在 Apples MultipleDetailViews 示例中加载已初始化的 DetailViewControllers

Question

Apple 在其 iOS 开发网站上提供了一个有关如何使用具有不同详细视图的 splitview 的示例（请参阅 MultipleDetailViews 示例）。在 RootViewController 中，每次单元格被选中时，都会初始化一个新的 DetailViewController：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

/*
 Create and configure a new detail view controller appropriate for the selection.
 */
NSUInteger row = indexPath.row;

UIViewController <SubstitutableDetailViewController> *detailViewController = nil;

if (row == 0) {
    FirstDetailViewController *newDetailViewController = [[FirstDetailViewController alloc] initWithNibName:@"FirstDetailView" bundle:nil];
    detailViewController = newDetailViewController;
}

if (row == 1) {
    SecondDetailViewController *newDetailViewController = [[SecondDetailViewController alloc] initWithNibName:@"SecondDetailView" bundle:nil];
    detailViewController = newDetailViewController;
}

// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, detailViewController, nil];
splitViewController.viewControllers = viewControllers;
[viewControllers release];

// Dismiss the popover if it's present.
if (popoverController != nil) {
    [popoverController dismissPopoverAnimated:YES];
}

// Configure the new view controller's popover button (after the view has been displayed and its toolbar/navigation bar has been created).
if (rootPopoverButtonItem != nil) {
    [detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];
}

[detailViewController release];
}

现在我的想法是，不必每次都初始化视图控制器，只需在 viewDidLoad （以及标题）中初始化控制器，并在单元格被选中时传递它们的引用：

rootviewcontroller 中 viewDidLoad 的一部分：

firstDetailViewController = [[FirstDetailViewController alloc] initWithNibName:@"FirstDetailView" bundle:nil];
secondDetailViewController = [[FirstDetailViewController alloc] initWithNibName:@"FirstDetailView" bundle:nil];

现在 tableView didselectrow 方法如下所示：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

/*
 Create and configure a new detail view controller appropriate for the selection.
 */
NSUInteger row = indexPath.row;

UIViewController <SubstitutableDetailViewController> *detailViewController = nil;

if (row == 0) {
    detailViewController = firstDetailViewController;
}

if (row == 1) {
    detailViewController = secondDetailViewController;
}

// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, detailViewController, nil];
splitViewController.viewControllers = viewControllers;
[viewControllers release];

// Dismiss the popover if it's present.
if (popoverController != nil) {
    [popoverController dismissPopoverAnimated:YES];
}

// Configure the new view controller's popover button (after the view has been displayed and its toolbar/navigation bar has been created).
if (rootPopoverButtonItem != nil) {
    [detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];
}

//[detailViewController release];
}

在横向模式下一切正常，但在纵向模式下，从第一个detailviewcontroller，到第二个，然后到第一个，然后想切换到第二个。出现以下消息：由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“无法从没有窗口的视图中呈现弹出窗口。”

从昨天晚上开始，我就试图解决这个问题，但没有找到解决方案。有人有想法吗？

干杯，多米尼克

Answer 1

我有类似的问题，但我发现这个 post 演示了在设置 splitView 的视图控制器之前必须从先前的DetailView 中删除 leftBarButtonItem 的想法。这段代码为我解决了这个问题。

这是 TPoschel 编写的代码。

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

// Retrieve the new detail view controller
UIViewController *detailViewController = [[self.allData objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];

// Add the detail view controller to a navigation controller and set the bar style
UINavigationController *detailNavigationController = [[UINavigationController alloc] initWithRootViewController:detailViewController];
detailNavigationController.navigationBar.barStyle = [[NSUserDefaults standardUserDefaults] integerForKey:@"UIBarStyle"];

// Retrieve previous detail view controller and remove the leftBarButtonItem
UINavigationController *previousDetailNavigationController = [splitViewController.viewControllers objectAtIndex:1];
UIViewController *previousDetailViewController = [[previousDetailNavigationController viewControllers] lastObject];
previousDetailViewController.navigationItem.leftBarButtonItem = nil;

// Update the split view controller's view controllers array.
NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, detailNavigationController, nil];
splitViewController.viewControllers = viewControllers;

[detailNavigationController release];
[viewControllers release];

// Dismiss the popover if it's present.
if (popoverController != nil) {
    [popoverController dismissPopoverAnimated:YES];
}

// This sets the left bar to nil when in landscape and equal to "Menu" when in portrait.
// We need to remove rootPopoverButtonItem from the previous viewController...
detailViewController.navigationItem.leftBarButtonItem = rootPopoverButtonItem;

}