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iOS 11 使用兩種方法替換(Method Swizzling)去掉導(dǎo)航欄返回按鈕的文字

更新時間：2018年05月07日 10:36:40 作者：星紅

這篇文章主要介紹了iOS 11 使用方法替換(Method Swizzling)去掉導(dǎo)航欄返回按鈕的文字,需要的朋友可以參考下

方法一：設(shè)置BarButtonItem的文本樣式為透明顏色，代碼如下：

[[UIBarButtonItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName: [UIColor clearColor]} forState:UIControlStateNormal]; 
[[UIBarButtonItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName: [UIColor clearColor]} forState:UIControlStateHighlighted];

此外這種方法會導(dǎo)致title不能居中，被偏移很多，如下所示（雖然不被顯示，也占了導(dǎo)航欄左邊很大一部分位置）

方法二：給UIViewController添加類別，然后在load方法里面用Method Swzilling方法替換交換ViewDidAppear，部分代碼如下

+(void)load {
  swizzleMethod([self class], @selector(viewDidAppear:), @selector(ac_viewDidAppear));
}
- (void)ac_viewDidAppear{
  self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc]
                       initWithTitle:@""
                       style:UIBarButtonItemStylePlain
                       target:self
                       action:nil];
  [self ac_viewDidAppear];
}
void swizzleMethod(Class class, SEL originalSelector, SEL swizzledSelector)
{
  // the method might not exist in the class, but in its superclass
  Method originalMethod = class_getInstanceMethod(class, originalSelector);
  Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
  // class_addMethod will fail if original method already exists
  BOOL didAddMethod = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
  // the method doesn't exist and we just added one
  if (didAddMethod) {
    class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
  }
  else {
    method_exchangeImplementations(originalMethod, swizzledMethod);
  }
}

注意事項(xiàng)：

要給整個backButtonItem賦值才可以，👇這種方法不行，因?yàn)閎ackBarButtonItem默認(rèn)為空，給nil方法消息，默認(rèn)聲明都不執(zhí)行（參考官網(wǎng)）

self.navigationItem.backBarButtonItem.title = @" ";

leftBarButtonItem 與backBarButtonItem 的顯示關(guān)系：

有l(wèi)eftBarButtonItem則優(yōu)先顯示當(dāng)前VC的leftBarButtonItem，無則顯示上個VC的backBarButtonItem，再無則顯示上個VC的title（參考官網(wǎng) 還是官網(wǎng)解釋的清楚）