我正在尝试学习IOS开发，我从一个示例RSS提要应用程序创建了一个项目，该应用程序从我的服务器上的XML提要文件加载数据。这工作正常，但如果按下主页按钮，我希望它刷新（ios多任务处理）。我已经尝试过[table reloaddata]并把它放在所有的viewdidload / viewdiddisappear部分中，但是它没有工作，并且它没有停在我已经放在它们上面的断点上。
@implementation RootViewController
- (void)viewDidLoad {
// Add the following line if you want the list to be editable
// self.navigationItem.leftBarButtonItem = self.editButtonItem;
//[newsTable reloaddata];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [stories count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *MyIdentifier = @"MyIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier] autorelease];
}
// Set up the cell
int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1];
[cell setText:[[stories objectAtIndex: storyIndex] objectForKey: @"title"]];
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// Navigation logic
int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1];
NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"];
// clean up the link - get rid of spaces, returns, and tabs...
storyLink = [storyLink stringByReplacingOccurrencesOfString:@" " withString:@""];
storyLink = [storyLink stringByReplacingOccurrencesOfString:@"\n" withString:@""];
storyLink = [storyLink stringByReplacingOccurrencesOfString:@" " withString:@""];
NSLog(@"link: %@", storyLink);
// open in Safari
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:storyLink]];
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[newsTable reloadData];
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if ([stories count] == 0) {
[newsTable reloadData];
NSString * path = @"http://www.myserver.co.uk/test.xml";
[self parseXMLFileAtURL:path];
//[NSTimer scheduledTimerWithTimeInterval:10 target:self selector:@selector(reloadData) userInfo:nil repeats:FALSE];
}
cellSize = CGSizeMake([newsTable bounds].size.width, 60);
}
-(void)viewWillDisappear:(BOOL)animated {
[newsTable reloadData];
}
- (void)viewDidDisappear:(BOOL)animated {
[newsTable reloadData];}
- (void)applicationDidBecomeActive:(UIApplication *)application {
/*
Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
*/
[newsTable reloadData];
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
/*
Called as part of transition from the background to the inactive state: here you can undo many of the changes made on entering the background.
*/
[newsTable reloadData];
}
- (void)parserDidStartDocument:(NSXMLParser *)parser{
NSLog(@"found file and started parsing");
}
- (void)parseXMLFileAtURL:(NSString *)URL
{
stories = [[NSMutableArray alloc] init];
//you must then convert the path to a proper NSURL or it won't work
NSURL *xmlURL = [NSURL URLWithString:URL];
// here, for some reason you have to use NSClassFromString when trying to alloc NSXMLParser, otherwise you will get an object not found error
// this may be necessary only for the toolchain
rssParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
// Set self as the delegate of the parser so that it will receive the parser delegate methods callbacks.
[rssParser setDelegate:self];
// Depending on the XML document you're parsing, you may want to enable these features of NSXMLParser.
[rssParser setShouldProcessNamespaces:NO];
[rssParser setShouldReportNamespacePrefixes:NO];
[rssParser setShouldResolveExternalEntities:NO];
[rssParser parse];
}
- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
NSString * errorString = [NSString stringWithFormat:@"Unable to download story feed from web site (Error code %i )", [parseError code]];
NSLog(@"error parsing XML: %@", errorString);
UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle:@"Error loading content" message:errorString delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
[errorAlert show];
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
//NSLog(@"found this element: %@", elementName);
currentElement = [elementName copy];
if ([elementName isEqualToString:@"item"]) {
// clear out our story item caches...
item = [[NSMutableDictionary alloc] init];
currentTitle = [[NSMutableString alloc] init];
currentDate = [[NSMutableString alloc] init];
currentSummary = [[NSMutableString alloc] init];
currentLink = [[NSMutableString alloc] init];
}
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
//NSLog(@"ended element: %@", elementName);
if ([elementName isEqualToString:@"item"]) {
// save values to an item, then store that item into the array...
[item setObject:currentTitle forKey:@"title"];
[item setObject:currentLink forKey:@"link"];
[item setObject:currentSummary forKey:@"summary"];
[item setObject:currentDate forKey:@"date"];
[stories addObject:[item copy]];
NSLog(@"adding story: %@", currentTitle);
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
//NSLog(@"found characters: %@", string);
// save the characters for the current item...
if ([currentElement isEqualToString:@"title"]) {
[currentTitle appendString:string];
} else if ([currentElement isEqualToString:@"link"]) {
[currentLink appendString:string];
} else if ([currentElement isEqualToString:@"description"]) {
[currentSummary appendString:string];
} else if ([currentElement isEqualToString:@"pubDate"]) {
[currentDate appendString:string];
}
}
- (void)parserDidEndDocument:(NSXMLParser *)parser {
[activityIndicator stopAnimating];
[activityIndicator removeFromSuperview];
NSLog(@"all done!");
NSLog(@"stories array has %d items", [stories count]);
[newsTable reloadData];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning]; // Releases the view if it doesn't have a superview
// Release anything that's not essential, such as cached data
}
- (void)dealloc {
[currentElement release];
[rssParser release];
[stories release];
[item release];
[currentTitle release];
[currentDate release];
[currentSummary release];
[currentLink release];
[super dealloc];
}
@end
答案 0 :(得分：3)
我喜欢使用通知来处理这种情况。将此行代码添加到“viewDidLoad”方法
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(updateRSSFeed)
name:UIApplicationWillEnterForegroundNotification
object:nil];
'updateRSSFeed'方法将执行类似这样的操作
- (void) updateRSSFeed
{
NSLog( @"Feed Me!!!");
// Code to restart loading the data from the RSS feed and ultimately reloading
// the table view.
}
并且不要忘记删除观察者，因此将其添加到'dealloc'方法
[[NSNotificationCenter defaultCenter] removeObserver: self];
在具有多个视图控制器的复杂应用程序中，可以在不退出应用程序的情况下取消分配视图控制器，并且可能会向不存在的实例发送通知，从而导致崩溃。
通知非常有用，因此请深入了解文档和其他来源，以了解如何使用它们。
最后，方法'applicationDidBecomeActive：'和'applicationWillEnterForeground：'将永远不会在根视图控制器中调用，因为它们是appDelegate遵守的应用程序委托协议的一部分。
答案 1 :(得分：0)
嘿，如果你想对应用程序进入后台做出反应，你应该实现
- (void)applicationDidEnterBackground:(UIApplication *)application
，并从那里触发数据重新加载。当应用程序进入后台时（即，当您“最小化”它，按主页按钮或切换到其他应用程序时，不会调用viewWillAppear。
干杯
答案 2 :(得分：0)
我不清楚你打电话给[tableView reloadData]的地方。根据您的描述，您必须在applicationWiilResignActive:期间调用它，但除非您已向操作系统指明要在后台下载，否则很可能无法运行。
但是我相信在调用此方法之前你必须有已经开始下载，这将解释为什么你看不到表重新加载或断点被调用。
我可能误解了你是如何进行通话的，但我认为你有一个基本的设计问题，因为你无法启动在停用时重新加载。