我正在尝试实现一个简单的 UISplitViewController，其中在纵向模式下主视图被隐藏并在弹出窗口中显示一个按钮。
我的 AppDelegate 是这样设置的：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after app launch.
self.splitViewController =[[UISplitViewController alloc]init];
self.rootViewController=[[RootViewController alloc]init];
self.detailViewController=[[FirstDetailViewController alloc]init];
UINavigationController *rootNav=[[UINavigationController alloc]initWithRootViewController:rootViewController];
UINavigationController *detailNav=[[UINavigationController alloc]initWithRootViewController:detailViewController];
self.splitViewController.viewControllers=[NSArray arrayWithObjects:rootNav,detailNav,nil];
self.splitViewController.delegate=self.detailViewController;
splitViewController.presentsWithGesture = NO;
// Add the split view controller's view to the window and display.
[self.window setRootViewController:self.splitViewController];
[window makeKeyAndVisible];
return YES;
}
在 FirstDetailViewController 我设置了一个这样的按钮：
UIImage *buttonImage = [UIImage imageNamed:@"button-menu.png"];
UIButton *aButton = [UIButton buttonWithType:UIButtonTypeCustom];
[aButton setImage:buttonImage forState:UIControlStateNormal];
aButton.frame = CGRectMake(0.0, 0.0, buttonImage.size.width, buttonImage.size.height);
[aButton addTarget:self action:@selector(showNavigation) forControlEvents:UIControlEventTouchUpInside];
aBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:aButton];
self.appDelegate.rootPopoverButtonItem = aBarButtonItem;
showNavigation 看起来像这样：
-(void)showNavigation{
NSLog(@"I am in show navigation and pc=%@",self.popoverController);
[self.popoverController presentPopoverFromRect:self.view.frame
inView:self.view
permittedArrowDirections:UIPopoverArrowDirectionAny
animated:YES];
}
当我最初加载应用程序并按下按钮时，我得到一个 NSLog
I am in show navigation and pc=(null)
并且弹出窗口没有显示。现在，当我将设备旋转到横向模式，然后返回纵向时，主视图会按预期隐藏和显示，并且按钮现在可以在纵向模式下工作。
这是处理旋转的代码：
- (void)splitViewController: (UISplitViewController*)svc willHideViewController:(UIViewController *)aViewController withBarButtonItem:(UIBarButtonItem*)barButtonItem forPopoverController: (UIPopoverController*)pc {
[[self navigationItem] setLeftBarButtonItem:aBarButtonItem];
[self setPopoverController:pc];
self.appDelegate.rootPopoverButtonItem = aBarButtonItem;
}
// Called when the view is shown again in the split view, invalidating the button and popover controller.
- (void)splitViewController: (UISplitViewController*)svc willShowViewController:(UIViewController *)aViewController invalidatingBarButtonItem:(UIBarButtonItem *)barButtonItem {
[[self navigationItem] setLeftBarButtonItem:nil];
[self setPopoverController:nil];
self.appDelegate.rootPopoverButtonItem = aBarButtonItem;
}
如何在任何旋转发生之前让 popovercontroller 不为空？