Question

I’m making a form that allows the user to enter datas in my IOS application. This form allows the user to enter a lot of repetive datas. So, sometimes, the process takes time and I would like to display a UIActivityIndicatorView during this process.

Unfortunalty the spinner appears only one second or less at the end of the process, not at the beginning as expected.

There is some code :

- (void) manageSpinner{
    spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    [spinner setCenter:CGPointMake(self.view.bounds.size.width/2.0, self.view.bounds.size.height/2.0)]; // I do this becau I'm in landscape mode
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:self.tableView.bounds];
    UIImage *image = [UIImage imageNamed:@"dark_gradiant.jpg"];
    [imageView setImage:image];
    [imageView addSubview:spinner];
    [self.tableView addSubview:imageView];
    [spinner startAnimating];
}


//On click save by the user
- (IBAction)save:(id)sender{

    //Collect information from the form

    myObject.name = nameTF.text;

    [...]

    if(informations OK[...]){        
        //Manage spinner
        [self manageSpinner];

        //Add : this is the long process
        for (int i=0; i<nbRepeatChooseByUser; i++) {
            [myObject register];
        }

        //Call the delegate that will dismiss the form
        [self.delegate theSaveButtonOnTheAddMyObjectTVCWasTapped:self];
    }
}

The spinner is called before the adding method but it seems to be set up after the process.

Thank you,

Alexandre

Answer 1

The activity indicator is running on the same thread as your long process thus the animation does not start as soon as you want. Try to run your long process in the background thread.

if(informations OK[...]){        
    //Manage spinner
    [self manageSpinner];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
        // Do your background process here
        //Add : this is the long process
        for (int i=0; i<nbRepeatChooseByUser; i++) {
            [myObject register];
        }

        dispatch_async(dispatch_get_main_queue(), ^{
            //This section will be called after your long process has been completed.

            //Call the delegate that will dismiss the form
            [self.delegate theSaveButtonOnTheAddMyObjectTVCWasTapped:self];
        });

    });

}