Question

We have developed map base application. We have implemented multi-threading for display data on map view. While application is running longer(around 20 min), Application will display memory warning level-1. And after couple of minutes it will give memory warning level-2 and after level2 application will be crash or goes to sleep.

We have checked memory leaks, Zombies lot’s of time. But there is no memory leak and zombie in our application.

Please advice how to handle memory warning level. Please draw some line to overcome memory level warning.

////Update…
I found that memory usage increase because of

CGContextRef context = UIGraphicsGetCurrentContext();

I have used multithreading for draw poly-annotation and for that i used CGContextRef which increases my memory usage whenever i call it.

i don’t know how release context because if i release it than next time it shows me

Invalid Context error i am positing my drawing code here.Please help me if anybody have any idea.

-(void) drawRect:(CGRect)rect {
NVPolylineAnnotation* annotation = self.annotation;

CGFloat POLYLINE_WIDTH = 9;

if(annotation.getZoomLevel == 7) {
    POLYLINE_WIDTH = 1.5;
}
else if(annotation.getZoomLevel == 8) {
    POLYLINE_WIDTH = 2.5;
}
else if(annotation.getZoomLevel ==9) {
    POLYLINE_WIDTH = 3;   
}    
else if(annotation.getZoomLevel ==10) {
    POLYLINE_WIDTH = 3.4;   
}    
else if(annotation.getZoomLevel == 11) {
    POLYLINE_WIDTH = 4;
}    
else if(annotation.getZoomLevel <= 13) {
    POLYLINE_WIDTH = 4.3;
}
else if (annotation.getZoomLevel == 14) {
    POLYLINE_WIDTH = 5.4;
}
else if(annotation.getZoomLevel == 15) {
    POLYLINE_WIDTH = 8;
}


CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, rect);
CGContextSetLineWidth(context, POLYLINE_WIDTH);
CGContextSetAlpha(context, 0.6);    

for(NSDictionary *route in annotation.routes) {

    NSString *locations = [route valueForKey:@"Locations"];
    double speed = [[route valueForKey:@"Speed"] doubleValue];


    if (locations && ([locations length]/16 > 1)) {       

        UIColor *color;
        if (speed <= 20) {
            color = [UIColor colorWithRed:222/255.0 green:0/255.0 blue:0/255.0 alpha:1.0];
        }
        else if (speed <= 40) {
            color = [UIColor colorWithRed:253/255.0 green:91/255.0 blue:2/255.0 alpha:1.0];
        }
        else if (speed <= 60) {
            color = [UIColor colorWithRed:253/255.0 green:145/255.0 blue:4/255.0 alpha:1.0];
        }
        else if (speed <=80) {
            color = [UIColor colorWithRed:255/255.0 green:212/255.0 blue:4/255.0 alpha:1.0];
        }
        else if (speed >80) {
            color = [UIColor colorWithRed:42/255.0 green:176/255.0 blue:39/255.0 alpha:1.0];
        }

        CGContextSetStrokeColorWithColor(context, color.CGColor);

        for (int i = 0; i <= locations.length - 32; i += 32) {

            CLLocationCoordinate2D coordinates;
            coordinates.latitude = hexDecode([locations substringWithRange:NSMakeRange(i, 16)]);
            coordinates.longitude = hexDecode([locations substringWithRange:NSMakeRange(i+16, 16)]);

            CGPoint point = [_mapView convertCoordinate:coordinates toPointToView:self];

            if (i == 0)
                CGContextMoveToPoint(context, point.x, point.y);
            else
                CGContextAddLineToPoint(context, point.x, point.y);
        }
        [self setNeedsDisplay];
        CGContextStrokePath(context);

    }   
}   
context = NULL;
UIGraphicsEndImageContext();    

}

Thanks In Advance.

Answer 1

The first thing you need to do is measure your application to figure out where the memory growth is coming from. While you may have no leaks, you obviously have a memory growth problem. One tool that will help you identify where memory growth is coming from is the Allocations tools in Instruments. Specifically, you can use a technique called heapshot analysis to help narrow down what is causing the growth in your application. For more information, checkout this post on heapshot analysis.