在地图视图上绘制MKCircle

Question

我需要画一个圆来显示我所绘制的点周围的距离。

我应该在哪里实现这两行代码以使其工作？我试着把它放到viewWillAppear:中，但是圆圈没有出现。

[self addCircle:_coordinate];
[self addCircleWithRadius:5.5 addCircleWithCoordinate:_coordinate];

- (void)addCircle: (CLLocationCoordinate2D)coordinate
{
    // draw the radius circle for the marker

    double radius = 2000.0;
    MKCircle *circle = [MKCircle circleWithCenterCoordinate:coordinate radius:radius];
    [circle setTitle:@"background"];
    [_mapView addOverlay:circle];

    MKCircle *circleLine = [MKCircle circleWithCenterCoordinate:coordinate radius:radius];
    [circleLine setTitle:@"line"];
    [_mapView addOverlay:circleLine];
}

- (void)addCircleWithRadius:(double)radius addCircleWithCoordinate: (CLLocationCoordinate2D) coordinate
{

    MKCircle *circle = [MKCircle circleWithCenterCoordinate:coordinate radius:radius];
    [circle setTitle:@"background"];
    [_mapView addOverlay:circle];

    MKCircle *circleLine = [MKCircle circleWithCenterCoordinate:coordinate radius:radius];
    [circleLine setTitle:@"line"];
    [_mapView addOverlay:circleLine];
}

- (void)sliderChanged:(UISlider*)sender
{
    [_mapView removeOverlays:[_mapView overlays]];

    double radius = (sender.value * 100);
    CLLocationCoordinate2D coordinate = self.coordinate;

    [self addCircleWithRadius:radius addCircleWithCoordinate:coordinate];
}

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay{
    MKCircle *circle = overlay;
    MKCircleView *circleView = [[[MKCircleView alloc] initWithCircle:overlay] autorelease];

    if ([circle.title isEqualToString:@"background"])
    {
        //circleView.fillColor = UIColorFromRGB(0x598DD3);
        circleView.alpha = 0.25;
    }
    else
    {
        //circleView.strokeColor = UIColorFromRGB(0x5C8AC7);
        circleView.lineWidth = 2.0;
    }

    return circleView;
}

Answer 1

虽然您可以尝试viewDidAppear而不是viewWillAppear，但我认为它应该已经在这方面起作用了。我认为您有其他错误，您应该通过调试器找到它。查查通常的嫌疑人：

• 设置填充颜色。使其不透明，obvious.
• _mapView可能在运行时为零或僵尸。(或者不在xib中映射)
• 的坐标或半径可能与您预期的不同。检查debugger.
• Everything中的实际坐标值可能是正确的，除非坐标不在地图的缩放区域。