iPhone X的tabbar push时图片下移问题

适配iPhone X时出现了以下问题

左侧为正常效果；右侧为iPhone Xpresent后dismiss回来，然后再push后的效果

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估计的原因是iPhone X上tabbar的高度由原来的49变为83，但是在UITabBarController中只有在viewdidAppear以后才能获取到正确的高度，而自定义的tabbar中是可以根据iOS11的safeAreaInsetsDidChange方法重新设置

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后来改了好久，终于在stack overflow上找到了解决办法，链接地址：https://stackoverflow.com/questions/46232929/why-page-push-animation-tabbar-moving-up-in-the-iphone-x/47225653#4722565

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解决办法如下，新建一个类wls_baseTabbar继承自UITabbar

wls_baseTabbar.m 文件

#import "tgq_baseTabbar.h"

@implementation tgq_baseTabbar

{

       UIEdgeInsets oldSafeAreaInsets;

}

- (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

然后在你自定义的UITabBarController中

- (void)viewDidLoad {

[super viewDidLoad];

//1.设置tabbar

tgq_baseTabbar *bar = [[tgq_baseTabbar alloc] init]

[self setValue:bar forKey:@"tabBar"];

//2.添加子控制器

[self setChildVC];

}