_searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0, (self.navigationController.navigationBar.height - 44) / 2.0, 360, 44)];
    [_searchBar setBackgroundImage:[UIImage getImageWithColor:[UIColor clearColor] size:_searchBar.size]];
    [_searchBar setSearchBarStyle:UISearchBarStyleProminent];
    _searchBar.placeholder = @"搜索商品名称/编号/关键字";
    _searchBar.delegate = self;
    _searchBarTF = [_searchBar valueForKey:@"_searchField"];
    UIImageView *topImageView = [_searchBarTF valueForKey:@"_effectBackgroundTop"];// 获取searchBar 有颜色的imageView 可取值（//_effectBackgroundBottom、_effectBackgroundTop、_systemBackgroundView）
    topImageView.image = [UIImage getImageWithColor:[UIColor colorWithHexString:@"DEE0E2"] size:CGSizeMake(1, 1)];
    _searchBarTF.layer.borderWidth = 1;
    _searchBarTF.layer.borderColor = kC7C7C7.CGColor;
    _searchBarTF.layer.cornerRadius = 5;
    _searchBar.tintColor = k009D77;
    _searchBarTF.clipsToBounds = YES;

当UISearchBar为空时也能点击搜索按钮

- (BOOL)searchBar:(UISearchBar *)searchBar shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
    // 不管什么时候都能点击搜索
    UITextField *searchBarTF = [searchBar valueForKey:@"_searchField"];
    searchBarTF.enablesReturnKeyAutomatically = NO;
    return YES;
}

附：kC7C7C7、k009D77 为颜色

+ (UIImage *)getImageWithColor:(UIColor *)color size:(CGSize)size {
    CGRect rect = CGRectMake(0, 0, size.width, size.height);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;

}

+ (UIColor *)colorWithHexString:(NSString *)color {
    NSString *cString = [[color stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];
    
    // String should be 6 or 8 characters
    if ([cString length] < 6) {
        return [UIColor clearColor];
    }
    
    // strip 0X if it appears
    if ([cString hasPrefix:@"0X"])
        cString = [cString substringFromIndex:2];
    if ([cString hasPrefix:@"#"])
        cString = [cString substringFromIndex:1];
    if ([cString length] != 6)
        return [UIColor clearColor];
    
    // Separate into r, g, b substrings
    NSRange range;
    range.location = 0;
    range.length = 2;
    
    //r
    NSString *rString = [cString substringWithRange:range];
    
    //g
    range.location = 2;
    NSString *gString = [cString substringWithRange:range];
    
    //b
    range.location = 4;
    NSString *bString = [cString substringWithRange:range];
    
    // Scan values
    unsigned int r, g, b;
    [[NSScanner scannerWithString:rString] scanHexInt:&r];
    [[NSScanner scannerWithString:gString] scanHexInt:&g];
    [[NSScanner scannerWithString:bString] scanHexInt:&b];
    
    return [UIColor colorWithRed:((float) r / 255.0f) green:((float) g / 255.0f) blue:((float) b / 255.0f) alpha:1.0f];

}