有人可以识别并修复我的iOS拉动以刷新代码吗?

Question

这是我的第一个应用程序，我正在尝试实现拉动以刷新控件。我遇到了路障。有人可以识别并修复我的代码吗？拉取刷新动画有效，但表中的 XML 数据不会刷新。提前谢谢你。

#import "MasterViewController.h"
#import "DetailViewController.h"
@interface MasterViewController () {
    NSXMLParser *parser;
    NSMutableArray *feeds;
    NSMutableDictionary *item;
    NSMutableString *title;
    NSMutableString *link;
    NSString *element;
}
@end
@implementation MasterViewController
- (void)awakeFromNib
{
    [super awakeFromNib];
}
//Paste Blog feed here
- (void)viewDidLoad {
    [super viewDidLoad];
    feeds = [[NSMutableArray alloc] init];
    NSURL *url = [NSURL URLWithString:@"http://Placeholder.xml"];
    parser = [[NSXMLParser alloc] initWithContentsOfURL:url];
    [parser setDelegate:self];
    [parser setShouldResolveExternalEntities:NO];
    [parser parse];
    UIRefreshControl *refreshControl = [UIRefreshControl new];
    [refreshControl addTarget:self action:@selector(refresh:) forControlEvents:UIControlEventValueChanged];
    refreshControl.attributedTitle = [[NSAttributedString alloc] initWithString:@"Pull to refresh..."];
    self.refreshControl = refreshControl;
    [self.tableView reloadData];
}
- (void)refresh:(UIRefreshControl *)sender
{
    // ... your refresh code
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    NSURLSession *session = [NSURLSession sharedSession];
    [[session dataTaskWithURL:[NSURL URLWithString:@"http://Placeholder.xml"]
            completionHandler:^(NSData *data,
                                NSURLResponse *response,
                                NSError *error) {
                // handle response
                NSXMLParser *updatedParser = [[NSXMLParser alloc] initWithData:data];
                [updatedParser parse];
                [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
            }] resume];
    [sender endRefreshing];
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

#pragma mark - Table View

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return feeds.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
    cell.textLabel.text = [[feeds objectAtIndex:indexPath.row] objectForKey: @"title"];
    return cell;
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {
    element = elementName;
    if ([element isEqualToString:@"item"]) {
        item    = [[NSMutableDictionary alloc] init];
        title   = [[NSMutableString alloc] init];
        link    = [[NSMutableString alloc] init];
    }
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
    if ([elementName isEqualToString:@"item"]) {
        [item setObject:title forKey:@"title"];
        [item setObject:link forKey:@"link"];
        [feeds addObject:[item copy]];
    }
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
    if ([element isEqualToString:@"title"]) {
        [title appendString:string];
    } else if ([element isEqualToString:@"link"]) {
        [link appendString:string];
    }
}
- (void)parserDidEndDocument:(NSXMLParser *)parser {
    [self.tableView reloadData];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([[segue identifier] isEqualToString:@"showDetail"]) {
        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
        NSString *string = [feeds[indexPath.row] objectForKey: @"link"];
        [[segue destinationViewController] setUrl:string];
    }
}

@end

Answer 1

您需要

告诉您的UITableView何时应该自行刷新。目前，您下载了新数据，但您不对其进行任何操作。

您要么想在表视图上调用 -reloadData 方法，要么如果您只想加载特定的部分/行范围，则需要调用其他重新加载方法之一。您应该在分析完已下载的新数据并准备好显示它后调用它。