CODEWITHSUNDEEP
iosobjective-cswiftprogress-bar
Yatendra
Yatendra

Reputation: 1316

ProgressView not updating in iOS

I know this question asked many times on StackOverflow, But I already checked that. my problem is I am updating progress bar like this on main thread after getting response from api hit

dispatch_async(dispatch_get_main_queue(),^{

     for (int i = 0; i < 5000; i++) 
     {
        NSLog(@"%f",i);
        [progressView setProgress:i/5000 animated:YES];
     }
 });

from this way My progressivew not updating but when I set static digit it's working

[progressView setProgress:0.7 animated:YES];

After searching I found that there is issue regarding float decimal number digits. Because i/5000 give 0.000000 always even on 4999/5000. So after some googling I chnaged 

dispatch_async(dispatch_get_main_queue(),^{

     for (int i = 0; i < 5000; i++) 
     {
        float f = (float)i/5000;
        [progressView setProgress:f animated:YES];
     }
 });

now it's updating but progress view not update continuously, it's track update in last at once from 0 to 1

Upvotes: 0

Views: 313

Answers (2)

Yatendra
Yatendra

Reputation: 1316

@trapper you are right, thanks for help me but I got this solution before a min ago, no problem. Here I am posting my answer to help another guys.

This was a thread issue. The drawing of progress are stacked in the main queue and executed only at some point, at the end.

So the solution is to run the loop in a user thread, and call the main thread when you need to draw (that is compulsory). So, change update progress as follows

dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){
                //Background Thread
                for (int i = 0; i < 50000; i++) {

                     float f = (float)i/50000;;

                    dispatch_async(dispatch_get_main_queue(), ^(void){

                        //Run UI Updates

                        [self->progressView setProgress:f animated:YES];

                    });
                }
            });

Upvotes: 0

trapper
trapper

Reputation: 12003

The first issue you got right, the integer division is always going to give you 0.

The second issue is that the UI updates on the main thread - and only periodically even then. Now your code is also running on the main thread, so the UI is completely blocked while your code executes. It will only get a chance to update after your code ends, so you will only ever see the final value actually get rendered.

Upvotes: 1

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