iphone - 我有一个 iPad 应用程序，由于未捕获的异常 'NSInternalInconsistencyException'，不断出现终止应用程序的情况

Question

第一个按钮显示总统列表，当您单击他们时，您会看到他们的维基百科页面。一切都很顺利，直到我添加了另一个按钮，可以让您将页面语言从英语更改为德语等。我在调试器中不断收到此错误:

-[UITableView _createPreparedCellForGlobalRow:withIndexPath:]、/SourceCache/UIKit_Sim/UIKit-1914.84/UITableView.m:6061 中断言失败2012-04-30 17:30:01.293 Presidents[11151:f803] * 由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因:“UITableView dataSource 必须从 tableView:cellForRowAtIndexPath: 返回一个单元格”*第一次抛出调用堆栈:

我正在阅读一本教程，我认为他们再次缺少代码。任何想法都会很棒!

编辑:菜鸟移动我的家伙，我粘贴了错误的代码部分:这个新部分是我在 BIDMasterViewController 之后添加的自定义弹出窗口，工作正常。这个新部分就是问题出现的地方:

   #import "BIDLanguageListController.h"
#import "BIDDetailViewController.h"

@interface BIDLanguageListController ()

@end

@implementation BIDLanguageListController

@synthesize languageNames;
@synthesize languageCodes;
@synthesize detailViewController;

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.languageNames = [NSArray arrayWithObjects:@"English", @"French",
                          @"German", @"Spanish", nil];
    self.languageCodes = [NSArray arrayWithObjects:@"en", @"fr", @"de", @"es", nil];
    self.clearsSelectionOnViewWillAppear = NO;
    self.contentSizeForViewInPopover = CGSizeMake(320.0, [self.languageCodes count] * 44.0);

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

- (void)viewDidUnload
{
    [super viewDidUnload];

    self.detailViewController = nil;
    self.languageNames = nil;
    self.languageCodes = nil;
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

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

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{

    // Return the number of sections.
    return 1;
}

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

    // Return the number of rows in the section.
    return [self.languageCodes count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    // Configure the cell...
    cell.textLabel.text = [languageNames objectAtIndex:[indexPath row]];

    return cell;
}

/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}
*/

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}
*/

/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
   detailViewController.languageString = [self.languageCodes objectAtIndex:
                                          [indexPath row]];
}

@end

Answer 1

您从未真正实例化单元!网络上有很多关于如何重用 UITableViewCells 的优秀文档。

Apple 的 TableView 编程指南非常棒，绝对是必读的: http://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/TableView_iPhone/TableViewCells/TableViewCells.html#//apple_ref/doc/uid/TP40007451-CH7-SW1

同时，为了快速解决问题，请将您的方法更改为:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    //THIS IS THE IMPORTANT PART YOU ARE MISSING
    if(cell == nil) {
        //AND IF YOU PUT AN NSLOG IN HERE, YOU'LL SEE THIS IS CALLED ABOUT THE
        //NUMBER OF TIMES FOR THE INITIALLY VISIBLE CELLS ON THE SCREEN, PLUS 1 OR 2
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    }

    // Configure the cell...
    cell.textLabel.text = [languageNames objectAtIndex:[indexPath row]];

    return cell;
}