iOS开发学习之MapKit - 获得在MapView（地图）中显示多个标记的区域（MKCoordinateRegion）
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-(MKCoordinateRegion)regionForAnnotations:(NSArray *)annotations //可原封不动的复制运用
{
MKCoordinateRegion region;
if([annotations count] == 0)
{
region = MKCoordinateRegionMakeWithDistance(self.mapView.userLocation.coordinate, 1000, 1000);
}
else if([annotations count] == 1)
{
id <MKAnnotation> annotation = [annotations lastObject];
region = MKCoordinateRegionMakeWithDistance(annotation.coordinate, 1000, 1000);
}
else
{
CLLocationCoordinate2D topLeftCoord;
topLeftCoord.latitude = -90;
topLeftCoord.longitude = 180;
CLLocationCoordinate2D bottomRightCoord;
bottomRightCoord.latitude = 90;
bottomRightCoord.longitude = -180;
for(id <MKAnnotation> annotation in annotations)
{
topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);
topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
}
const double extraSpace = 1.1;
region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) / 2.0;
region.center.longitude = topLeftCoord.longitude - (topLeftCoord.longitude - bottomRightCoord.longitude) / 2.0;
region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * extraSpace;
region.span.longitudeDelta = fabs(topLeftCoord.longitude - bottomRightCoord.longitude) * extraSpace;
}
return [self.mapView regionThatFits:region];
}
使用说明：
-(IBAction)showLocations
{
MKCoordinateRegion region = [self regionForAnnotations:_locations];
//调用以上方法，获得一个MKCoordinateRegion区域，该区域包含_locations里的多个标记
[self.mapView setRegion:region animated:YES];
}
注意：_locations里的对象必须实现协议MKAnnotation，并实现以下三个方法：
-(CLLocationCoordinate2D)coordinate
{
return CLLocationCoordinate2DMake([self.latitude doubleValue], [self.longitude doubleValue]);
}
-(NSString *)title
{
if([self.locationDescription length] > 0)
{
return self.locationDescription;
}
else
{
return @"(No Description)";
}
}
-(NSString *)subtitle
{
return self.category;
}
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