思路<br />
要把Track 显示到地图可见区域的中心位置，需要让map 知道Track的中心点，以及需要显示的区域，下面我们来一步一步实现。
文中locations是一个存放了CLLocation类型的一些点。
首先定义一个结构体，用来返回地图显示区域，需要的一些参数
typedef struct {
CLLocationDistance latitudinalMeters; //纬度距离
CLLocationDistance longitudinalMeters; //经度距离
CLLocationCoordinate2D centerCoord; //地图中心点
} CoordinateRegion;
通过找出Track上经纬度最大点和最小点，取平均值可以拿到中心点。
通过计算Track上起点和终点的经度最大距离/纬度最大距离，可以定制Map的显示区域。
/**
* 找出地图可显示区域参数
* @param locations 存放地图CLLocation点的数组
* @return CoordinateRegion(经度距离、纬度距离、地图中心点)
*/
- (CoordinateRegion *)makeCoordinateCoordinateRegionWithLocation:(NSArray *)locations {
CoordinateRegion *coordinateRegion = malloc(sizeof(CoordinateRegion));
NSArray *latitudes = [self rankRouteWithLocations:locations latitude:YES];
NSArray *longitudes = [self rankRouteWithLocations:locations latitude:NO];
// 找到地图中的最大点和小点
CLLocation *MinLatitude = [latitudes firstObject];
CLLocation *MaxLatitude = [latitudes lastObject];
CLLocation *MinLongitude = [longitudes firstObject];
CLLocation *MaxLongitude = [longitudes lastObject];
// 转成CLLocationDegrees
CLLocationDegrees MinLatitudeDegrees = MinLatitude.coordinate.latitude;
CLLocationDegrees MaxLatitudeDegrees = MaxLatitude.coordinate.latitude;
CLLocationDegrees MinLongitudeDegrees = MinLongitude.coordinate.longitude;
CLLocationDegrees MaxLongitudeDegrees = MaxLongitude.coordinate.longitude;
CLLocationDegrees centerLa = (MinLatitudeDegrees + MaxLatitudeDegrees)/2; // 纬度中心点
CLLocationDegrees centerLo = (MinLongitudeDegrees + MaxLongitudeDegrees)/2;// 经度中心店
// 计算经纬度 最远点和最近点之前的距离
CLLocationDistance latitudeDistance = [MinLatitude distanceFromLocation:MaxLatitude] + 100;
CLLocationDistance longitudeDistance = [MinLongitude distanceFromLocation:MaxLongitude] + 100;
CLLocationCoordinate2D centerCoord = CLLocationCoordinate2DMake(centerLa, centerLo);
coordinateRegion->latitudinalMeters = latitudeDistance;
coordinateRegion->longitudinalMeters = longitudeDistance;
coordinateRegion->centerCoord = centerCoord;
return coordinateRegion;
}
关于经/纬度点的排序方法，请看下面
/**
* 排序
* @param locations 存放地图CLLocation点的数组
* @param isLatitude 按照纬度排序
* @return 排序后的经度/ 纬度 CLLocation 数组
*/
-(NSArray*)rankRouteWithLocations:(NSArray *)locations latitude:(BOOL)isLatitude
{
NSMutableArray *pointArray=[NSMutableArray arrayWithArray:locations];
NSSortDescriptor *sort1 = [NSSortDescriptor sortDescriptorWithKey:@"self" ascending:YES
comparator:^NSComparisonResult(id obj1, id obj2) {
CLLocation *point1= obj1;
CLLocation *point2 = obj2;
double lat1 = isLatitude?point1.coordinate.latitude:point1.coordinate.longitude;
double lat2 = isLatitude?point2.coordinate.latitude:point2.coordinate.longitude;
if (lat1 > lat2) {
return NSOrderedDescending;
}else if (lat1 < lat2) {
return NSOrderedAscending;
}else{
return NSOrderedSame;
}
}];
[pointArray sortUsingDescriptors:[NSArray arrayWithObject:sort1]];
return pointArray;
}
最后一步，给Map 设置显示区域
/**
* 地图显示区域
* @param locations 存放地图CLLocation点的数组
*/
- (void)mapTrackShowRegionWithLocation:(NSArray *)locations {
// 地图缩放显示。缩放区域
MKCoordinateSpan span;
span.latitudeDelta = 0.003f;
span.longitudeDelta = 0.003f;
CoordinateRegion *reginCoordinate = [self makeCoordinateCoordinateRegionWithLocation:locations];
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(reginCoordinate->centerCoord, reginCoordinate->latitudinalMeters, reginCoordinate->longitudinalMeters);
[_mapView regionThatFits:region];
[_mapView setRegion:region animated:YES];
}
效果图如下：
Track
