Memory leakage when button is pressed

Question

I am trying to make a simples application where the user can go through notes and then do a quiz. I am presenting this notes as images and the image would be assigned to an UIImageView to be shown to the user.

In my view did load I am mostly setting the UI. Then I would be creating my array containing my array of images (notes)

- (void)viewDidLoad {
    UIColor *colourForNavigationBar = [self colorWithHexString:@"919D9F"];
    [[UINavigationBar appearance] setBarTintColor:colourForNavigationBar];
    UIColor *colourForBackground = [self colorWithHexString:@"F0F3F4"];
    self.view.backgroundColor = colourForBackground;
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
    label.backgroundColor = [UIColor clearColor];
    label.font = [UIFont boldSystemFontOfSize:27.0];
    label.textAlignment = NSTextAlignmentCenter;
    label.textColor = [UIColor whiteColor];
    self.navigationItem.titleView = label;
    label.text = @"Notes";
    [label sizeToFit];
    UIColor *colourForButton = [self colorWithHexString:@"919D9F"];
    self.previousButton.backgroundColor = colourForButton;
    self.nextButton.backgroundColor = colourForButton;
    finishedNotes = NO;
    playerPlaying = NO;
    arrayOfImages = [NSArray arrayWithObjects:
                     [UIImage imageNamed:@"1.png"],
                     [UIImage imageNamed:@"2.png"],
                     [UIImage imageNamed:@"3.png"],
                     [UIImage imageNamed:@"4.png"],
                     [UIImage imageNamed:@"5.png"],
                     [UIImage imageNamed:@"6.png"],
                     [UIImage imageNamed:@"7.png"],
                     [UIImage imageNamed:@"8.png"],
                     [UIImage imageNamed:@"9.png"],
                     [UIImage imageNamed:@"10.png"],
                     [UIImage imageNamed:@"11.png"],
                     [UIImage imageNamed:@"12.png"],
                     [UIImage imageNamed:@"13.png"],
                     nil];
}

Then there is the 'next' button which allows the user to continue on to the next note. Below is the code for the action

- (IBAction)nextNote:(id)sender {
    if (finishedNotes == YES) {
        [self performSegueWithIdentifier:@"quizFromNotes" sender:self];
    }
    self.previousButton.enabled = YES;
    stateOfPhoto++;
    if (stateOfPhoto < 13) {
        UIImage *image = [arrayOfImages objectAtIndex:stateOfPhoto-1];
        self.imageView.image = image;
    }
    if (stateOfPhoto == 13) {
        UIImage *image = [arrayOfImages objectAtIndex:stateOfPhoto-1];
        self.imageView.image = image;
        [self.nextButton setTitle:@"Begin Quiz" forState:UIControlStateNormal];
        finishedNotes =YES;
    }
    if (playerPlaying == YES) {
        [self.notesPlayer stop];
        playerPlaying = NO;
    }
}

Everything is working fine and smoothly. However whenever there is the change of image, the memory used by the application increasing by a few megabytes. Below is the photo of the memory usage.

From the black line onwards, when I press the 'next' button, the memory used increases. It just repeats itself until the user has continued onto the quiz. If I end the quiz and start over the notes, the memory usage would continue to rise from the previous memory usage (73 mb). Eventually, the app would crash and I cannot launch the app anymore.

I have never faced memory leakage issues before and hence, I am not sure of what to do. I have tried googling for the past hour and am not able to come up with a solution to this. So my question is how would I be able to release the memory or reduce the memory usage.

Answer 1

I think it's because of your images, how big are those images you're showing?

Based on this answer: https://stackoverflow.com/a/22662754/3231194 , you can either use this method to scale your images before putting them into your UIImageView :

-(UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
    //UIGraphicsBeginImageContext(newSize);
    // In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution).
    // Pass 1.0 to force exact pixel size.
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

But that will take up a CPU usage (I'm not sure though if it is a big deal).

OR

You can just resize your images by yourself before importing them to your Xcode project.