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

2020-07-26 02:28:16

字體：大中小

來源：轉載

供稿：網友

方法一：設置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：

要給整個backButtonItem賦值才可以，👇這種方法不行，因為backBarButtonItem默認為空，給nil方法消息，默認聲明都不執行（參考官網）

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

leftBarButtonItem 與backBarButtonItem 的顯示關系：

有leftBarButtonItem則優先顯示當前VC的leftBarButtonItem，無則顯示上個VC的backBarButtonItem，再無則顯示上個VC的title（參考官網還是官網解釋的清楚）