浅谈Xcode9 和iOS11适配和特性

　　- (void)resetSearchBar

　　{

　　CGFloat leftButtonWidth = 35, rightButtonWidth = 75; // left padding right padding

　　UIView *container = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width - leftButtonWidth - rightButtonWidth, 44)];

　　self.searchBar.translatesAutoresizingMaskIntoConstraints = NO;

　　[container addSubview:self.searchBar];

　　CGFloat offset = (rightButtonWidth - leftButtonWidth) / 2;

　　// 给searchBar添加约束

　　[NSLayoutConstraint activateConstraints:@[

　　[self.searchBar.topAnchor constraintEqualToAnchor:container.topAnchor], // 顶部约束

　　[self.searchBar.leftAnchor constraintEqualToAnchor:container.leftAnchor constant:-25*ScreenScaleX], // 左边距约束

　　[self.searchBar.rightAnchor constraintEqualToAnchor:container.rightAnchor constant:0], // 右边距约束

　　[self.searchBar.bottomAnchor constraintEqualToAnchor:container.bottomAnchor], // 底部约束

　　[self.searchBar.centerXAnchor constraintEqualToAnchor:container.centerXAnchor constant:-offset], // 横向中心约束

　　// [self.searchBar.widthAnchor constraintEqualToAnchor:container.widthAnchor constant:width] // 宽度约束

　　]];

　　self.navigationItem.titleView = container; // 顶部导航搜索

　　}