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我想在地图视图上画一个有洞的圆圈（比如甜甜圈）。我的代码在这里。

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CG    ContextRef)context {

WPCircleOverlay * circleOverlay = self.overlay;

CGPoint centerPoint = [self pointForMapPoint:MKMapPointForCoordinate(circleOverlay.coordinate)];

CGFloat innerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.innerRadius;
CGFloat outerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.outerRadius;
CGMutablePathRef path = CGPathCreateMutable();

//CGPathMoveToPoint(path, ...);
CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, outerRadius, 0, 2 * M_PI, true);
CGPathCloseSubpath(path);

// Add the inner arc to the path (later used to substract the inner area)
CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, innerRadius, 0, 2 * M_PI, true);
CGPathCloseSubpath(path);

// Add the path to the context
CGContextAddPath(context, path);

CGContextSetFillColorWithColor(context, self.fillColor.CGColor);
CGContextEOFillPath(context);

CGPathRelease(path);

它在模拟器中运行良好，但在设备上却不行。

在设备上，外圈用颜色填充，内圈没有被剪裁。如何修改我的代码以在设备上正常工作？

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1 回答 1

2

我通过使用 CGContextAddEllipseInRect 方法而不是 CGContextAddArc 来修复它。

WPCircleOverlay * circleOverlay = self.overlay;

CGRect rectForMapRect = [self rectForMapRect:mapRect];
CGPoint centerPoint = [self pointForMapPoint:MKMapPointForCoordinate(circleOverlay.coordinate)];

CGFloat innerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.innerRadius;
CGFloat outerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.outerRadius;

CGRect innerRect = CGRectMake(centerPoint.x - innerRadius, centerPoint.y - innerRadius, innerRadius * 2.0, innerRadius * 2.0);
CGRect outerRect = CGRectMake(centerPoint.x - outerRadius, centerPoint.y - outerRadius, outerRadius * 2.0, outerRadius * 2.0);

if (CGRectIntersectsRect(rectForMapRect, outerRect)) {

    CGContextAddRect(context, rectForMapRect);

    CGContextSaveGState(context);
    CGContextClip(context);

    CGContextAddEllipseInRect(context, outerRect);
    CGContextAddEllipseInRect(context, innerRect);

    CGContextSaveGState(context);
    CGContextEOClip(context);

    UIColor * color = [self.fillColor copy];
    CGContextSetFillColorWithColor(context, color.CGColor);
    CGContextFillRect(context, outerRect);

    CGContextRestoreGState(context);
    CGContextRestoreGState(context);

    UIGraphicsPopContext();
}
于 2014-02-20T16:14:09.483 回答