iOS – MKOverlayView自定义视图矩形填充工程，但线绘制不
新的地图叠加，但这是一个非常奇怪的问题。
我将mapView.visibleMapRect传递给我的覆盖实现，并将其作为boundingMapRect返回，这对于现在很好 – 只是试图在整个地图上绘制一条直线。
我的drawMapRect被调用，并在下面的代码 – 部分透明的绿色矩形绘制，但行不是。 我已经validation了uiview子类的drawRect中的绘图代码，所以我知道它绘制了一些东西:-)
我相信我一定会错过一些简单的东西，但我看不到它:-)
抛出我的是，visibleMapRect在转换为CGRect时有非常奇怪的坐标 – 它们看起来不像我的屏幕坐标 – 这对我来说似乎是问题的根源。
任何帮助将不胜感激：
drawMapRect被多次调用，我附加下面的输出。
谢谢，鲍勃
ViewController设置代码：
CLLocationCoordinate2D center; center.latitude = 29.46; center.longitude = -98.30; MKCoordinateRegion region; MKCoordinateSpan span; span.latitudeDelta = 0.2; span.longitudeDelta = 0.2; region.center = center; region.span = span; self.mapView.region = region; MyOverlay *myoverlay = [[MyOverlay alloc] initWithCoordinate: center andBoundingRect: self.mapView.visibleMapRect]; [self.mapView addOverlay:myoverlay]; MyOverlay代码：
@implementation MyOverlay @synthesize coordinate; @synthesize boundingMapRect; - (id) initWithCoordinate: (CLLocationCoordinate2D) coord andBoundingRect: (MKMapRect) bRect { if ((self = [super init])) { //customize here coordinate = coord; boundingMapRect = bRect; } return self; }
MyOverlayView绘图代码
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context { CGRect theRect = [self rectForMapRect:mapRect]; NSLog(@"in drawMapRect ...theRect is %f, %f, size of %fx %f", theRect.origin.x, theRect.origin.y, theRect.size.width, theRect.size.height); CGContextSetAlpha(context, 1.0); CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor); CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y); CGContextAddLineToPoint(context, theRect.size.width, theRect.size.width); CGContextSetAlpha(context, .25); CGContextSetFillColorWithColor(context, [UIColor greenColor].CGColor); CGContextFillRect(context, theRect); }
产量
2011-05-16 11:25:18.037 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.038 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.042 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.044 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.046 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.048 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.052 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.054 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.056 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.057 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.059 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.061 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.063 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.064 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 323584.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.066 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.068 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.070 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.072 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 585728.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.074 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.075 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, 37888.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.082 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 61440.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.082 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.085 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 61440.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.087 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.089 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, -224256.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.099 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.102 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, 300032.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.106 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 323584.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.109 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -200704.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.111 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -200704.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.116 coolOverlayTest[71661:760b] in drawMapRect ...theRect is 585728.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.119 coolOverlayTest[71661:7903] in drawMapRect ...theRect is 585728.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.124 coolOverlayTest[71661:7903] in drawMapRect ...theRect is -462848.000000, -486400.000000, size of 262144.000000 x 262144.000000 2011-05-16 11:25:18.126 coolOverlayTest[71661:760b] in drawMapRect ...theRect is -462848.000000, -486400.000000, size of 262144.000000 x 262144.000000
有一件事要考虑的是，出于性能的原因， drawMapRect:在多个线程上被调用。 这就解释了为什么你会看到drawMapRect:多次调用。 此外，此方法的mapRectinput不一定等于可见的mapView.visibleMapRect 。 实际上mapRect通常是mapRect的一小部分，不同的线程渲染mapView.visibleMapRect不同区域。 因此，仅仅因为mapView.visibleMapRect包含一个点，并不意味着它包含在传递给drawMapRect所有调用的mapRect 。
问题在于设置线宽。 在你的例子中，宽度没有设置。 如果你仍然想解决这个问题，看看这里自定义MKOverlayView线宽 。
您在对CGContextAddLineToPoint的调用中有错误的坐标。 你有：
CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y); CGContextAddLineToPoint(context, theRect.size.width, theRect.size.width);
但应该是：
CGContextMoveToPoint(context, theRect.origin.x, theRect.origin.y); CGContextAddLineToPoint(context, theRect.origin.x + theRect.size.width, theRect.origin.y + theRect.size.height);
至less如果你希望在你的矩形对angular线画一条线。
另外像上面提到的Ludvik Polak，你可能也需要使用类似的方法设置线宽：
CGContextSetLineWidth(context, MKRoadWidthAtZoomScale(zoomScale));