CGContextBeginPath:无效上下文0x0

Question

图片我正在使用离子型/科尔多瓦地图插件开发一个地图应用程序，我想改变标记，所以我在ios平台上改变插件。我正在传递标记图标中的自定义属性，并绘制一个矩形以显示标记上的标题。从本地加载图像时，从circularScaleAndCropImage方法调用setIcon方法。

我得到了这个上下文错误，我不知道如何解决这个问题。

    `-(void)setIcon_:(GMSMarker *)marker iconProperty:(NSDictionary *)iconProperty
   pluginResult:(CDVPluginResult *)pluginResult
     callbackId:(NSString*)callbackId {

    if (self.mapCtrl.debuggable) {
        NSLog(@"---- setIcon_");
    }
    NSString *iconPath = nil;
    CGFloat width = 0;
    CGFloat height = 0;
    CGFloat anchorX = 0;
    CGFloat anchorY = 0;

    NSString *iconType = nil;
    NSString *borderColor = nil;
    NSString *ImageMarkerString = @"ImageMarker";
    NSString *markerLabel = nil;
    NSString *markerHeading = nil;
    // `url` property
    iconPath = [iconProperty valueForKey:@"url"];
    iconType = [iconProperty valueForKey:@"iconType"];
    //    NSLog(@"iconType = %@", iconType);
    borderColor = [iconProperty valueForKey:@"borderColor"];
    if(!borderColor){
        borderColor = @"#006600";
    }

    markerLabel =[iconProperty valueForKey:@"markerLabel"];
    if(!markerLabel){
        markerLabel= @"no_Label";
    }
    markerHeading =[iconProperty valueForKey:@"markerHeading"];
    if(!markerHeading){
        markerHeading = @"no_Heading";
    }

    // `size` property
    if ([iconProperty valueForKey:@"size"]) {
        NSDictionary *size = [iconProperty valueForKey:@"size"];
        width = [[size objectForKey:@"width"] floatValue];
        height = [[size objectForKey:@"height"] floatValue];
    }

    // `animation` property
    NSString *animationValue = nil;
    if ([iconProperty valueForKey:@"animation"]) {
        animationValue = [iconProperty valueForKey:@"animation"];
    }
    __block NSString *animation = animationValue;

    if (iconPath) {

        NSRange range = [iconPath rangeOfString:@"http"];
        if (range.location != 0) {
            /**
             * Load icon from file or Base64 encoded strings
             */
            Boolean isTextMode = true;

            UIImage *image;
            if ([iconPath rangeOfString:@"data:image/"].location != NSNotFound &&
                [iconPath rangeOfString:@";base64,"].location != NSNotFound) {

                /**
                 * Base64 icon
                 */
                isTextMode = false;
                NSArray *tmp = [iconPath componentsSeparatedByString:@","];

                NSData *decodedData;
#if !defined(__IPHONE_8_0)
                if ([PluginUtil isIOS7_OR_OVER]) {
                    decodedData = [NSData dataFromBase64String:tmp[1]];
                } else {
#if !defined(__IPHONE_7_0)
                    decodedData = [[NSData alloc] initWithBase64Encoding:(NSString *)tmp[1]];
#endif
                }
#else
                decodedData = [NSData dataFromBase64String:tmp[1]];
#endif
                image = [[UIImage alloc] initWithData:decodedData];
                if (width && height) {
                    image = [image resize:width height:height];
                }
                if([iconType isEqualToString:ImageMarkerString ]){
                    NSLog(@"ICON Marker Type Condition True 1");
                    CGRect newRect = CGRectMake(0, 0, width, height);
                    image = [self circularScaleAndCropImage:image frame:newRect color:borderColor label : markerLabel heading :markerHeading];
                }

                // The `anchor` property for the icon
                if ([iconProperty valueForKey:@"anchor"]) {
                    NSArray *points = [iconProperty valueForKey:@"anchor"];
                    anchorX = [[points objectAtIndex:0] floatValue] / image.size.width;
                    anchorY = [[points objectAtIndex:1] floatValue] / image.size.height;
                    marker.groundAnchor = CGPointMake(anchorX, anchorY);
                }

