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[操作系统]系统在某些情况下会自动调节UIScrollView的contentInset


 

    出现情景

    如果一个控制器(ViewController)被导航控制器管理,并且该控制器的第一个子控件是UIScrollView,系统默认会调节UIScrollView的contentInset

  UIEdgeInsetsMake(64, 0, 0, 0) // 有导航栏

  UIEdgeInsetsMake(20, 0, 0, 0) // 没有导航栏

  如果上述情况中的导航控制器又被UITabBarController管理,那么

    UIEdgeInsetsMake(64, 0, 49, 0) // 导航控制器又被UITabBarController管理

  如何取消系统的默认这自动调节功能

  ViewController.automaticallyAdjustsScrollViewInsets = NO;

  代码验证 -->

//// ViewController.m#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;@property (nonatomic, weak) UISwitch *customSwitch;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];  UISwitch *customSwitch = [[UISwitch alloc] init];  [self.scrollView addSubview:customSwitch];  self.customSwitch = customSwitch;  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{    NSLog(@"%@",self.scrollView);    NSLog(@"%@",NSStringFromUIEdgeInsets(self.scrollView.contentInset));    NSLog(@"%@",NSStringFromCGRect(self.customSwitch.bounds));  });}// 打印结果/* 情况一 只有UInavigationController <UIScrollView: 0x7fbbd301fa00; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x7fbbd27246e0>; layer = <CALayer: 0x7fbbd25176a0>; contentOffset: {0, -64}; contentSize: {0, 0}> {64, 0, 0, 0} {{0, 0}, {51, 31}} *//* 情况二 只有UInavigationController,但是隐藏了导航条 <UIScrollView: 0x7f80cb024200; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x7f80c9563330>; layer = <CALayer: 0x7f80c955f090>; contentOffset: {0, -20}; contentSize: {0, 0}> {20, 0, 0, 0} {{0, 0}, {51, 31}} *//*  情况三 既有UInavigationController,又有UITabBarController <UIScrollView: 0x7fe60903fa00; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x7fe608e3b100>; layer = <CALayer: 0x7fe608f06320>; contentOffset: {0, -64}; contentSize: {0, 0}> {64, 0, 49, 0} {{0, 0}, {51, 31}} */// 上面采用了延迟的方法(GCD中的方法)来打印,在viewDidLoad方法中打印的结果不是最终的结果,当然也可以采用下面的方法来打印- (void)viewDidLayoutSubviews {//  NSLog(@"%@",self.scrollView);//  NSLog(@"%@",NSStringFromUIEdgeInsets(self.scrollView.contentInset));  }- (void)viewDidAppear:(BOOL)animated {  //  NSLog(@"%@",self.scrollView);//  NSLog(@"%@",NSStringFromUIEdgeInsets(self.scrollView.contentInset));  }@end