Ios 核心绘图如何在绘图空间中将触摸感应点转换为点？

我不熟悉核心情节。我正试图计算距离以下代码中感应到触摸的坐标最近的数据点：

-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceDownEvent:(id)event atPoint:(CGPoint)point
{
    NSLog(@"touch sensed");
    NSLog(@"points: %f, %f",point.x,point.y);
    [self.distances removeAllObjects];

    CPTGraph *graph = self.hostView.hostedGraph;
    if (symbolTextAnnotation) {
        [graph.plotAreaFrame.plotArea removeAnnotation:symbolTextAnnotation];
        symbolTextAnnotation = nil;
    }
    CPTMutableTextStyle *hitAnnotationTextStyle = [CPTMutableTextStyle textStyle];
    hitAnnotationTextStyle.color    = [CPTColor whiteColor];
    hitAnnotationTextStyle.fontSize = 16.0;
    hitAnnotationTextStyle.fontName = @"Helvetica-Bold";
    for(int i=0;i<[self.allX count];i++){
        //NSLog(@"-->all points: %@, %@", [self.allX objectAtIndex:i],[self.allY objectAtIndex:i]);
        NSLog(@"-->all points: %f, %f", [[self.allX objectAtIndex:i] floatValue],[[self.allY objectAtIndex:i] floatValue]);
        CGFloat xDist = (point.x - [[self.allX objectAtIndex:i] floatValue]);
        CGFloat yDist = (point.y - [[self.allY objectAtIndex:i] floatValue]);
        NSLog(@"-->all distances: %f, %f", xDist,yDist);
        CGFloat distance = sqrt((xDist * xDist) + (yDist * yDist));
        NSNumber *distanceNum = [NSNumber numberWithFloat:distance];
        NSLog(@"-->total distance: %@", distanceNum);
        [self.distances addObject:distanceNum];
    }

    for(int i=0;i<[self.distances count];i++){
        NSLog(@"calculated distances: %@",[self.distances objectAtIndex:i]);
    }

    NSNumber *minDistance = [self.distances valueForKeyPath:@"@min.doubleValue"];
    NSLog(@"min distance: %@", minDistance);
    int index=[self.distances indexOfObject:minDistance];
    NSLog(@"cloest point: %@,%@",[self.allX objectAtIndex:index],[self.allY objectAtIndex:index]);

    NSArray *anchorPoint = @[[self.allX objectAtIndex:index], [self.allY objectAtIndex:index] ];

    CPTTextLayer *textLayer = [[CPTTextLayer alloc] initWithText:@"LABEL" style:hitAnnotationTextStyle] ;
    symbolTextAnnotation              = [[CPTPlotSpaceAnnotation alloc] initWithPlotSpace:graph.defaultPlotSpace anchorPlotPoint:anchorPoint];
    symbolTextAnnotation.contentLayer = textLayer;
    symbolTextAnnotation.displacement = CGPointMake(0.0, 20.0);
    [graph.plotAreaFrame.plotArea addAnnotation:symbolTextAnnotation];

    return 1;
}

-（BOOL）绘图空间：（CPTPlotSpace*）空间应与指针设备DownEvent:（id）事件在点：（CGPoint）点
{
NSLog（“触摸感应”）；
NSLog（@“点：%f，%f”，点x，点y）；
[self.removeAllObjects]；
CPTGraph*graph=self.hostView.hostdGraph；
if（symbolTextAnnotation）{
[graph.plotAreaFrame.plotArea removeAnnotation:symbolTextAnnotation]；
symbolTextAnnotation=nil；
}
CPTMutableTextStyle*hitAnnotationTextStyle=[CPTMutableTextStyle]；
hitAnnotationTextStyle.color=[CPTColor whiteColor]；
hitAnnotationTextStyle.fontSize=16.0；
hitAnnotationTextStyle.fontName=@“Helvetica Bold”；
对于（int i=0；i使用绘图空间（作为此方法的参数传递）在数据坐标和绘图区域视图坐标之间进行转换

使用以下方法之一从
事件中提取触摸坐标
，并将其转换为数据坐标

-(void)plotPoint:(NSDecimal *)plotPoint numberOfCoordinates:(NSUInteger)count forEvent:(CPTNativeEvent *)event;
-(void)doublePrecisionPlotPoint:(double *)plotPoint numberOfCoordinates:(NSUInteger)count forEvent:(CPTNativeEvent *)event;

或者，使用
-plotAreaViewPointForEvent:
方法从事件中提取触点的视图坐标，并使用以下方法之一将数据坐标转换为视图坐标，并计算该坐标系中的距离：

-(CGPoint)plotAreaViewPointForPlotPoint:(NSDecimal *)plotPoint numberOfCoordinates:(NSUInteger)count;
-(CGPoint)plotAreaViewPointForDoublePrecisionPlotPoint:(double *)plotPoint numberOfCoordinates:(NSUInteger)count;

我使用了以下代码，与您所说的类似：NSDecimal plotPoint[2]；[space plotPoint:plotPoint FORPLOTAREA VIEW:point]；，但没有为plotPoint:PLOTAREA VIEWPOINT声明@接口，即使您使用的是哪一版本的核心绘图？自版本1.1（1.5.1是最新版本）起，“事件”方法就一直存在。