从另一个视图控制器错误以编程方式启动 Web 视图

Question

这是我的主要视图控制器：

#import "ViewController.h"
#import "WebViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    WebViewController *wvc = [[WebViewController alloc]init];
    [self presentViewController:wvc animated:NO completion:nil];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

这是网络视图控制器：

#import "WebViewController.h"
@interface WebViewController ()
@end
@implementation WebViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    UIWebView *webview=[[UIWebView alloc]initWithFrame:CGRectMake(0, 0, 1024,768)];
    NSString *url=@"https://www.google.com";
    NSURL *nsurl=[NSURL URLWithString:url];
    NSURLRequest *nsrequest=[NSURLRequest requestWithURL:nsurl];
    [webview loadRequest:nsrequest];
    [self.view addSubview:webview];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

谷歌页面没有加载，我得到的警告是

警告：尝试在 其视图不在窗口中 等级制度！

这

到底是怎么回事？

Answer 1

我建议仔细检查。按照您的代码，我刚刚确认了这一点：

#import "LoadPresentViewController.h"
#import "WebViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (IBAction)doLoadPresent:(id)sender {
    WebViewController *wvc = [[WebViewController alloc]init];
    [self presentViewController:wvc animated:NO completion:nil];
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // this fails in viewDidLoad
//  WebViewController *wvc = [[WebViewController alloc]init];
//  [self presentViewController:wvc animated:NO completion:nil];
}
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    // this succeeds in viewDidAppear
    WebViewController *wvc = [[WebViewController alloc]init];
    [self presentViewController:wvc animated:NO completion:nil];
}
@end