检查 UIViewController 是否已经创建 [英] Check to see if UIViewController has already been created

问题描述

我正在尝试检查是否已经创建了一个视图控制器.如果视图已经存在，那么它应该成为当前视图.如果它不存在，则应该创建它并使其可见.

I'm trying to check if a viewcontroller has already been created. If the view already exists then it should become the current view. If it doesn't exist then it should be created and made visible.

我的代码是

            DemoViewController *demoController = [DemoViewController alloc];
        for(DemoViewController *view in self.navigationController.viewControllers)
        {
            if([view isKindOfClass:[DemoViewController class]])
            {
                viewExists=true;
                demoController=view;
            }

        }
        if (!viewExists) {
            demoController initWithNibName:@"DemoViewController" bundle:nil;
        }
        [view release];
        [demoController release];

我不确定我哪里出错了，但似乎没有执行 for 循环.任何帮助都会很棒！

I'm not sure where I'm going wrong but it would appear that the for loop isn't being executed. Any help would be great!

推荐答案

试试这个:

DemoViewController* demoController = nil;
for(int vv=0; vv<[self.navigationController.viewControllers count]; ++vv) {
    NSObject *vc = [self.navigationController.viewControllers objectAtIndex:vv];
    if([vc isKindOfClass:[DemoViewController class]]) {
        demoController = (DemoViewController*)vc;
    }
}

if (demoController == nil) {
    demoController = [[DemoViewController alloc] initWithNibName:@"DemoViewController" bundle:nil];
    // Do we need to push it into navigation controller?
}

[demoController release];

这篇关于检查 UIViewController 是否已经创建的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！