解析的提要在 UITableView 上不可见，cellForRowAtIndexPath 方法未被访问
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【中文标题】解析的提要在 UITableView 上不可见，cellForRowAtIndexPath 方法未被访问【英文标题】：parsed feed not visible on UITableView, cellForRowAtIndexPath method not getting accessed 【发布时间】：2013-04-22 05:39:41 【问题描述】：我试图在表格视图上显示已解析的 Yahoo RSS 提要。但是屏幕上什么也没有显示。当我使用断点时，我开始知道控件根本不会使用 cellForRowAtIndexPath 方法。我不知道为什么会这样。 yahoo feed的结构如下：
<?xml version="1.0" encoding="utf-8"?>
<rss xmlns:media="http://search.yahoo.com/mrss/" version="2.0">
<channel>
<title>Yahoo! News - Latest News & Headlines</title>
<link>http://news.yahoo.com/</link>
<description>The latest news and headlines from Yahoo! News. Get breaking news stories and in-depth coverage with videos and photos.</description>
<language>en-US</language>
<copyright>Copyright (c) 2013 Yahoo! Inc. All rights reserved</copyright>
<pubDate>Sun, 21 Apr 2013 17:08:00 -0400</pubDate>
<ttl>5</ttl>
<image>
<title>Yahoo! News - Latest News & Headlines</title>
<link>http://news.yahoo.com/</link>
<url>http://l.yimg.com/a/i/us/nws/th/main_142c.gif</url>
</image>
<item><title>After the bombings, the blame game begins</title><description><p><a href="http://news.yahoo.com/boston-marathon-bombing-blame-game-begins-210800101.html"><img src="http://l3.yimg.com/bt/api/res/1.2/uiv31afw5K_BzPxeYQz44Q--/YXBwaWQ9eW5ld3M7Zmk9ZmlsbDtoPTg2O3E9ODU7dz0xMzA-/http://media.zenfs.com/en_us/News/Reuters/2013-04-22T013026Z_741208741_GM1E94M0Q7101_RTRMADP_3_USA-EXPLOSIONS-BOSTON.JPG" align="left" title="A couple embraces at a memorial on Boylston Street to the victims of the Boston Marathon bombings in Boston" border="0" /></a>Some lawmakers fault the FBI for not following up on intelligence about one of the alleged bombers.</p><br clear="all"/></description><link>http://news.yahoo.com/boston-marathon-bombing-blame-game-begins-210800101.html</link><pubDate>Sun, 21 Apr 2013 17:08:00 -0400</pubDate><source url="http://www.csmonitor.com/">Christian Science Monitor</source><guid isPermaLink="false">boston-marathon-bombing-blame-game-begins-210800101</guid><media:content url="http://l3.yimg.com/bt/api/res/1.2/uiv31afw5K_BzPxeYQz44Q--/YXBwaWQ9eW5ld3M7Zmk9ZmlsbDtoPTg2O3E9ODU7dz0xMzA-/http://media.zenfs.com/en_us/News/Reuters/2013-04-22T013026Z_741208741_GM1E94M0Q7101_RTRMADP_3_USA-EXPLOSIONS-BOSTON.JPG" type="image/jpeg" ></media:content><media:text type="html"><p><a href="http://news.yahoo.com/boston-marathon-bombing-blame-game-begins-210800101.html"><img src="http://l3.yimg.com/bt/api/res/1.2/uiv31afw5K_BzPxeYQz44Q--/YXBwaWQ9eW5ld3M7Zmk9ZmlsbDtoPTg2O3E9ODU7dz0xMzA-/http://media.zenfs.com/en_us/News/Reuters/2013-04-22T013026Z_741208741_GM1E94M0Q7101_RTRMADP_3_USA-EXPLOSIONS-BOSTON.JPG" align="left" title="A couple embraces at a memorial on Boylston Street to the victims of the Boston Marathon bombings in Boston" border="0" /></a>Some lawmakers fault the FBI for not following up on intelligence about one of the alleged bombers.</p><br clear="all"/></media:text><media:credit role="publishing company"></media:credit></item></guid></channel>
</rss>
我的 feedViewController.m 如下：
@interface feedViewController ()
@end
@implementation feedViewController
@synthesize tableView,showPosts;
//@synthesize feed;
Feed *xmlParseFeed;
//channel *chShow;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self)
// Custom initialization
return self;
- (void)viewDidLoad
[super viewDidLoad];
//self.feed = [[Feed alloc] init];
self.showPosts = [[NSMutableArray alloc] init];
NSArray *newPosts = [xmlParseFeed newPosts];
if (newPosts)
[self.showPosts addObjectsFromArray:newPosts];
//[newPosts release];
static NSString *feedURLString = @"http://news.yahoo.com/rss";
NSURL *feedURL = [NSURL URLWithString:feedURLString];
xmlParseFeed = [[Feed alloc] initWithURL:feedURL];
self.showPosts = [[NSMutableArray alloc] init];
[xmlParseFeed refresh];
- (void)viewDidUnload
[self setTableView:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
return 1;
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
return [showPosts count];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] ;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
ItemDataCollection *post = [showPosts objectAtIndex:indexPath.row];
Feed *entry = [showPosts objectAtIndex:indexPath.row];
// Set up the cell...