            } else {
                /**
                 * Load the icon from local path
                 */

                range = [iconPath rangeOfString:@"cdvfile://"];
                if (range.location != NSNotFound) {

                    iconPath = [PluginUtil getAbsolutePathFromCDVFilePath:self.webView cdvFilePath:iconPath];

                    if (iconPath == nil) {
                        if (self.mapCtrl.debuggable) {
                            NSLog(@"(debug)Can not convert '%@' to device full path.", iconPath);
                        }
                        [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
                        return;
                    }
                }


                range = [iconPath rangeOfString:@"://"];
                if (range.location == NSNotFound) {
                    range = [iconPath rangeOfString:@"www/"];
                    if (range.location == NSNotFound) {
                        iconPath = [NSString stringWithFormat:@"www/%@", iconPath];
                    }

                    range = [iconPath rangeOfString:@"/"];
                    if (range.location != 0) {
                      // Get the absolute path of the www folder.
                      // https://github.com/apache/cordova-plugin-file/blob/1e2593f42455aa78d7fff7400a834beb37a0683c/src/ios/CDVFile.m#L506
                      NSString *applicationDirectory = [[NSURL fileURLWithPath:[[NSBundle mainBundle] resourcePath]] absoluteString];
                      iconPath = [NSString stringWithFormat:@"%@%@", applicationDirectory, iconPath];
                    } else {
                      iconPath = [NSString stringWithFormat:@"file://%@", iconPath];
                    }
                }

                range = [iconPath rangeOfString:@"file://"];
                if (range.location != NSNotFound) {

                    #ifdef __CORDOVA_4_0_0
                        NSURL *fileURL = [NSURL URLWithString:iconPath];
                        NSURL *resolvedFileURL = [fileURL URLByResolvingSymlinksInPath];
                        iconPath = [resolvedFileURL path];
                    #else
                        iconPath = [iconPath stringByReplacingOccurrencesOfString:@"file://" withString:@""];
                    #endif

                    NSFileManager *fileManager = [NSFileManager defaultManager];
                    if (![fileManager fileExistsAtPath:iconPath]) {
                        if (self.mapCtrl.debuggable) {
                            NSLog(@"(debug)There is no file at '%@'.", iconPath);
                        }
                        [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
                        return;
                    }
                }

                image = [UIImage imageNamed:iconPath];

                if (width && height) {
                    image = [image resize:width height:height];
                }
            }
            if([iconType isEqualToString:ImageMarkerString ]){
                NSLog(@"ICON Marker Type Condition True 2");
                CGRect newRect = CGRectMake(0, 0, width, height);
                dispatch_async(dispatch_get_main_queue(), ^{[self circularScaleAndCropImage:image frame:newRect color:borderColor label : markerLabel heading :markerHeading];});

            }

            marker.icon = image;
            // The `anchor` property for the icon
            if ([iconProperty valueForKey:@"anchor"]) {
                NSArray *points = [iconProperty valueForKey:@"anchor"];
                anchorX = [[points objectAtIndex:0] floatValue] / image.size.width;
                anchorY = [[points objectAtIndex:1] floatValue] / image.size.height;
                marker.groundAnchor = CGPointMake(anchorX, anchorY);
            }

            // The `infoWindowAnchor` property
            if ([iconProperty valueForKey:@"infoWindowAnchor"]) {
                NSArray *points = [iconProperty valueForKey:@"infoWindowAnchor"];
                anchorX = [[points objectAtIndex:0] floatValue] / image.size.width;
                anchorY = [[points objectAtIndex:1] floatValue] / image.size.height;
                marker.infoWindowAnchor = CGPointMake(anchorX, anchorY);
            }


            // The `visible` property
            if (iconProperty[@"visible"]) {
                marker.map = self.mapCtrl.map;
            }

            if (animation) {
                // Do animation, then send the result
                [self setMarkerAnimation_:animation marker:marker pluginResult:pluginResult callbackId:callbackId];
            } else {
                // Send the result
                [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
            }
        } else {
            if (self.mapCtrl.debuggable) {
                NSLog(@"---- Load the icon from the internet");
            }
            /***
             * Load the icon from the internet
             */

            /*
             // download the image asynchronously
             R9HTTPRequest *request = [[R9HTTPRequest alloc] initWithURL:url];
             [request setHTTPMethod:@"GET"];
             [request setTimeoutInterval:5];
             [request setFailedHandler:^(NSError *error){}];
             */


            dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
            dispatch_async(queue, ^{

                NSURL *url = [NSURL URLWithString:iconPath];

                [self downloadImageWithURL:url completionBlock:^(BOOL succeeded, UIImage *image) {

                    if (!succeeded) {

                        // The `visible` property
                        if ([[iconProperty valueForKey:@"visible"] boolValue]) {
                            marker.map = self.mapCtrl.map;
                        }

                        [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
                        return;
                    }

                    if (width && height) {
                        image = [image resize:width height:height];
                    }

                    if([iconType isEqualToString:ImageMarkerString ]){
                        NSLog(@"ICON Marker Type Condition True 3");
                        CGRect newRect = CGRectMake(0, 0, width, height);
                        image = [self circularScaleAndCropImage:image frame:newRect color:borderColor label : markerLabel heading :markerHeading];
                    }
                    dispatch_async(dispatch_get_main_queue(), ^{
                        marker.icon = image;

