Question

我有以下代码来计算MKCoordinateRegion以显示包含两个定义点的地图。问题是当经度超过180度或-180度时，它不起作用。

CLLocationCoordinate2D tempPoint1 = CLLocationCoordinate2DMake(startLat,startLong);
CLLocationCoordinate2D tempPoint2 = CLLocationCoordinate2DMake(nextLat,nextLong);

if (lineType == 1) {
    [self createGreatCircleMKPolylineFromPoint: tempPoint1 toPoint: tempPoint2 forMapView:mapView];
}
else  {
    CLLocationCoordinate2D *coords = malloc(sizeof(CLLocationCoordinate2D) * 2);
    coords[0] = tempPoint1;
    coords[1] = tempPoint2;

    MKPolyline *polyline = [MKPolyline polylineWithCoordinates:coords count:2];
    free(coords);
    [mapView addOverlay:polyline];

}

double lon1 = tempPoint1.longitude * M_PI / 180;
double lon2 = tempPoint2.longitude * M_PI / 180;

double lat1 = tempPoint1.latitude * M_PI / 180;
double lat2 = tempPoint2.latitude * M_PI / 180;

double dLon = lon2 - lon1;

double x = cos(lat2) * cos(dLon);
double y = cos(lat2) * sin(dLon);

double lat3 = atan2( sin(lat1) + sin(lat2), sqrt((cos(lat1) + x) * (cos(lat1) + x) + y * y) );
double lon3 = lon1 + atan2(y, cos(lat1) + x);

CLLocationCoordinate2D center;

center.latitude  = lat3 * 180 / M_PI;
center.longitude = lon3 * 180 / M_PI;


MKCoordinateSpan locationSpan;
locationSpan.latitudeDelta = fabs(tempPoint1.latitude - tempPoint2.latitude) * 1.2;
locationSpan.longitudeDelta = fabs(tempPoint1.longitude - tempPoint2.longitude) * 1.2;
MKCoordinateRegion region = {center, locationSpan};

[mapView setRegion:region];

我有什么想法可以改变这段代码，以确保它可以处理startLong为正，即174和nextLong为负，即-127，反之亦然

Answer 1

由于startLong和nextLong是经度，因此从0°到360°，您可以确保它们都是正数，nextLong＆gt; = startLong ：

while( startLong < 0.0 ) startLong += 360.0f;
while( startLong >= 360.0 ) startLong -= 360.0f;
while( nextLong < startLong ) nextLong += 360.0f;
while( nextLong - startLong > 360.0 ) nextLong -= 360.0;

有了这个，你确定：

startLong介于0.0和360.0之间（仅限于后者）
nextLong介于startLong和startLong + 360.0

超过180度时，找到两个CLLocationCoordinate2D之间的中点

1 个答案: