UISplitView，在设置委托时接收语义问题

Question

我一直关注Big Nerd Ranch的iOS编程指南（第3版）来设置我的Xcode项目，该项目显示了我公司产品的列表，然后是每个产品的详细视图。

我让应用程序以我需要的方式游泳，但是当我试图想象用户体验时，我开始遇到麻烦。添加一个适用于iPad的UISplitViewController让我无法忍受头疼和下午的浪费。

目前，我在代理相关代码上报告了语义问题。一个在DetailViewController.h中，另一个在ListViewController.m中。

我会在发布之前总结一下我对此代码的意图，但由于我的经验不足，我可能会遗漏一些细微之处：

AppDelegate分配UITableViewController（ListViewController类）和UIViewController（DetailViewController类），然后检查iPad。如果是iPad，它会使用两个视图的数组创建一个UISplitViewController。否则，它将ListViewController加载为主视图。

在我尝试在两个视图之间创建委托关系之前，应用程序正在成功构建，但iPad UISplitViewController仅加载了一个空的详细信息视图。 iphone加载了ListViewController，然后选择一行显示一个空的详细信息视图（DetailViewController）。当您返回到TableView，并选择相同或另一个表格单元格时，正确的信息将加载到DetailView中。这让我相信TableView的初始实例没有正确传递选择，但返回它（重新分配它？）将纠正问题。我希望代理设置能解决这个问题。由于我不能使那部分工作，我无法测试这个理论。我想我会提到它。

关于UISplitViewController的问题和教程，我已经尽可能多地了解了（正确的关键词和搜索词不适合我），但它们与我在项目中已经设置的内容有很大不同，无论是应用程序的行为还是代码的整体结构。当我看起来如此接近时，我宁愿不必重新开始。

我打开了BigNerdRanch示例代码（确实有效），正如我所说，唯一的区别似乎与我想要显示信息的方式有关。在这一点上，我需要一些帮助，请找出我做错了什么。

提前致谢！

AppDelegate.m：

#import "ProductFeedAppDelegate.h"
#import "ListViewController.h"
#import "DetailViewController.h"

@implementation ProductFeedAppDelegate

@synthesize window = _window;
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    ListViewController *lvc = [[ListViewController alloc] initWithStyle:UITableViewStylePlain];
    UINavigationController *masterNav = [[UINavigationController alloc] initWithRootViewController:lvc];

    DetailViewController *dvc = [[DetailViewController alloc] init];
    [lvc setDetailViewController:dvc];

    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {


        UINavigationController *detailNav = [[UINavigationController alloc] initWithRootViewController:dvc];
        NSArray *vcs = [NSArray arrayWithObjects:masterNav, detailNav, nil];
        UISplitViewController *svc = [[UISplitViewController alloc] init];

        //set delegate
        [svc setDelegate:dvc];
        [svc setViewControllers:vcs];

        [[self window] setRootViewController:svc];

    } else {

        [[self window] setRootViewController:masterNav];

    }



    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

//... trimmed out some template code to spare you
@end

` ListViewController.h：

    #import <Foundation/Foundation.h>
#import "ProductItemCell.h"
//#import "ItemStore.h"
#import "DetailViewController.h"

@class DetailViewController;

@class RSSChannel;

@interface ListViewController : UITableViewController 
{

    RSSChannel *channel;
}

@property (nonatomic, strong) DetailViewController *detailViewController;

-(void)fetchEntries;

@end

//A new protocol named ListViewControllerDelegate
@protocol ListViewControllerDelegate

//Classes that conform to this protocol must implement this method:
- (void)listViewController:(ListViewController *)lvc handleObject:(id)object;
@end

ListViewController.m：

#import "ListViewController.h"
#import "RSSChannel.h"
#import "RSSItem.h"
#import "DetailViewController.h"
#import "ContactViewController.h"
#import "FeedStore.h"

@implementation ListViewController
@synthesize detailViewController;

- (void)transferBarButtonToViewController:(UIViewController *)vc
{
    // Trimming Code
}
- (id)initWithStyle:(UITableViewStyle)style
{
    // Trimming Code
}

- (void)showInfo:(id)sender
{
    // Create the contact view controller
    ContactViewController *contactViewController = [[ContactViewController alloc] init];

    if ([self splitViewController]) {
        [self transferBarButtonToViewController:contactViewController];

        UINavigationController *nvc = [[UINavigationController alloc]
                                       initWithRootViewController:contactViewController];

        // Create an array with our nav controller and this new VC's nav controller
        NSArray *vcs = [NSArray arrayWithObjects:[self navigationController],
                        nvc,
                        nil];

        // Grab a pointer to the split view controller
        // and reset its view controllers array.
        [[self splitViewController] setViewControllers:vcs];

        // Make contact view controller the delegate of the split view controller
        [[self splitViewController] setDelegate:contactViewController];

