typedef struct UIEdgeInsets {
CGFloat top, left, bottom, right;
} UIEdgeInsets;
////
typedef struct NSDirectionalEdgeInsets {
CGFloat top, leading, bottom, trailing; 
} NSDirectionalEdgeInsets

if ([UIView userInterfaceLayoutDirectionForSemanticContentAttribute:self.view.semanticContentAttribute] == UIUserInterfaceLayoutDirectionRightToLeft)
{
// Right to left 语言下每行尾部在左边
self.view.layoutMargins.left = 30;
}
else
{
self.view.layoutMargins.right = 30;
}

self.view.directionalLayoutMargins = NSDirectionalEdgeInsetsMake(0, 0, 0, 30);

- (void)viewDidLoad
{
[super viewDidLoad];

NSString *edgeStr = NSStringFromUIEdgeInsets(self.view.safeAreaInsets);
NSString *layoutFrmStr = NSStringFromCGRect(self.view.safeAreaLayoutGuide.layoutFrame);
NSLog(@"viewDidLoad safeAreaInsets = %@, layoutFrame = %@", edgeStr, layoutFrmStr);=
}

- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];

NSString *edgeStr = NSStringFromUIEdgeInsets(self.view.safeAreaInsets);
NSString *layoutFrmStr = NSStringFromCGRect(self.view.safeAreaLayoutGuide.layoutFrame);
NSLog(@"viewDidAppear safeAreaInsets = %@, layoutFrame = %@", edgeStr, layoutFrmStr);
}

2017-09-19 14:45:50.246095+0800 Sample[5608:1365070] viewDidLoad safeAreaInsets = {0, 0, 0, 0}, layoutFrame = {{0, 0}, {375, 667}}
2017-09-19 14:45:50.257807+0800 Sample[5608:1365070] viewDidAppear safeAreaInsets = {20, 0, 0, 0}, layoutFrame = {{0, 20}, {375, 603}}

- (void)safeAreaInsetsDidChange
{
//写入变更安全区域后的代码...
}

self.additionalSafeAreaInsets = UIEdgeInsetsMake(30, 0, 0, 30);

typedef NS_ENUM(NSInteger, UINavigationItemLargeTitleDisplayMode)
{ 
/// 自动模式，会继承前一个NavigationItem所设置的模式
UINavigationItemLargeTitleDisplayModeAutomatic,
/// 当前 Navigationitem 总是启用大标题模式
UINavigationItemLargeTitleDisplayModeAlways,
/// 当前 Navigationitem 总是禁用大标题模式
UINavigationItemLargeTitleDisplayModeNever,
}

self.navigationItem.largeTitleDisplayMode = UINavigationItemLargeTitleDisplayModeAlways;

- (void)awakeFromNib
{
[super awakeFromNib];
//设置SearchController到navigationItem
self.searchController = [[UISearchController alloc] initWithSearchResultsController:self];
self.navigationItem.searchController = self.searchController;
self.navigationItem.hidesSearchBarWhenScrolling = YES;
}

- (void)viewDidLoad
{
[super viewDidLoad];

NSLog(@"viewDidLoad");
NSLog(@"self.tableView.contentInset = %@", NSStringFromUIEdgeInsets(self.tableView.contentInset));
NSLog(@"self.tableView.adjustedContentInset = %@", NSStringFromUIEdgeInsets(self.tableView.adjustedContentInset));
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];

NSLog(@"viewDidAppear");
NSLog(@"self.tableView.contentInset = %@", NSStringFromUIEdgeInsets(self.tableView.contentInset));
NSLog(@"self.tableView.adjustedContentInset = %@", NSStringFromUIEdgeInsets(self.tableView.adjustedContentInset));
}

2017-09-20 11:54:09.361348+0800 Sample[1276:375286] viewDidLoad
2017-09-20 11:54:09.361432+0800 Sample[1276:375286] self.tableView.contentInset = {0, 0, 0, 0}
2017-09-20 11:54:09.361462+0800 Sample[1276:375286] self.tableView.adjustedContentInset = {0, 0, 0, 0}
2017-09-20 11:54:09.420000+0800 Sample[1276:375286] viewDidAppear
2017-09-20 11:54:09.420378+0800 Sample[1276:375286] self.tableView.contentInset = {0, 0, 0, 0}
2017-09-20 11:54:09.420554+0800 Sample[1276:375286] self.tableView.adjustedContentInset = {20, 0, 0, 0}

typedef NS_ENUM(NSInteger, UIScrollViewContentInsetAdjustmentBehavior) {
UIScrollViewContentInsetAdjustmentAutomatic,
UIScrollViewContentInsetAdjustmentScrollableAxes, 
UIScrollViewContentInsetAdjustmentNever,
UIScrollViewContentInsetAdjustmentAlways, 
}

//重写方法
- (void)adjustedContentInsetDidChange
{
[super adjustedContentInsetDidChange];

//执行操作...
}

//实现委托
- (void)scrollViewDidChangeAdjustedContentInset:(UIScrollView *)scrollView
{
//执行操作...
}

dispatch_async(dispatch_get_global_queue(0, 0), ^{
self.tv = [[UITableView alloc] initWithFrame:self.view.bounds];
[self.view addSubview:self.tv];
NSLog(@"self.tv.adjustedContentInset = %@", NSStringFromUIEdgeInsets(self.tv.adjustedContentInset));
});

=================================================================
Main Thread Checker: UI API called on a background thread: -[UIView bounds]
PID: 16919, TID: 2972321, Thread name: (none), Queue name: com.apple.root.default-qos, QoS: 21
Backtrace:
4 Sample    0x00000001004885dc __29-[ViewController viewDidLoad]_block_invoke + 112
5 libdispatch.dylib   0x000000010077149c _dispatch_call_block_and_release + 24
6 libdispatch.dylib   0x000000010077145c _dispatch_client_callout + 16
7 libdispatch.dylib   0x000000010077d56c _dispatch_queue_override_invoke + 980
8 libdispatch.dylib   0x0000000100782b54 _dispatch_root_queue_drain + 616
9 libdispatch.dylib   0x0000000100782880 _dispatch_worker_thread3 + 136
10 libsystem_pthread.dylib  0x000000018300b130 _pthread_wqthread + 1268
11 libsystem_pthread.dylib  0x000000018300ac30 start_wqthread + 4