channel *channelRecord = [self.showPosts objectAtIndex:indexPath.row];
cell.textLabel.text = channelRecord.cTitle;
cell.textLabel.text = channelRecord.pubDate;
NSLog(@"channelRecord.title *****************%@",channelRecord.cTitle);
/* cell.textLabel.text = post.title;
cell.textLabel.text = post.itemDescription;
cell.textLabel.text = post.titleImage;
NSLog(@"item title******%@",post.title); */
cell.textLabel.font=[UIFont fontWithName:@"Arial" size:12];
cell.textLabel.numberOfLines = 1;
return cell;
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
return (interfaceOrientation == UIInterfaceOrientationPortrait);
@end
Properties in channel class are: cTitle,pubDate and itemCollectionArray. Properties in Post class are: title, itemDescription and titleImage. Feed class is for parsing. the contents of Feed.m is as follows:
@class ItemDataCollection;
@implementation Feed
@synthesize feedURL,feedRequest,currentElement,currentElementData;
//@synthesize feedChannel;
//@synthesize feedPosts;
static ItemDataCollection *itemCollection;
static NSMutableArray *channelCollection;
NSMutableString *mString;
NSMutableString *str;
channel *Channel ;
- (NSArray *)newPosts
NSMutableArray *posts = [[NSMutableArray alloc] init];
for (NSInteger item = 1; item <= 5; item++)
//NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
ItemDataCollection *newPost;
newPost = [[ItemDataCollection alloc] init];
// NSString *pubDate = [NSDate dateWithTimeIntervalSinceNow:@"pubDate"];
newPost.title = [NSString stringWithFormat:@"title %@", kTitleElementName];
newPost.itemDescription = [NSString stringWithFormat:@"itemdescription %@", kItemDescription];
newPost.titleImage = [NSString stringWithFormat:@"image %@",kItemImage];
// newPost.itemTitle = [NSString stringWithFormat:@"itemtitle %@", ITEM_TITLE_XML];
[posts addObject:newPost];
//[newPost release];
// [pool drain];
return posts;
- (Feed *) initXMLParser
//[super init];
appDelegate = (appAppDelegate *)[[UIApplication sharedApplication] delegate];
return self;
-(id)initWithURL:(NSURL *)sourceURL
if (self = [super init])
self.feedURL = sourceURL;
channelCollection=[[NSMutableArray alloc] init];
return self;
- (void)refresh
self.feedRequest = [ASIHTTPRequest requestWithURL:feedURL];
// [feedPosts removeAllObjects];
[feedRequest setDelegate:self];
[feedRequest startAsynchronous];
- (void)requestFinished:(ASIHTTPRequest *)request
NSData *responseData = [request responseData];
// NSLog(@"*************response are *********%@",[[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding]);
NSXMLParser *parser = [[NSXMLParser alloc] initWithData:responseData];
[parser setDelegate:self];
if ([parser parse])
[[NSNotificationCenter defaultCenter]
postNotificationName:@"myevent"
object:nil];
// [posts ]
- (void)requestFailed:(ASIHTTPRequest *)request
NSError *error = [request error];
NSLog(@"requestFailed: %@", [error localizedDescription]);
- (void)parser:(NSXMLParser *)parser
didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName
attributes:(NSDictionary *)attributeDict
if ([elementName isEqualToString:kChannelElementName])
Channel = [[channel alloc] init];
