原文鏈接

創建一個UINavigationBar的分類
UINavigationBar+CustomHeight.h

@interface UINavigationBar (CustomHeight)

- (void)setHeight:(CGFloat)height;

@end

UINavigationBar+CustomHeight.m

#import "objc/runtime.h"

static char const *const heightKey = "Height";

@implementation UINavigationBar (CustomHeight)

- (void)setHeight:(CGFloat)height
{
    objc_setAssociatedObject(self, heightKey, @(height), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSNumber *)height
{
    return objc_getAssociatedObject(self, heightKey);
}

- (CGSize)sizeThatFits:(CGSize)size
{
    CGSize newSize;
    
    if (self.height) {
        newSize = CGSizeMake(self.superview.bounds.size.width, [self.height floatValue]);
    } else {
        newSize = [super sizeThatFits:size];
    }

    return newSize;
}

@end

使用方法

在-(void)viewWillAppear:(BOOL)animated方法里面添加

UINavigationBar *bar = self.navigationController.navigationBar;
[bar setHeight:88];

在-(void)viewWillDisappear:(BOOL)animated方法里面添加

UINavigationBar *bar = self.navigationController.navigationBar;
[bar setHeight:44];

這樣我們就可以看到這樣的界面了

屏幕快照 2017-05-16.png

what？？導航欄的標題往下移動了？
這也許不是我們想要的界面。
我們可能需要調整導航欄的標題和按鈕的位置了

-(void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    CGRect rect = self.navigationController.navigationBar.frame;
    UINavigationBar *bar = self.navigationController.navigationBar;
    [bar setHeight:88];
  
  //調整導航欄標題的位置  
  [bar setTitleVerticalPositionAdjustment:-44 forBarMetrics:UIBarMetricsDefault];

   //調整導航欄按鈕的位置
   UIBarButtonItem *item = self.navigationItem.leftBarButtonItem;
   [item setBackgroundVerticalPositionAdjustment:-44 forBarMetrics:UIBarMetricsDefault];
}