Lag while drawing in ios7

Question

I am having an app in which I am doing some sketching on a view.

So far, it was working fine until I installed ios7.

My app uses touches moved met

Answer 1

Here's listed same code with same problem on ios7 https://stackoverflow.com/questions/18198129/ios-7-making-my-apps-drawing-algorithm-lag people suggest moving drawing logic into drawRect:

Answer 2

To find a instant solution, Replace this line

 mainImage.image = UIGraphicsGetImageFromContext(UIGraphicsGetCurrentContext());

with

[mainImage performSelectorInBackground:@selector(setImage:) withObject:UIGraphicsGetImageFromCurrentImageContext()];

If you need an elaborate and accurate solution try to replace the MoveTo with CGMutablepath . Hope this helps.

Answer 3

we have solved this problem using dispatch_async(dispatch_get_main_queue(), ^{)}; block in touchMoved method like this :

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{

        dispatch_async(dispatch_get_main_queue(), ^{
        mouseSwiped = YES;
        UITouch *touch = [touches anyObject];
        if(touch.view==self.vwSwipePage)
        {
            return;
        }
        if(flagIsEraser)
        {
            CGPoint currentPoint;
            if(flagActiveViewPage)
            {

                currentPoint = [touch locationInView:self.mainImage];
                UIGraphicsBeginImageContext(self.mainImage.frame.size);
                [self.mainImage.image drawInRect:CGRectMake(0, 0, self.mainImage.frame.size.width, self.mainImage.frame.size.height)];
            }
            else
            {
                currentPoint = [touch locationInView:self.mainImage1];
                UIGraphicsBeginImageContext(self.mainImage1.frame.size);
                [self.mainImage1.image drawInRect:CGRectMake(0, 0, self.mainImage1.frame.size.width, self.mainImage1.frame.size.height)];
            }

            //clear using circle brush........
            CGContextRef context = UIGraphicsGetCurrentContext();
            CGContextSetLineCap(context, kCGLineCapRound);
            CGContextSetLineWidth(context,20);
            CGContextSetBlendMode(context, kCGBlendModeClear);
            CGContextSetStrokeColorWithColor(context, [[UIColor clearColor] CGColor]);
            CGContextBeginPath(context);
            CGContextMoveToPoint(context, lastPoint.x, lastPoint.y);
            CGContextAddLineToPoint(context, currentPoint.x, currentPoint.y);
            CGContextStrokePath(context);
            CGContextFlush(context);
            if(flagActiveViewPage)
                self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
            else
                self.mainImage1.image = UIGraphicsGetImageFromCurrentImageContext();

            UIGraphicsEndImageContext();
            lastPoint = currentPoint;

        }
    });
    }

May this will Help u to solve ur problem.

Thanks