UIAlertView and UIWindow in AppDelegat.m succession

AppDelegate.m

//
//  ViewController.m
//  TestAlert
//
//  Created by akira on 6/10/14.
//  Copyright (c) 2014 akira. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"title" message:@"message" delegate:nil cancelButtonTitle:@"NG" otherButtonTitles:@"OK", nil ];
    [alert show];
    
    NSLog(@"viewDidLoad ------------------------------------------------");
    NSLog(@"keyWindow: %@", [UIApplication sharedApplication].keyWindow);
    NSLog(@"windows : %@", [UIApplication sharedApplication].keyWindow);
    
}

- (void)viewWillAppear:(BOOL)animated
{
    NSLog(@"viewWillApper ------------------------------------------------");
    NSLog(@"keyWindow: %@", [UIApplication sharedApplication].keyWindow);
    NSLog(@"windows : %@", [UIApplication sharedApplication].keyWindow);
}

- (void)viewDidAppear:(BOOL)animated
{
    NSLog(@"viewDidApper ------------------------------------------------");
    NSLog(@"keyWindow: %@", [UIApplication sharedApplication].keyWindow);
    NSLog(@"windows : %@", [UIApplication sharedApplication].keyWindow);
}


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

@end