以像素为单位检测 CLLocationCoordinate2D 附近的触摸

Question

我在GMSMapView上有几个GMSMarker，它们都是可拖动的，所以当我长按它们时，我可以在地图上移动它们。但是，我在 GMSMapView 上也有一个长按操作，它添加了一个标记。

- (void)mapView:(GMSMapView *)mapView didBeginDraggingMarker:(GMSMarker *)marker {
    self.moving = YES;
}
- (void)mapView:(GMSMapView *)mapView didEndDraggingMarker:(GMSMarker *)marker {
    self.moving = NO;
}
- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
    if (self.moving) {
        return;
    }
    [self addMarkerAtCoordinate:coordinate];
}

现在的问题是，有时用户会犯错，他没有移动标记，而是添加了一个新标记。因此，我想在标记周围添加小区域，用户无法在其中添加新标记。我想过这样的事情：

- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
    CGFloat zoomFactor = 35.f - self.mapView.camera.zoom;
    CLLocation *location = [[CLLocation alloc] initWithLatitude:coordinate.latitude longitude:coordinate.longitude];
    for (GMSMarker *marker in self.markers) {
        CLLocation *sectorLocation = [[CLLocation alloc] initWithLatitude:marker.position.latitude longitude:marker.position.longitude];
        if ([location distanceFromLocation:sectorLocation] < zoomFactor) {
            return;
        }
    }
}

但我当然不喜欢这个解决方案，因为区域会随着缩放比例的变化而变化。我想要像标记周围手指宽度的东西被禁止长按。这个距离怎么计算？

Answer 1

在 GMSProjection GMSMapView 对象上使用方法 pointForCoordinate: 可以很容易地将坐标转换为视图中的位置。

- (void)mapView:(GMSMapView *)mapView didLongPressAtCoordinate:(CLLocationCoordinate2D)coordinate {
    CGPoint longpressPoint = [mapView.projection pointForCoordinate:coordinate];
    for (GMSMarker *marker in self.markers) {
        CLLocationCoordinate2D markerCoordinate = marker.position;
        CGPoint sectorPoint = [mapView.projection pointForCoordinate:markerCoordinate];
        if (fabsf(longpressPoint.x - markerCoordinate.x) < 30.f && fabsf(longpressPoint.y - markerCoordinate.y) < 30.f) { // 30.f ofc should be defined as constant
            // handle situation when touchpoint is too close to marker
        }
    }
}

以像素为单位检测 CLLocationCoordinate2D 附近的触摸

Detect touch nearby to CLLocationCoordinate2D in pixels

ios

objective-c

google-maps

google-maps-api-3