直到我滚动数据才在UITableView中加载 [英] Data doesn't load in UITableView until I scroll

问题描述

我正在尝试将解析的数据加载到单元格中，但是问题是它正在同步发生，并且UitableView在数据加载完成之前不会显示.我试图通过使用performSelectorInBackground解决问题，但是现在直到开始滚动才将数据加载到单元格中.这是我的代码:

I am trying to load parsed data in cells, but the problem is that it is happening synchronously and UitableView doesn't show until the data has finished loading. I tried to solve the problem by using performSelectorInBackground, but now data isn't loaded in the cells until I start scrolling. Here is my code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    [self performSelectorInBackground:@selector(fethchData) withObject:nil];


}


- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
self.listData = nil;
    self.plot=nil;
}


-(void) fethchData

{
    NSError *error = nil;
    NSURL *url=[[NSURL alloc] initWithString:@"http://www.website.com/"];
    NSString *strin=[[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];

    HTMLParser *parser = [[HTMLParser alloc] initWithString:strin error:&error];

    if (error) {
        NSLog(@"Error: %@", error);
        return;
    }

    listData =[[NSMutableArray alloc] init];
    plot=[[NSMutableArray alloc] init];

    HTMLNode *bodyNode = [parser body];
    NSArray *contentNodes = [bodyNode findChildTags:@"p"];


    for (HTMLNode *inputNode in contentNodes) {
            [plot addObject:[[inputNode allContents] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]];    
        }


    NSArray *divNodes = [bodyNode findChildTags:@"h2"];

    for (HTMLNode *inputNode in divNodes) {

            [listData addObject:[[inputNode allContents] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]];          

        }
    }


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

    static NSString *CellIdentifier = @"Cell";
    //here you check for PreCreated cell.
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
        cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    }

    //Fill the cells...  


    cell.textLabel.text = [listData objectAtIndex:indexPath.row];
    cell.textLabel.font = [UIFont boldSystemFontOfSize:14];
    cell.textLabel.numberOfLines=6; 
    cell.textLabel.textColor=[UIColor colorWithHue:0.7 saturation:1 brightness:0.4 alpha:1];


    cell.detailTextLabel.text=[plot objectAtIndex:indexPath.row];
    cell.detailTextLabel.font=[UIFont systemFontOfSize:11];
    cell.detailTextLabel.numberOfLines=6;

    return cell;


}

推荐答案

在成功加载数据后，将其放在某个地方:

Put this somewhere after the data is loaded successfully:

dispatch_async(dispatch_get_main_queue(), ^{
    [self.tableView reloadData];
});

此修复了不在主线程中时调用GUI更新的问题.

This fix the problem of calling a GUI update while you're not in the main thread.

此代码使用Apple的GCD技术强制重新加载数据功能在主线程上运行.进一步了解 并发编程指南以获得更多理解(这是一个很大的领域，因此很难在评论中进行解释) 无论如何，如果您不太了解它，则不建议这样做，因为它会使程序在少数情况下崩溃.

This code uses the GCD Technology from Apple to force the reload data function to run on main thread. Read more about Concurrency Programming Guide for more understanding (it's quite large field so that it's hard to explain in the comment) Anyway, it's not very recommended if you don't understand it well because it causes the program to crash some rare cases.

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