前言

在iPhone X設備帶有tabBar的頁面，如果控制器的hidesBottomBarWhenPushed屬性為YES，進行push操作之后，便會出現如下的一些問題，于是我查看了一次蘋果系統的一些應用，發現它們是不隱藏tabBar的，估計是蘋果就是不希望我們去隱藏它的tabBar。

demo下載

點擊下載demo源代碼

問題描述：

1、iPhone X push后，tabBar偏移

異常顯示效果：

直接push.png

2、iPhone X modal并返回之后， 再push后，tabBar偏移

在帶有tabBar的頁面，模態彈出（presentViewController）并返回后，再任意執行push操作，便會出現如下異常
異常顯示效果：

modal后push.png

解決問題：

1、自定義的BaseTabBar

創建自定義的BaseTabBar，繼承自UITabBar，替換TabBarController的tabBar，代碼如下：

YUBaseTabBar *baseTabBar = [[YUBaseTabBar alloc] init];
[self setValue:baseTabBar forKey:@"tabBar"];

2、重寫tabBar的一些方法

OC代碼

#import "YUBaseTabBar.h"

@implementation YUBaseTabBar
{
   UIEdgeInsets _oldSafeAreaInsets;
}

- (instancetype)initWithFrame:(CGRect)frame
{
   self = [super initWithFrame:frame];
   if (self) {
       _oldSafeAreaInsets = UIEdgeInsetsZero;
   }
   return self;
}

- (void)awakeFromNib {
   [super awakeFromNib];
   
   _oldSafeAreaInsets = UIEdgeInsetsZero;
}

- (void)safeAreaInsetsDidChange {
   [super safeAreaInsetsDidChange];
   
   if (!UIEdgeInsetsEqualToEdgeInsets(_oldSafeAreaInsets, self.safeAreaInsets)) {
       [self invalidateIntrinsicContentSize];
       
       if (self.superview) {
           [self.superview setNeedsLayout];
           [self.superview layoutSubviews];
       }
   }
}

- (CGSize)sizeThatFits:(CGSize)size {
   size = [super sizeThatFits:size];
   
   if (@available(iOS 11.0, *)) {
       float bottomInset = self.safeAreaInsets.bottom;
       if (bottomInset > 0 && size.height < 50 && (size.height + bottomInset < 90)) {
           size.height += bottomInset;
       }
   }
   
   return size;
}


- (void)setFrame:(CGRect)frame {
   if (self.superview) {
       if (frame.origin.y + frame.size.height != self.superview.frame.size.height) {
           frame.origin.y = self.superview.frame.size.height - frame.size.height;
       }
   }
   [super setFrame:frame];
}

@end

swift代碼

class YUBaseTabBar: UITabBar {

var oldSafeAreaInsets = UIEdgeInsets.zero

@available(iOS 11.0, *)
override func safeAreaInsetsDidChange() {
   super.safeAreaInsetsDidChange()

   if oldSafeAreaInsets != safeAreaInsets {
       oldSafeAreaInsets = safeAreaInsets

       invalidateIntrinsicContentSize()
       superview?.setNeedsLayout()
       superview?.layoutSubviews()
   }
}

override func sizeThatFits(_ size: CGSize) -> CGSize {
   var size = super.sizeThatFits(size)
   if #available(iOS 11.0, *) {
       let bottomInset = safeAreaInsets.bottom
       if bottomInset > 0 && size.height < 50 && (size.height + bottomInset < 90) {
           size.height += bottomInset
       }
   }
   return size
}

override var frame: CGRect {
   get {
       return super.frame
   }
   set {
       var tmp = newValue
       if let superview = superview, tmp.maxY != 
       superview.frame.height {
           tmp.origin.y = superview.frame.height - tmp.height
       }

       super.frame = tmp
       }
   }
}
}

demo查看（https://github.com/timelywind/TabBarFit_iPhoneX_Demo）

參考：https://stackoverflow.com/a/47225653/1553324

謝謝！