                        // The `anchor` property for the icon
                        if ([iconProperty valueForKey:@"anchor"]) {
                            NSArray *points = [iconProperty valueForKey:@"anchor"];
                            CGFloat anchorX = [[points objectAtIndex:0] floatValue] / image.size.width;
                            CGFloat anchorY = [[points objectAtIndex:1] floatValue] / image.size.height;
                            marker.groundAnchor = CGPointMake(anchorX, anchorY);
                        }


                        // The `infoWindowAnchor` property
                        if ([iconProperty valueForKey:@"infoWindowAnchor"]) {
                            NSArray *points = [iconProperty valueForKey:@"infoWindowAnchor"];
                            CGFloat anchorX = [[points objectAtIndex:0] floatValue] / image.size.width;
                            CGFloat anchorY = [[points objectAtIndex:1] floatValue] / image.size.height;
                            marker.infoWindowAnchor = CGPointMake(anchorX, anchorY);
                        }

                        // The `visible` property
                        if ([[iconProperty valueForKey:@"visible"] boolValue]) {
                            marker.map = self.mapCtrl.map;
                        }


                        if (animation) {
                            // Do animation, then send the result
                            if (self.mapCtrl.debuggable) {
                                NSLog(@"---- do animation animation = %@", animation);
                            }
                            [self setMarkerAnimation_:animation marker:marker pluginResult:pluginResult callbackId:callbackId];
                        } else {
                            // Send the result
                            if (self.mapCtrl.debuggable) {
                                NSLog(@"---- no marker animation");
                            }
                            [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
                        }

                    });


                }];

            });


        }
    } else if ([iconProperty valueForKey:@"iconColor"]) {
        UIColor *iconColor = [iconProperty valueForKey:@"iconColor"];
        marker.icon = [GMSMarker markerImageWithColor:iconColor];

        // The `visible` property
        if ([[iconProperty valueForKey:@"visible"] boolValue]) {
            marker.map = self.mapCtrl.map;
        }

        if (animation) {
            // Do animation, then send the result
            [self setMarkerAnimation_:animation marker:marker pluginResult:pluginResult callbackId:callbackId];
        } else {
            // Send the result
            [self.commandDelegate sendPluginResult:pluginResult callbackId:callbackId];
        }

    }

}
`
- (UIImage*)circularScaleAndCropImage:(UIImage*)image frame:(CGRect)frame color:(NSString *)color label :(NSString *)label heading :(NSString *)heading{
    // This function returns a newImage, based on image, that has been:
    // - scaled to fit in (CGRect) rect
    // - and cropped within a circle of radius: rectWidth/2

    NSLog(@"function called");
    NSString *htmlTemplate =
    @"<html>\n"
    "<head>\n"
    "<style type=\"text/css\">\n"
    "body span{\n"
    "font-family: HelveticaNeue;\n"
    "border-radius : 3px;\n"
    "font-size: 11px;\n"
    "font-weight: normal;\n"
    "text-align: center;\n"
    "}\n"
    "</style>\n"
    "</head>\n"
    "<body>\n"
    "%@\n"
    "</body>\n"
    "</html>";
    //Create the bitmap graphics context
    NSString *noLabel = @"no_Label";
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(frame.size.width, frame.size.width), NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();

    NSLog(@"function called");
    //Get the width and heights
    CGFloat imageWidth = image.size.width;
    CGFloat imageHeight = image.size.height;
    CGFloat rectWidth = frame.size.width;

    //Calculate the centre of the circle
    CGFloat imageCentreX = imageWidth/2;

    //Calculate the radius of circle
    CGFloat radius = rectWidth/2;

    //Create circle
    CGContextBeginPath (context);
    CGContextAddArc (context, imageCentreX, imageCentreX, radius-3, 0, 2*M_PI, 0);
    CGContextClosePath (context);

    //Crop circle
    CGContextClip (context);

    //Create rectangle for image and draw in it.
    CGRect NewMmyRect = CGRectMake(0,0,  imageWidth, imageHeight);
    [[self colorFromHexString: color] setFill];  // changes are here
    UIRectFill(NewMmyRect);               // and here

    if(label != noLabel){
        NSString * htmlString = label;
        NSAttributedString * attrStr = [[NSAttributedString alloc] initWithData:[[NSString stringWithFormat:htmlTemplate, htmlString]  dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil];

