輸入相關關鍵字在百度中能搜尋出來很多，但是都不靠譜，於是Google了一下，在StackOverFlow中找到一個蠻靠譜的方法，試了可行。

with iOS8 sdks apple moved @"UISearchBarBackground" view one level deeper, so have will need to look at subviews of the child-views as bellow,.

for (UIView *subview in searchBar.subviews) {
        for(UIView* grandSonView in
 
 subview.subviews){
            if ([grandSonView isKindOfClass:NSClassFromString(@"UISearchBarBackground")]) {
                grandSonView.alpha = 0.0f;
            }else if([grandSonView isKindOfClass:NSClassFromString(@"UISearchBarTextField")] ){
                NSLog(@"Keep textfiedld bkg color");
            }
 
else{
                grandSonView.alpha = 0.0f;
            }
        }//for cacheViews
    }//subviews

耶！

接下來，我又發現一位博主分享的文章，寫的很詳細，而且解決方案看起來會更加優雅，不像上面給的那樣暴力粗魯。^_^

文章在這裡。

這裡貼出程式碼：

- (void)viewDidLoad
{
    [super viewDidLoad];
    // 1
    UIImage* clearImg = [CDViewController imageWithColor:[UIColor clearColor] andHeight:32.0f
 
];
    // 2
    [_searchBar setBackgroundImage:clearImg];
    // 3
    [_searchBar setSearchFieldBackgroundImage:clearImg forState:UIControlStateNormal];
    // 4
    [_searchBar setBackgroundColor:[UIColor clearColor]];
}

+ (UIImage*) imageWithColor:(UIColor*)color andHeight:(CGFloat)height
{
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, height);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);

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

    return image;
}

修改APP內全域性UISearchBar樣式：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UIColor* myColor = [UIColor colorWithRed:0 green:0.48 blue:1 alpha:1]; // set your desired background color here

    UIImage* clearImg = [CDViewController imageWithColor:[UIColor clearColor] andHeight:1.0f];
    UIImage* coloredImg = [CDViewController imageWithColor:myColor andHeight:32.0f];

    [[UISearchBar appearance] setBackgroundColor:[UIColor clearColor]];
    [[UISearchBar appearance] setBackgroundImage:clearImg];
    [[UISearchBar appearance] setSearchFieldBackgroundImage:coloredImg forState:UIControlStateNormal];

    return YES;
}

給ScopeBar設定透明背景：

UIImage* clearImg = [CDViewController imageWithColor:[UIColor clearColor] andHeight:1.0f];

[_searchBar setScopeButtonTitles:nil];
[_searchBar setScopeBarBackgroundImage:clearImg];
[_searchBar setScopeBarButtonBackgroundImage:clearImg forState:UIControlStateNormal];
[_searchBar setScopeBarButtonDividerImage:clearImg forLeftSegmentState:UIControlStateNormal rightSegmentState:UIControlStateNormal];

http://www.cnblogs.com/emmet7life/p/4648383.html