更改视图会让我尝试在视图不在窗口层次结构中的vc上显示vc1

我已经创建了一个测试应用程序来了解视图/视图控制器如何工作以及如何在没有故事板或笔尖的情况下以编程方式在它们之间进行导航 .

我基本上设置了 rootViewController ，称为Viewcontroller，它在_1593189中设置 .

此视图在启动时显示view1，其中包含一个uibutton，它在 rootViewController 中调用通知以显示view2 . 但是，当我这样做时，我不断收到警告：

Warning: Attempt to present <View1: 0x7be66c80> on <ViewController: 0x7be62980> whose view is not in the window hierarchy!

我控制viewcontroller的代码如下：

#import "ViewController.h"
    #import "View1.h"
    #import "View2.h"
    @interface ViewController ()

    @end

    @implementation ViewController
    -(void) loadView{
        [super loadView];
    }
    -(void)viewDidAppear:(BOOL)animated{
        NSLog(@"View appeared");
        [[NSNotificationCenter defaultCenter] removeObserver:self name:@"view1" object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(view1:) name:@"view1" object:nil];
        [[NSNotificationCenter defaultCenter] removeObserver:self name:@"view2" object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(view2:) name:@"view2" object:nil];
        [self showView1];
    }
    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }
    -(void)view1:(NSNotification*) notification{
        NSLog(@"Showing view1");
        [self dismissViewControllerAnimated:YES completion:nil];
        [self showView1];
    }
    -(void)showView1{
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.view.window.rootViewController presentViewController:[[View1 alloc]init] animated:YES completion:nil];
        });
    }
    -(void)view2:(NSNotification*) notification{
        NSLog(@"Showing view2");
        [self dismissViewControllerAnimated:YES completion:nil];
        [self showView2];
    }
    -(void)showView2{
        dispatch_async(dispatch_get_main_queue(), ^{
            [self presentViewController:[[View1 alloc]init] animated:YES completion:nil];
        });
    }

@end

编辑：我忘了提到view1最初显示没有任何错误或问题 .

编辑：view1和view2的代码完全相同，只是它们发送不同的通知：

#import "View1.h"

    @interface View1 ()

    @end

    @implementation View1

    - (void)loadView {
        [super loadView];
        self.view.frame = [[UIApplication sharedApplication].keyWindow bounds];
        // Do view setup here.
        UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        [button addTarget:self
                   action:@selector(touchedLogin:)
         forControlEvents:UIControlEventTouchUpInside];
        [button setTitle:@"Login" forState:UIControlStateNormal];

        button.layer.cornerRadius=1;
        button.frame = CGRectMake(self.view.bounds.size.width/2-100, self.view.bounds.size.height-200, 200, 60.0);
        [button setTitleEdgeInsets:UIEdgeInsetsMake(5.0, 0.0, 0.0, 0.0)];

        //[_window setBackgroundColor:[UIColor whiteColor]];
        [self.view addSubview:button];
    }
    -(void)touchedLogin:(id*)sender{
        [[NSNotificationCenter defaultCenter] postNotificationName:@"view2" object:nil];
    }

    @end