CODEWITHSUNDEEP
iosobjective-cuiview
abc123
abc123

Reputation: 8303

How to update UIView before next method is called in Objective-C

I'm trying to update my textView on screen before it starts downloading data. Right now, it only updates the view after all of the downloads are complete. How can I do it before or in between the downloads?

Edit: I want the self.textView.text = @"Connection is good, start syncing..."; to update the UI before the downloading starts. But right now, it only updates after the download finishes.

Here is what the code looks like. 

if ([self.webApp oAuthTokenIsValid:&error responseError:&responseError]) {
    self.textView.text = @"Connection is good, start syncing...";
    [self.textView setNeedsDisplay];

    [self performSelectorInBackground:@selector(downloadCustomers:) withObject:error];
}

I'm new to this and have yet to learn how threads work, but from what I read, the downloadCustomers function should be using a background thread leaving the main thread to update the UI.

Upvotes: 0

Views: 561

Answers (2)

Vishal Singh
Vishal Singh

Reputation: 4480

if ([self.webApp oAuthTokenIsValid:&error responseError:&responseError]) {
    self.textView.text = @"Connection is good, start syncing...";
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
      [self downloadCustomers];
      dispatch_async(dispatch_get_main_queue(), ^{
        //Do whatever you want when your download is finished, maybe self.textView.text = @"syncing finished"
      });
});
}

Upvotes: 1

svena
svena

Reputation: 2779

The pattern here is to initialize your download on background thread and then call back to main thread for UI update.

Below is an example using GCD. The advantage of GCD version is that you can consider using whatever you do in -downloadCustomers, to insert in-line where you call it.

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
   [self downloadCustomers];
      dispatch_async(dispatch_get_main_queue(), ^{
         [self.textView setNeedsDisplay];
      });
});

Upvotes: 1

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