dict=[[NSMutableDictionary alloc] init];
[Channel setItemCollectionArray:[[NSMutableArray alloc] init]];
return ;
if ([elementName isEqualToString:kItemElementName])
itemCollection=[[ItemDataCollection alloc] init];
return ;
if ([elementName isEqualToString:kTitleElementName])
return ;
if([elementName isEqualToString:kItemDescription])
return ;
if ([elementName isEqualToString:kItemImage])
NSString *urlString = attributeDict[@"url"];
if(urlString)
[dict setObject:urlString forKey:@"img"];
NSLog(@"%@",urlString);
mString = [NSString stringWithFormat:urlString];
str = [NSString stringWithFormat:mString];
return ;
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
if (currentElementData == nil)
self.currentElementData = [[NSMutableString alloc] init];
[currentElementData appendString:string];
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName
if ([elementName isEqualToString:kChannelElementName])
[channelCollection addObject:Channel];
NSLog(@"channel are***********%@",channelCollection);
for(ItemDataCollection *mydata in Channel.itemCollectionArray)
NSLog(@"___%@ <><><><><> desc \n <><><><><><> img \n %@",mydata.title,/*mydata.itemDescription*/mydata.titleImage);
Channel =nil;
else if ([elementName isEqualToString:kItemElementName])
[[Channel itemCollectionArray] addObject:itemCollection];
itemCollection=nil;
else if ([elementName isEqualToString:kTitleElementName])
if(itemCollection==nil)
Channel.cTitle=currentElementData;
else
itemCollection.title=currentElementData;
else if ([elementName isEqualToString:kPubDate])
Channel.pubDate=currentElementData;
else if ([elementName isEqualToString: kItemDescription])
if(itemCollection!=nil)
itemCollection.itemDescription = currentElementData;
else if([currentElementData rangeOfString:@"media:content"].location)
if(itemCollection!=nil)
if([str isEqualToString:mString])
// [currentElementData appendString:dict];
itemCollection.titleImage = mString;
else
itemCollection.titleImage = @"";
self.currentElementData = nil;
- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
NSString *info = [NSString stringWithFormat:
@"Error %i, Description: %@, Line: %i, Column: %i",
[parseError code],
[[parser parserError] localizedDescription],
[parser lineNumber],
[parser columnNumber]];
NSLog(@"RSS Feed Parse Error: %@", info);
@end
Feed 正在被解析，可以在控制台上看到。但它在屏幕上不可见。可能是什么原因？正如我之前所说， cellForRowAtIndexPath() 根本没有被访问。这是什么原因？？
我已经添加了这个方法：
- (void)feedChanged:(NSNotification *)notification
NSArray *newPosts = [xmlParseFeed newPosts];
NSLog(@"%@",newPosts);
if (newPosts)
[self.showPosts addObjectsFromArray:newPosts];
[self.tableView reloadData];
// [self updateViewTitle];
// [newPosts release];
【问题讨论】：
一旦检查数组 newPosts 是否具有值并将数据源添加到 tableview？ 您是否正确设置了代表@Crazed'nDazed 我在 viewDidLoad() 中打印了 newPosts，它显示为 null.... 为什么会这样？数据源和委托已使用故事板设置。 【参考方案1】：我看不到您在代码中的哪个位置从 UITableView 调用 reloadData。您需要在加载 newPosts 之后调用此方法。
如果这不起作用，请检查以下几项：
tableView:numberOfRowsInSection: 返回的值是多少？它大于零吗？如果它为零，这就是为什么不调用 tableView:cellForRowAtIndexPath 的原因。
如何加载 Feed？是在主线程还是其他线程？您应该在不同的线程中加载它，因此在加载数据时不会阻塞 UI，但请确保在将数据加载到 newPosts 后调用 reloadData。
【讨论】：
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