background color disappeared

SecondViewController.h

#import <UIKit/UIKit.h>

@interface SecondViewController : UIViewController

@end

SecondViewController.m

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor grayColor];
    
    UILabel * testLabel = [[UILabel alloc] initWithFrame:CGRectMake(100, 100, 200, 300)];
    testLabel.center = self.view.center;
    testLabel.text = @"Second";
    testLabel.textAlignment = NSTextAlignmentCenter;
    testLabel.backgroundColor = [UIColor orangeColor];
    [self.view addSubview:testLabel];
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, UINavigationControllerDelegate>

@end

ViewController.m

#import "ViewController.h"
#import "SecondViewController.h"

#import "AMWaveTransition.h"

@interface ViewController ()

@property (copy, nonatomic) NSArray * data;
@property (strong, nonatomic) UITableView * tableView;

@end

@implementation ViewController

@synthesize data, tableView;

- (void)viewDidLoad {
    [super viewDidLoad];
    
    data = @[@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J",];
    
    tableView = [[UITableView alloc] initWithFrame:self.view.bounds style:UITableViewStylePlain];
    tableView.delegate = self;
    tableView.dataSource = self;
    [self.view addSubview:tableView];
    
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [data count];
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString * cellIdentifier = @"CellIdentifier";
    UITableViewCell * cell = [self.tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (!cell) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
        cell.textLabel.text = data[indexPath.row];
    }
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    SecondViewController * secondVC = [[SecondViewController alloc] init];
    [self.navigationController pushViewController:secondVC animated:YES];
}

#pragma mark - AMWaveTransition Methods

- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                  animationControllerForOperation:(UINavigationControllerOperation)operation
                                               fromViewController:(UIViewController*)fromVC
                                                 toViewController:(UIViewController*)toVC
{
    if (operation != UINavigationControllerOperationNone) {
        // Return your preferred transition operation
        return [AMWaveTransition transitionWithOperation:operation];
    }
    return nil;
}

- (NSArray*)visibleCells
{
    return [self.tableView visibleCells];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [self.navigationController setDelegate:self];
}

- (void)dealloc
{
    [self.navigationController setDelegate:nil];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end