        UILabel * myLabel = [[UILabel alloc] initWithFrame:NewMmyRect];
        myLabel.attributedText = attrStr;
        myLabel.numberOfLines = 0;
        [myLabel sizeToFit];
        [myLabel drawTextInRect:NewMmyRect];
    } else{
        [image drawInRect:NewMmyRect];
    }

    //Convert context into an image and remoove the context
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    //Create a new Image context
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(frame.size.width*2, (imageWidth-2)*1.5-8+25), NO, 0.0);
    CGContextRef context2 = UIGraphicsGetCurrentContext();
    //Create a rectange around the circled image and draw stroke on it.
    float frameWidth =frame.size.width*2;
    float newRectWidth =rectWidth-5;
    CGRect NewMmyRect2 = CGRectMake((frameWidth/2-newRectWidth/2),25,  rectWidth-5, rectWidth-5);
    [newImage drawInRect:NewMmyRect2];


    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:NewMmyRect2 cornerRadius:imageWidth];
    bezierPath.lineWidth =4;
    CGContextSetStrokeColorWithColor(context2,  [self colorFromHexString: color].CGColor);
    [bezierPath stroke];


    //Create a triangle for bottom pin
    CGContextBeginPath(context2);

    float fithpart =frameWidth/6;
    CGContextMoveToPoint(context2, fithpart*2.5, newRectWidth+25);
    CGContextAddLineToPoint(context2,fithpart*3.5, newRectWidth+25);
    CGContextAddLineToPoint(context2,(frameWidth/2), newRectWidth+25+12);

    CGContextClosePath(context2);



    CGContextSetFillColorWithColor(context2, [self colorFromHexString:color].CGColor);
    CGContextFillPath(context2);
    NSString *noLabel2 = @"no_Heading";
    if(heading != noLabel2){


        CGRect rect1 = NewMmyRect;
        CGRect rect2 = CGRectMake(0, 0, frame.size.width*2, 22);
        UIBezierPath *bezierCorner = [UIBezierPath bezierPathWithRoundedRect:rect2 cornerRadius:3.00];
        CGContextSetFillColorWithColor(context2,  [self colorFromHexString: color].CGColor);
        [bezierCorner fill];
        NSString * htmlStringHeading = heading;
        NSAttributedString * attrStr2 = [[NSAttributedString alloc] initWithData:[[NSString stringWithFormat:htmlTemplate, htmlStringHeading] dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil];
        //UIRectFill(rect2);
        UILabel * myLabel2 = [[UILabel alloc] initWithFrame:rect2];
        myLabel2.attributedText = attrStr2;
        myLabel2.numberOfLines = 0;
        [myLabel2 sizeToFit];
        [myLabel2 drawTextInRect:rect2];
        CGRectUnion(rect2, rect1);
    }

    UIImage *newImage2 = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage2;
} 

请看这张图，并建议我解决这个问题的方法。

Answer 1

终于明白了。

这是一个问题的宽度和高度，我是传递给矩形。宽度和高度值为0。

这就是为什么我会犯这个错误。

Answer 2

我认为主要的问题就在这里，您想要异步下载映像。

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
    NSURL *url = [NSURL URLWithString:iconPath];
    [self downloadImageWithURL:url completionBlock:^(BOOL succeeded, UIImage *image) {

    ...
});

这种方法很好，基本问题是:返回的映像不应在主线程中处理，而处理功能实际上需要在主线程中执行。

这也是为什么稍后在代码块中要在主线程中执行更改的原因：

dispatch_async(dispatch_get_main_queue(), ^{
    marker.icon = image;
    ...
});

因此，您必须做的是:在主线程中执行图像处理--在您的情况下，您甚至可以使用以下调度器：

因此，与其：

if([iconType isEqualToString:ImageMarkerString ]){
    NSLog(@"ICON Marker Type Condition True 3");
    CGRect newRect = CGRectMake(0, 0, width, height);
    image = [self circularScaleAndCropImage:image frame:newRect color:borderColor label : markerLabel heading :markerHeading];
}
dispatch_async(dispatch_get_main_queue(), ^{
    marker.icon = image;
    ...
});

将处理移到主线程中，因此最终看起来如下：

dispatch_async(dispatch_get_main_queue(), ^{
    if([iconType isEqualToString:ImageMarkerString ]){
        NSLog(@"ICON Marker Type Condition True 3");
        CGRect newRect = CGRectMake(0, 0, width, height);
        image = [self circularScaleAndCropImage:image frame:newRect color:borderColor label : markerLabel heading :markerHeading];
    }
    marker.icon = image;

    ...
});

有关如何使用调度程序的其他信息，请参见以下内容：https://developer.apple.com/library/content/documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html

下面是有关上下文的一些die注释，在其中应该执行操作：https://developer.apple.com/library/content/documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html