ios - 在 UITableView 加载数据之前，MasterViewController 中添加的 View 不可见

Question

我在 MAster Detail 应用程序中有一个 MasterViewController，在 UITableView 中显示数据。

数据是从互联网批量加载的，因此当第一次加载数据到达时，我会显示一个带有下载事件的 UIView。

虽然 UITableView 上没有加载数据，但事件指示器 View 不可见。然后，在加载此数据并且应用程序继续加载更多数据后，将显示事件指示器 View 。

我的 MasterViewController 实现了委托(delegate)方法，以便在每批数据的下载过程开始和结束时收到通知。

• 为什么第一次调用该方法时，AEMEventosListDidStartLoadingEventos: 中加载的 UIView (self.downloadingProgrssView) 不可见？

代码如下:

-(void)AEMEventosListDidStartLoadingEventos:(AEMEventosList *)evList
{

// The views created here are not displayed the first time this method is called while the UITableView has no data.
//Once the TableView has been filled the followings calls to this method get the UIView displayed.

    //Crear una vista con un idicador de progreso.

    //Ancho y alto de activity Indicator
    int widthAndHeigth = 30;
    //Tamaño de activityIndicator
    CGRect activityViewFrame = CGRectMake(10, 5, 20, 20);
    //Tamaño de titleView
    CGRect titleViewFrame = CGRectMake(widthAndHeigth + 20, 0, self.parentViewController.view.frame.size.width - widthAndHeigth, widthAndHeigth);
    //Tamaño de downloadgingProgressView
    CGRect downloadingProgressFrame = CGRectMake(0 + 20, self.parentViewController.view.frame.size.height - widthAndHeigth, self.parentViewController.view.frame.size.width - 40, widthAndHeigth + 13);

    //Leyenda de la ventana.
    NSString *title;
    switch (evList.downloadingEventosGroupFlag) {
        case 0:
            title = NSLocalizedString(@"Downloading today's events", @"Downloading today's events leyend.");
            break;
        case 1:
            title = NSLocalizedString(@"Downloading events in a week", @"Downloading events in a week leyend.");
            break;
        case 2:
            title = NSLocalizedString(@"Downloading events in a month", @"Downloading events in a month leyend.");
            break;
        case 3:
            title = NSLocalizedString(@"Downloading later events", @"Downloading later events leyend.");
            break;            
        default:
            title = @"";
            break;
    }


    UIActivityIndicatorView *acView = [[UIActivityIndicatorView alloc] initWithFrame:activityViewFrame];
    acView.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhite;
    acView.hidesWhenStopped = NO;
    acView.tag = kActivityIndicatorViewTag;
    [acView startAnimating];

    UILabel *titleView = [[UILabel alloc] initWithFrame:titleViewFrame];
    titleView.text = title;
    titleView.font = [UIFont systemFontOfSize:11];
    titleView.backgroundColor = [UIColor clearColor];
    titleView.textColor = [UIColor whiteColor];
    titleView.tag = kNameViewTag;

    UIView *aux = [[UIView alloc] init];
    self.downloadingProgressView = aux;
    [aux release];
    self.downloadingProgressView.frame = downloadingProgressFrame;
    self.downloadingProgressView.backgroundColor = [UIColor colorWithRed:0.3 green:0.4 blue:0.6 alpha:0.9];
//    self.downloadingProgressView.tag = kDownloadingProgessViewTag;    
    downloadingProgressView.layer.cornerRadius = 13;

    [self.downloadingProgressView addSubview:acView];
    [self.downloadingProgressView addSubview:titleView];
    [acView release];
    [titleView release];

    //Añadir la vista y animar
    [self.parentViewController.view addSubview:self.downloadingProgressView];    
    [self.downloadingProgressView setFrame:CGRectMake( 20.0f, 480.0f, 280.0f, 480.0f)]; //notice this is OFF screen!
    [UIView beginAnimations:@"animateTableView" context:nil];
    [UIView setAnimationDuration:0.5];
    [self.downloadingProgressView setFrame:downloadingProgressFrame]; //notice this is ON screen!
    [UIView commitAnimations];

}


-(void)AEMEventosListDidFinishLoadingEventos:(id)evList {

    //Reasignar ls nueva lista de eventos descargada
    self.eventosList = evList;
    //Recargar la tabla
    [self.tableView reloadData];
    //Eliminar la vista de progreso de descarga y animar
    [UIView beginAnimations:@"animateTableView" context:nil];
    [UIView setAnimationDuration:0.5];
    [self.downloadingProgressView setFrame:CGRectMake( 20.0f, 480.0f, 280.0f, 480.0f)]; //notice this is OFF screen
    [UIView commitAnimations];
    self.downloadingProgressView = nil;
}


-(void)AEMEventosListDownloadingError:(AEMEventosList *)eventosList withError:(NSError *)error {

    //Eliminar la vista de progreso de descarga
    [[self.parentViewController.view viewWithTag:kDownloadingProgessViewTag] removeFromSuperview];

    //Log el error
    NSLog(@"%@", error);

    //Mostrar un mensaje de error
    UIAlertView *alertView = [[UIAlertView alloc] 
                              initWithTitle:NSLocalizedString(@"Download error", @"Alert View title for download error") 
                              message:[error localizedDescription] 
                              delegate:nil 
                              cancelButtonTitle:@"Ok" 
                              otherButtonTitles:nil];
    [alertView show];
    [alertView release];
}

Answer 1

问题是我在 ApplicationDidFinishLaunching 中加载主视图之前在 appController 中启动下载过程。对委托(delegate)方法的第一次调用速度太快，当我附加 View 时，应用程序的主视图没有显示。

我只需在 applicationdidFinishLaunchingWithOptions 方法中的此代码之后移动代码即可开始下载，一切都开始正常工作。

self.navigationController = [[[UINavigationController alloc] initWithRootViewController:masterViewController] autorelease];
self.navigationController.toolbarHidden = NO;
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];