Question

I have a tableView, and a “Reload” button that fetches data from a URL and reloads the table, a costly operation (in particular the fetch part).

I want display info to the user while this is happening, so I thought I’d put up a “Loading” UITextView on top, do the fetch/reload operation, then remove the UITextView.

Here’s the code:

- (IBAction)refreshData:(id)sender {

    UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height-30, self.view.frame.size.width, 30)];
    [self.view addSubview:textView];
    textView.text = @"Loading..";
    textView.textColor = [UIColor whiteColor];
    textView.backgroundColor = [UIColor grayColor];
    textView.editable = NO;

    [self fetchData];
    [self.tableView reloadData];

    [textView removeFromSuperview];
}

The behavior I get is that the fetchData executes before the UITextView renders on screen. I know this because I have NSLogs inside fetchData that execute before the UITextView shows up on screen.

Is there something obvious I’m missing here? Thanks.

Answer 1

Replace [self fetchData]; with

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

Then inside your fetchData method, after your fetch is done, add

[self performSelectorOnMainThread:@selector(fetchDataFinished) withObject:nil waitUntilDone:NO];

where the new method fetchDataFinished is defined as

-(void) fetchDataFinished{
    [self.tableView reloadData];
    [self.textView removeFromSuperview];
}

Note that you have to make textView a property so it is accessible in this method.

I have not tried out the above for your particular case, but I have used similar constructs successfully in many similar situations.