.0f/255.0f alpha:1.0f];UIImage *img= [UIImage imageNamed: @"bg.png"];[img drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];self.tintColor = color;}@end

目前按钮无法设置透明只有纯色背景。