隐形导航栏

Question

是否可以有一个不可见的导航栏背景？我以前见过定制的，但希望得到一些关于如何做到这一点的指导。

提前致谢！

Answer 1

要在 UINavigationBar 或 UIToolbar 上获得透明背景，您必须将背景颜色设置为 [UIColor clearColor]，将 opaque 设置为 NO（如果尚未设置） ，并重写drawRect以不绘制标准渐变背景。第三是棘手的部分。

如果您直接使用 UINavigationBar，则只需对其进行子类化即可轻松覆盖 drawRect。但我看到您用 UINavigationController 标记了它，因此您必须尝试用类别覆盖它。像这样的事情应该可以做到：

@implementation UINavigationBar (invisibleBackground)

- (void)drawRect:(CGRect)rect {}

@end

它的缺点是应用程序中的每个导航栏现在都没有背景。如果你希望能够有一些透明和一些正常，你必须更进一步并混合 drawRect 以便你可以在需要时调用原始的：

#import <objc/runtime.h>

@implementation UINavigationBar (invisibleBackgroundSwizzle)

// The implementation of this method will be used to replace the stock "drawRect:". The old
// implementation of "drawRect:" will be attached to this name so we can call it when needed.
- (void)replacementDrawRect:(CGRect)rect {
    if (![self.backgroundColor isEqual:[UIColor clearColor]]) {
        // Non-transparent background, call the original method (which now exists
        // under the name "replacementDrawRect:"). Yes, it's a bit confusing.
        [self replacementDrawRect:rect];
    } else {
        // Transparent background, do nothing
    }
}

// This special method is called by the runtime when this category is first loaded.
+ (void)load {
    // This code takes the "drawRect:" and "replacementDrawRect:" methods and switches
    // thier implementations, so the name "drawRect" will now refer to the method declared as
    // "replacementDrawRect:" above and the name "replacementDrawRect:" will now refer
    // to the original implementation of "drawRect:".
    Method originalMethod = class_getInstanceMethod(self, @selector(drawRect:));
    Method overrideMethod = class_getInstanceMethod(self, @selector(replacementDrawRect:));
    if (class_addMethod(self, @selector(drawRect:), method_getImplementation(overrideMethod), method_getTypeEncoding(overrideMethod))) {
        class_replaceMethod(self, @selector(replacementDrawRect:), method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
    } else {
        method_exchangeImplementations(originalMethod, overrideMethod);
    }
}

@end

Answer 2

就在今天，我自己（再次）查找了这个内容，有关此主题的一些不错的博客文章是：

http://idevrecipes.com/2011/01/12 /how-do-iphone-apps-instagramreederdailybooth-implement-custom-navigationbar-with-variable-width-back-buttons/