        // If a row has been selected, deselect it so that a row
        // is not selected when viewing the info
        NSIndexPath *selectedRow = [[self tableView] indexPathForSelectedRow];
        if (selectedRow)
            [[self tableView] deselectRowAtIndexPath:selectedRow animated:YES];
    } else {
        [[self navigationController] pushViewController:contactViewController
                                               animated:YES];
    }

    // Give the VC the channel object through the protocol message
   // [channelViewController listViewController:self handleObject:channel];
}


- (void)viewDidLoad
{
    // Trimming Code
}


- (NSInteger)tableView:(UITableView *)tableView
 numberOfRowsInSection:(NSInteger)section
{
    return [[channel items] count];
}

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

    // Trimming Code

}

- (void)fetchEntries
{
    // Trimming Code
}

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

    if (![self splitViewController])
        [[self navigationController] pushViewController:detailViewController animated:YES];
    else {
        [self transferBarButtonToViewController:detailViewController];
        // We have to create a new navigation controller, as the old one
        // was only retained by the split view controller and is now gone
        UINavigationController *nav =
        [[UINavigationController alloc] initWithRootViewController:detailViewController];

        NSArray *vcs = [NSArray arrayWithObjects:[self navigationController],
                        nav,
                        nil];

        [[self splitViewController] setViewControllers:vcs];

        // Make the detail view controller the delegate of the split view controller
        [[self splitViewController] setDelegate:detailViewController];

    }

    RSSItem *item = [[channel items] objectAtIndex:[indexPath row]];

     // Next line reports: No visible @interface for 'DetailViewController' declares the selector 'listViewController:handleObject:'
    [detailViewController listViewController:self handleObject:item]; 



}


@end

DetailViewController.h：

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import "ListViewController.h"

@class RSSItem;
@class Reachability;

@interface DetailViewController : UIViewController <ListViewControllerDelegate> // Cannot find protocol declaration for 'ListViewControllerDelegate' 
{
    __weak IBOutlet UILabel *nameField;
    __weak IBOutlet UITextView *descriptField;
    __weak IBOutlet UIImageView *imageView;
    __weak IBOutlet UITextView *introtextField;
    __weak IBOutlet UIButton *dsButton;
    __weak IBOutlet UIButton *aeButton;
    __weak IBOutlet UIButton *imButton;
}

-(BOOL)reachable;

@property (nonatomic, strong) RSSItem *item;
@property (nonatomic, strong) UIImage *productImage;

@end

DetailViewController.m：

#import "DetailViewController.h"
#import "RSSItem.h"
#import "RSSChannel.h"
#import "Reachability.h"


@interface DetailViewController ()

@end

@implementation DetailViewController

- (void)listViewController:(ListViewController *)lvc handleObject:(id)object
{
    //RSSItem *item = object; //This was in the example code but if left in the next line reported "Local declaration of 'item' hides instance variable"
    // Validate the RSSItem
    if (![item isKindOfClass:[RSSItem class]])
          return;

    [self setItem:item];
    [[self navigationItem] setTitle:[item name]];


    [nameField setText:[item name]];
    [descriptField setText:[item descript]];
    [introtextField setText:[item introtext]];
}

@synthesize item;

- (BOOL)reachable{
    // Trimming Code
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    [[self view] setBackgroundColor:[UIColor whiteColor]];
}

- (void)viewWillAppear:(BOOL)animated
{
    if (item){
        [super viewWillAppear:animated];

        [nameField setText:[item name]];
        [descriptField setText:[item descript]];
        [introtextField setText:[item introtext]];
        // Trimming Code (all the stuff that looks for this or that value and acts upon it)
    }  else {
        // The following appears in the log:
        NSLog(@"There's no item selected");
    }

}



@end

Answer 1

我认为你遇到了一个问题，编译器因为有几个

而感到困惑

#import "DetailViewController.h"

如果从ListViewController.h中删除此导入并保留

  

@class DetailViewController;

然后我认为这将摆脱你的编译器问题。

您可能需要将< UISplitViewControllerDelegate >添加到其他几个类中。看起来您在拆分视图中将它们设置为委托但未采用协议。

Answer 2

委托关系未正确设置100％。以下是修复方法。

在ListViewController.m中，添加了一个类扩展名：

@interface ListViewController() <UISplitViewControllerDelegate>
@end

在ListViewController.h中，删除了：

#import "DetailViewController.h"

在DetailViewController.h中，将行更改为：

@interface DetailViewController : UIViewController <ListViewControllerDelegate, UISplitViewControllerDelegate>

在ContactViewController.h中，将行更改为：

@interface ContactViewController : UIViewController <MFMailComposeViewControllerDelegate, UISplitViewControllerDelegate>

这些事情清除了所有错误。这不是，正如我在原始帖子中所希望的那样，纠正了我的项目没有被传递给detailViewController的问题，因为该问题是在DetailViewController.m的handleObject语句中使用“item”而不是“object”的结果。