MKMapKit(九)：动态圆形DynamicCircleOverlay

Overlay的准备

根据文章[动态Overlay绘制][link01]提到的要点，我们需要一个有世界范围一半的Bounding来保证Circle在扩大的过程中不会变形

//头文件
@interface DynamicCircleOverly : MKShape <MKOverlay>

- (instancetype)initWithCoordinate:(CLLocationCoordinate2D)coordinate;

@end

//实现文件
@interface DynamicCircleOverly ()

@property (nonatomic, assign) CLLocationCoordinate2D center;
@property (nonatomic, assign) MKMapRect mapRect;

@end


@implementation DynamicCircleOverly


- (instancetype)initWithCoordinate:(CLLocationCoordinate2D)coordinate {
    self = [super init];
    if (self) {
        _center = coordinate;
        _mapRect = [self worldRectWithCenter:coordinate];

    }
    return self;
}

- (CLLocationCoordinate2D)coordinate {
    if(MKMapRectEqualToRect(_mapRect, MKMapRectNull)) {
        _mapRect = [self worldRectWithCenter:self.coordinate];
    }
    return _center;
}

- (MKMapRect)boundingMapRect {
    return _mapRect;
}

- (MKMapRect)worldRectWithCenter:(CLLocationCoordinate2D)coordinate {
    MKMapPoint center = MKMapPointForCoordinate(coordinate);
    double width = MKMapSizeWorld.width/2;
    double height = MKMapSizeWorld.height/2;
    MKMapPoint origin = MKMapPointMake(center.x - width/2, center.y - height/2);

    return MKMapRectMake(origin.x, origin.y, width , height);

}

@end

Render的准备

完成Render需要保证以下逻辑

1. 正确的圆形绘制方法
2. 在更新半径时调用 setNeedsDisplay 重新绘制

示例代码如下

//头文件
@interface DynamicCircleRender : MKOverlayRenderer

@property (nonatomic, readonly) CGFloat radius;

- (void)updateRadius:(CGFloat)radius;

@end

//实现文件
@implementation DynamicCircleRender


- (instancetype)initWithOverlay:(id<MKOverlay>)overlay {
    self = [super initWithOverlay: overlay];
    if (self) {
        _radius = 0;
    }
    return self;
}



- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {
    //1. Map计算 将CGFloat类型的半径换算成MKMapPoint的点数
    MKMapPoint mapPoint = MKMapPointForCoordinate(self.overlay.coordinate);
    double radiusAtLatitude = (_radius)*MKMapPointsPerMeterAtLatitude(self.overlay.coordinate.latitude);

    //2. Screen 将 MKMapView 换算成当前的ScreenView上的参数
    CGPoint center = [self pointForMapPoint:mapPoint];

    //3. Prepare Draw 绘制准备，决定绘制颜色和方法
    CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
    CGContextAddArc(context, center.x, center.y, radiusAtLatitude , 0,  2 * M_PI, 1);

    //4. Draw 进行绘制
    CGContextDrawPath(context, kCGPathFillStroke);
    UIGraphicsPopContext();

}


- (void)updateRadius:(CGFloat)radius {
    _radius = radius;
    // 调用刷新方法
    [self setNeedsDisplay];
}

@end

赏

请问老板还招人么(/ω＼)

支付宝

微信