UITableViewController* tvc=[[UITableViewController alloc] initWithStyle:UITableViewStylePlain];
[self addChildViewController:tvc];

_tableView = tvc.tableView;
_tableView.frame=self.view.bounds;

_tableView.dataSource =self;

_tableView.delegate = self;


[self.view addSubview:_tableView];

在 iOS12 以后这个不起作用
可以改成

• (void)viewDidLoad {
  [super viewDidLoad];
  [[NSNotificationCenter defaultCenter]addObserver:self
  selector:@selector(keyboardWillShow:)
  name:UIKeyboardWillShowNotification
  object:nil];
  [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification
  object:nil];
  }

-(void)keyboardWillShow:(NSNotification*)note
{
if ([[[UIDevice currentDevice] systemVersion] floatValue]>=12.0) {
CGRect keyBoardRect=[note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
_tableView.contentInset = UIEdgeInsetsMake(0,0,keyBoardRect.size.height-35,0);
}

}

pragma mark 键盘消失

-(void)keyboardWillHide:(NSNotification*)note
{
if ([[[UIDevice currentDevice] systemVersion] floatValue]>=12.0) {
_tableView.contentInset = UIEdgeInsetsZero;
}

}