CODEWITHSUNDEEP
iosgrand-central-dispatchmbprogresshud
anna
anna

Reputation: 2723

dispatch_async and frame rate

I'm trying to learn GCD, so I don't have a full grasp on how it works yet. For some reason, I experience a permanent drop in frame rate after I call the following method. If I don't use the dispatch functions and simply write the data on the main loop, the frame rate stays at 60. I don't know why.

-(void)saveDataFile {


        _hud = [MBProgressHUD showHUDAddedTo:self.parentView animated:YES];
        _hud.labelText = NSLocalizedString(@"Saving data...", nil);


        dispatch_queue_t myQueue = dispatch_queue_create("myQueueName", NULL);


        dispatch_async(myQueue, ^(void) {

            @autoreleasepool {

                id data = [self.model getData];
                if (data != nil) {

                    NSString *filePath = @"myPath";
                    [data writeToFile:filePath atomically:YES];
                }

            }


            dispatch_async(dispatch_get_main_queue(), ^(void) {

                [_hud hide:YES];

            });

        });


    }

Upvotes: 1

Views: 319

Answers (1)

anna
anna

Reputation: 2723

Solved. I followed the implementation of HUD from this question: MBProgressHUD not showing

Basically, I need to remove the HUD rather than simply hide it. Otherwise the HUD animation continued, invisible to me, hence causing the drop in frame rate. 

-(void)saveDataFile {


// create HUD and add to view
    MBProgressHUD *hud = [[MBProgressHUD alloc]initWithView:self.parentView];
    hud.labelText = NSLocalizedString(@"Saving data...", nil);
    hud.delegate = self;
    [self.parentView addSubview:hud];


// define block for saving data

        void (^saveData)() = ^() {

            @autoreleasepool {

                id data = [self.model getData];
                if (data != nil) {

                    NSString *filePath = @"myPath";
                    [data writeToFile:filePath atomically:YES];
                }

            }

}


// use HUD convenience method to run block on a background thread
[hud showAnimated:YES whileExecutingBlock:saveData];


    }


// remove hud when done!
//
- (void)hudWasHidden:(MBProgressHUD *)hud {

    [hud removeFromSuperview];
}

Upvotes: 1

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