UIViewController 可能不响应 showRootPopoverButtonItem

Posted 2023-03-13

【中文标题】UIViewController 可能不响应 showRootPopoverButtonItem

【英文标题】：UIViewController may not respond to showRootPopoverButtonItem

【发布时间】：2012-02-08 21:47:48

【问题描述】：

我正在使用 Apple 的 MuiltipleDetailViewController 示例应用程序并收到消息“UIViewController 可能无法响应 showRootPopoverButtonItem”

这在 XCode 3.X 中有效，但我收到了 4.2 的消息

应用程序本身功能 100%，每个笔尖都能识别弹出框，横向模式下左侧的表格也是如此。但我不能提交这个警告。我需要改变什么？

RootViewController.h

#import <UIKit/UIKit.h>


/*
 SubstitutableDetailViewController defines the protocol that detail view controllers must adopt. The protocol specifies methods to hide and show the bar button item controlling the popover.

 */
@protocol SubstitutableDetailViewController <NSObject>
- (void)showRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem;
- (void)invalidateRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem;
@end


@interface RootViewController : UITableViewController <UISplitViewControllerDelegate> 

    UISplitViewController *splitViewController;

    UIPopoverController *popoverController;    
    UIBarButtonItem *rootPopoverButtonItem;

    //UINavigationBar *navigationBar;


@property (nonatomic, assign) IBOutlet UISplitViewController *splitViewController;

@property (nonatomic, retain) UIPopoverController *popoverController;
@property (nonatomic, retain) UIBarButtonItem *rootPopoverButtonItem;


//@property (nonatomic, retain) IBOutlet UINavigationBar *navigationBar;

@end

RootViewController.m：

#import "RootViewController.h"
#import "WebViewController.h"
#import "Twitter.h"
//#import "SubstitutableDetailViewController.h"



@implementation RootViewController

@synthesize splitViewController, popoverController, rootPopoverButtonItem;//, navigationBar;


#pragma mark -
#pragma mark View lifecycle

- (void)viewDidLoad 

    [super viewDidLoad];
    // Set the content size for the popover: there are just two rows in the table view, so set to rowHeight*2.
    self.contentSizeForViewInPopover = CGSizeMake(310.0, self.tableView.rowHeight*2.0);
    //self.navigationController.navigationBar.tintColor = [UIColor colorWithRed:255/255 green:104/255 blue:1/255 alpha:1];

/*
-(void)customizeAppearance 
    //create resizable images
    UIImage *bluImage = [UIImage imageNamed:@"blu.jpg"];// resizableImageWithCapInsets:(0, 0, 0, 0)];

    //set the bg for *all* UINavBars
    [[UINavigationBar appearance] setBackgroundImage:bluImage forBarMetrics:UIBarMetricsDefault];

 */

-(void) viewDidUnload 
    [super viewDidUnload];

    self.splitViewController = nil;
    self.rootPopoverButtonItem = nil;


- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation 
    return YES;



- (void)splitViewController:(UISplitViewController*)svc willHideViewController:(UIViewController *)aViewController withBarButtonItem:(UIBarButtonItem*)barButtonItem 
       forPopoverController:(UIPopoverController*)pc 

    // Keep references to the popover controller and the popover button, and tell the detail view controller to show the button.
    barButtonItem.title = @"Index";
    self.popoverController = pc;
    self.rootPopoverButtonItem = barButtonItem;
    UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
    [detailViewController showRootPopoverButtonItem:rootPopoverButtonItem];



- (void)splitViewController:(UISplitViewController*)svc willShowViewController:(UIViewController *)aViewController 
  invalidatingBarButtonItem:(UIBarButtonItem *)barButtonItem 

    // Nil out references to the popover controller and the popover button, and tell the detail view controller to hide the button.
    UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
    [detailViewController invalidateRootPopoverButtonItem:rootPopoverButtonItem];
    self.popoverController = nil;
    self.rootPopoverButtonItem = nil;



#pragma mark -
#pragma mark Table view data source

- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section 

    // Two sections, one for each detail view controller.
    return 2;



- (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 

    static NSString *CellIdentifier = @"RootViewControllerCellIdentifier";

    // Dequeue or create a cell of the appropriate type.
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) 
        //cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    

    // Set appropriate labels for the cells.
    if (indexPath.row == 0) 
        cell.textLabel.text = @"Twitter";
    

    else if (indexPath.row == 1) 
        cell.textLabel.text = @"Contact Us";
    


    cell.textLabel.textColor = [UIColor whiteColor];
    cell.textLabel.backgroundColor = [UIColor blackColor];
    cell.contentView.backgroundColor = [UIColor blackColor];
    cell.detailTextLabel.backgroundColor = [UIColor blackColor];
    return cell;



#pragma mark -
#pragma mark Table view selection

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

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

    UIViewController *detailViewController = nil;

    if (row == 0) 
        Twitter *newDetailViewController = [[Twitter alloc] 
                                                      initWithNibName:@"Twitter" 
                                                      bundle:nil];
        detailViewController = newDetailViewController;
        

    if (row == 1) 
        WebViewController *newDetailViewController = [[WebViewController alloc] 
                                                      initWithNibName:@"WebViewController" 
                                                      bundle:nil];
        newDetailViewController.detailURL=
        [[NSURL alloc] initWithString:@"http://www.chipmunkmobile.com/contact.html"];

        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];


#pragma mark -
#pragma mark Managing the popover


/*
- (void)showRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem 
    // Add the popover button to the left navigation item.
    [navigationBar.topItem setLeftBarButtonItem:barButtonItem animated:NO];



- (void)invalidateRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem 
    // Remove the popover button.
    [navigationBar.topItem setLeftBarButtonItem:nil animated:NO];

 */

#pragma mark -
#pragma mark Memory management

- (void)dealloc 
    [popoverController release];
    [rootPopoverButtonItem release];
    [super dealloc];


@end

这是我收到警告的确切行的图像

【问题讨论】：

你已经把那个方法注释掉了......你期望发生什么？

【参考方案1】：

您收到此警告的原因是因为UIViewController *detailViewController UIViewController 没有名为“showRootPopoverButtonItem”的方法。如果您想摆脱警告，只需这样做：

[(WebViewController*)detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];

或

[(Twitter*)detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];

你只需要让它知道它不仅仅是一个 viewController，它是你创建的一个子类 viewController。所以无论什么类 showRootPopoverButtonItem: 你只需要类型转换它。

【参考方案2】：

如果您想保持代码完全相同但摆脱警告，您可以这样做。

    if (rootPopoverButtonItem != nil) 
        [detailViewController performSelector:@selector(showRootPopoverButtonItem:) withObject:self.rootPopoverButtonItem];
    

如果你想更加小心，你应该使用这个。

 if (rootPopoverButtonItem != nil && [detailViewController respondsToSelector:@selector(showRootPopoverButtonItem:)]) 
        [detailViewController performSelector:@selector(showRootPopoverButtonItem:) withObject:self.rootPopoverButtonItem];
    

更新

阅读完您的代码后，您可以像在其他函数中一样在 detailViewController 上指定委托。

UIViewController<SubstitutableDetailViewController> *detailViewController = nil;

    if (row == 0) 
    //...

【参考方案3】：

(1)指定详细ViewController的类型：[(TYPE *)OBJECTNAME...(2)然后指定方法调用[(TYPE *)OBJECTNAME METHODCALL];

(*) 您收到警告是因为编译器不知道您正在使用什么类型的对象。如果你继承了 UIViewController，那么你必须在访问方法时指定类型。确保方法在 .h 中，以便你可以访问它。