在我的应用程序中,我有一个CoreGraphics图像绘制模块。该应用程序在CGContextAddPath()函数调用中随机崩溃。路径是使用CGPathCreateMutable()函数调用创建的CGPathRef对象。示例代码如下:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
if (touching) return;
//start a new path
path = CGPathCreateMutable();
//set the path's starting point
UITouch *touch = (UITouch *)[touches anyObject];
CGPathMoveToPoint(path, NULL, [touch locationInView:m_view].x, [touch locationInView:m_view].y);
touching = YES;
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
if (touching){
//get the current location of the touch event
UITouch *theTouch = (UITouch *)[touches anyObject];
pathPoint = [theTouch locationInView:m_view];
CGPathAddLineToPoint(path, NULL, pathPoint.x, pathPoint.y);
[canvasLayer setNeedsDisplay];
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if (!touching) return;
//create a new image context
UIGraphicsBeginImageContext(CGSizeMake(backgroundLayer.bounds.size.width, backgroundLayer.bounds.size.height));
//grab a reference to the new image context
CGContextRef ctx = UIGraphicsGetCurrentContext();
//push the image context to the top of the drawing stack
UIGraphicsPushContext(ctx);
//set the blend mode to prevent white pixels from
//covering up the lines that have already been drawn
CGContextSetBlendMode(ctx, kCGBlendModeDarken);
if (cacheImage != nil) {
//draw the cached state of the image to the image context and release it
[cacheImage drawInRect:CGRectMake(0, 0, backgroundLayer.bounds.size.width, backgroundLayer.bounds.size.height)];
}
//blend the drawing layer into the image context
[canvasLayer drawInContext:ctx];
//we're done drawing to the image context
UIGraphicsPopContext();
//store the image context so we can add to it again later
cacheImage = UIGraphicsGetImageFromCurrentImageContext();
//we're finished with the image context altogether
UIGraphicsEndImageContext();
touching = NO;
//release the path
CGPathRelease(path);
//update the background layer (we'll need to draw the cached image to the background)
[backgroundLayer setNeedsDisplay];
}
- (void)drawLayer:(CATiledLayer *)layer inContext:(CGContextRef)ctx {
//this method is handling multiple layers, so first
//determine which layer we're drawing to
if (layer == canvasLayer) {
if (!touching) return;
//add the path to the context
CGContextAddPath(ctx, path); /***Exception points to this line***/
//set a line width and draw the path
CGContextSetLineWidth(ctx, 6.0f);//---thikness of line
CGContextStrokePath(ctx);
}
else if (layer == backgroundLayer) {
//remember the current state of the context
CGContextSaveGState(ctx);
//the cached image coordinate system is upside down, so do a backflip
CGContextTranslateCTM(ctx, 0, backgroundLayer.bounds.size.height);
CGContextScaleCTM(ctx, 1.0, -1.0);
//draw the image
CGImageRef ref = cacheImage.CGImage;
CGContextDrawImage(ctx, backgroundLayer.bounds, ref);
//restore the context to its pre-flipped state
CGContextRestoreGState(ctx);
}
}
从设备获得的诊断崩溃报告显示:
Exception Type: EXC_BAD_ACCESS (SIGBUS)
Exception Subtype: KERN_PROTECTION_FAILURE at 0x090d3330
Triggered by Thread: 13
Thread 13 name: Dispatch queue: com.apple.root.default-qos
Thread 13 Crashed:
0 ??? 0x090d3330 0 + 151860016
1 CoreGraphics 0x22886b6c 0x22874000 + 76652
2 CoreGraphics 0x228a036e 0x22874000 + 181102
3 MyApplication 0x001c8062 0xb6000 + 1122402
4 QuartzCore 0x256d08fc 0x25695000 + 243964
5 QuartzCore 0x257a9e86 0x25695000 + 1134214
6 QuartzCore 0x256fdd14 0x25695000 + 429332
7 libdispatch.dylib 0x30f99866 0x30f8b000 + 59494
8 libdispatch.dylib 0x30f9a89e 0x30f8b000 + 63646
9 libsystem_pthread.dylib 0x3110eda6 0x3110e000 + 3494
10 libsystem_pthread.dylib 0x3110eaf8 0x3110e000 + 2808
当我在崩溃报告中符号化内存地址时,异常指向CGContextAddPath(ctx,path);。是否由使用CGPathRelease(path);显式释放路径引起的?如果我注释了释放功能,则应用程序不会崩溃,但是会导致内存泄漏吗?
最佳答案
您可以在touchEnded中破坏路径,但是之后可能会调用drawLayer。
关于ios - iOS 8.3-CoreGraphics图像绘图中的EXC_BAD_ACCESS,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/29895303/