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POhow do I redraw overlays on a map
 

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  1. POhow do I redraw overlays on a map
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    <p>I have a map that creates paths and stores them in a DB. When the app is reloaded any saved paths are loaded again as a overlay It works fine until I zoom in and I see that they don't resize properly. How can I force a redraw to correct the size. I included a screen shot of what I'm seeing.</p> <p><img src="https://i.stack.imgur.com/6hTyt.jpg" alt="enter image description here"></p> <p>Here is a sample of my code. It draws subpaths for each point. Similar to a breadcrump following the users location. It's in a custom overlap class and called in </p> <pre><code>-(void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context { for (int io=0;io&lt;OverlayList.count;io++){ CrumbPath *crumbs = [OverlayList objectAtIndex:io]; NSMutableArray *colors = [NSMutableArray arrayWithCapacity:2]; UIColor *color = [UIColor redColor]; int speedcolor; UIColor *currentColor = [UIColor colorWithRed:255/255.0f green:256/255.0f blue:0/255.0f alpha:1.0f]; UIColor *NewcurrentColor = [UIColor colorWithRed:255/255.0f green:256/255.0f blue:0/255.0f alpha:1.0f]; [colors addObject:(id)[color CGColor]]; for (int i=0;i&lt;crumbs.pointCount;i++){ NSInteger CurrentSpeed=crumbs.pointSpeed[i]; speedcolor=255-((int)CurrentSpeed*3); if (speedcolor&lt;2){ speedcolor=1; } CGMutablePathRef subpath = CGPathCreateMutable(); CGPoint point = [self pointForMapPoint:crumbs.points[i]]; if (i==0){ CGPathMoveToPoint(subpath, nil, point.x, point.y); CGPathRelease(subpath); } else { CGPoint prevPoint = [self pointForMapPoint:crumbs.points[i-1]]; CGPathMoveToPoint(subpath, nil, prevPoint.x, prevPoint.y); CGPathAddLineToPoint(subpath, nil, point.x, point.y); CGFloat lineWidth = MKRoadWidthAtZoomScale(zoomScale); CGFloat gradientLocation[2] = {0,1}; CGContextSaveGState(context); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGPoint gradientStart = prevPoint; CGPoint gradientEnd = point; CGGradientRef gradient; NewcurrentColor = [UIColor colorWithRed:255/255.0f green:speedcolor/255.0f blue:0/255.0f alpha:1.0f]; NSMutableArray *colors = [NSMutableArray arrayWithCapacity:2]; UIColor *color; [colors addObject:(id)[currentColor CGColor]]; color = NewcurrentColor; [colors addObject:(id)[color CGColor]]; gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)colors, gradientLocation); CGPathRef pathToFill = CGPathCreateCopyByStrokingPath(subpath, NULL, lineWidth, kCGLineCapRound, kCGLineJoinBevel, 0); CGContextAddPath(context, pathToFill); //NSLog(@"%f",lineWidth); CGContextClip(context);//&lt;--clip your context after you SAVE it, important! CGContextDrawLinearGradient(context, gradient, gradientStart, gradientEnd, kCGGradientDrawsBeforeStartLocation); CGContextRestoreGState(context);//&lt;--Don't forget to restore your context. currentColor = NewcurrentColor; CGGradientRelease(gradient); CGPathRelease(pathToFill); CGColorSpaceRelease(colorSpace); CGPathRelease(subpath); } } } </code></pre>
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    1. COWe could use a bit more information on how the path is drawn in the first place. It would be best if you show some drawing-code.
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      1. USSti
    2. COGood point. I edited my original.
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      1. POhow do I redraw overlays on a map
      1. USjdross
    3. COSo you're not using the MKPolyline? If you did that the path would get redrawn by the map view every time and be smooth at every step.
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      1. USCraig
 

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