iOS 11 使用方法替換(Method Swizzling)，去掉導覽列返回按鈕的文字

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    方法一：設定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不能置中，被位移很多，如下所示（雖然不被顯示，也佔了導覽列左邊很大一部分位置）

 

     方法二：給UIViewController添加類別，然後在load方法裡面用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預設為空白，給nil方法訊息，預設聲明都不執行（參考官網）

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

 

• leftBarButtonItem 與backBarButtonItem 的顯示關係：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）

 

 

 

iOS 11 使用方法替換(Method Swizzling)，去掉導覽列返回按鈕的文字