Coregraphics在iPad上造成很大的滞后? [英] Coregraphics causing big lag on iPad?

问题描述

 UIGraphicsBeginImageContext(self.view.bounds.size);
        [currentStrokeImageView.image drawInRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeNormal);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), dWidth);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, 1.0f);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), pointA.x, pointA.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), pointB.x, pointB.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        currentStrokeImageView.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

由于某些原因，这在iphone/ipod上绝对没有滞后，但是在iPad上，它们在绘制时是相当大的滞后.我上面使用的代码是否有解决此问题的建议?

For some reason this runs with absolutely no lag on the iphone/ipod but on the iPad their is a significant lag while drawing. The code I use is above, any suggestions to fix this?

推荐答案

之所以如此冗长，是因为您正在touchesMoved:withEvent:中执行此操作.接收到触摸事件时，可以多次(很明显)调用此方法.因为绘制到图形上下文可能是一项资源密集型操作，所以我建议不执行您在此处所做的所有事情.我将尽可能地将您正在执行的渲染推迟到touchesBegin和touchesEnd方法.如果这不可能，那么只有在运动中达到某个增量后，例如，每个2.0f点，您才可以执行这些操作.

The reason why this is so laggy is because you are doing it in the touchesMoved:withEvent:. This method can be called many, many times (obviously) while touch events are received. Because drawing to a graphics context can be a resource intensive operation, I would recommend not doing all the things you are doing there. I would, as much as possible, defer the rendering you are doing to the touchesBegin and touchesEnd methods. If that is not possible, perhaps you could only preform these operations once a certain delta has been reached in the movements, for example, every 2.0f points.

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