iPhone MKMapView：設置地圖區域以顯示地圖上的所有針腳

Question

我試圖設置地圖區域（中心和跨度），以便地圖同時顯示所有針腳註釋。

我無法將長/緯度座標從NSString轉換爲double，resp。與他們進行計算。下面是我使用的代碼：

- (void)updateMemberPins{ 

//calculate new region to show on map 
double center_long = 0.0f; 
double center_lat = 0.0f; 
double max_long = 0.0f; 
double min_long = 0.0f; 
double max_lat = 0.0f; 
double min_lat = 0.0f; 

for (Member *member in members) { 

    //find min and max values 
    if ([member.locLat doubleValue] > max_lat) {max_lat = [member.locLat doubleValue];} 
    if ([member.locLat doubleValue] < min_lat) {min_lat = [member.locLat doubleValue];} 
    if ([member.locLong doubleValue] > max_long) {max_long = [member.locLong doubleValue];} 
    if ([member.locLong doubleValue] < min_long) {min_long = [member.locLong doubleValue];} 

    //sum up long and lang to get average later 
    center_lat = center_lat + [member.locLat doubleValue]; 
    center_long = center_long + [member.locLong doubleValue]; 
} 

//calculate average long/lat 
center_lat = center_lat/[members count]; 
center_long = center_long/[members count]; 

NSLog(@"center long: %d, center lat: %d", center_long, center_lat); 
NSLog(@"max_long: %d, min_long: %d, max_lat: %d, min_lat: %d", max_long, min_long, max_lat, min_lat); 

//create new region and set map 
CLLocationCoordinate2D coord = {latitude: center_lat, longitude: center_long}; 
MKCoordinateSpan span = MKCoordinateSpanMake(abs(max_lat) + abs(min_lat), abs(max_long) + abs(min_long)); 
MKCoordinateRegion region = {coord, span}; 
[resultMapView setRegion:region]; 

//remove all pins from map 
[resultMapView removeAnnotations:resultMapView.annotations]; 

//show member pins 
for (id member in members) { 
    [resultMapView addAnnotation:(Member *) member]; 
} 

}

日誌輸出的結果是：

中心長：-1946827116，中心緯度：1075651472

max_long：-6267216，min_long：1076018553，max_lat：0，min_lat：0

我瘦k問題來自（錯誤地）將NSString的值轉換爲double，但是我無法找到使其工作的方式...位置字符串的格式類似於'43.5686473'。

任何提示？ Cheerz

Answer 1

要顯示的NSLog（雙值），你應該使用%f，而不是%d 變化NSLog()部分是這樣的：

NSLog(@"center long: %f, center lat: %f", center_long, center_lat); 
NSLog(@"max_long: %f, min_long: %f, max_lat: %f, min_lat: %f", max_long, min_long, max_lat, min_lat); 

此外，使用區域從MKMapView是不是讓你自己要簡單得多。一旦設置了縮放比例，您只需要使用不同的座標動態移動地圖即可。

MKCoordinateRegion region = self.mapView.region; 
region.center = centerCoordinate; 
region.span.longitudeDelta /= ratioZoomMax; // Bigger the value, closer the map view 
region.span.latitudeDelta /= ratioZoomMax; 
[self.mapView setRegion:region animated:YES]; // Choose if you want animate or not 

Answer 2

爲那些尋找類似的東西最後，工作代碼：

- (void)updateMemberPins{ 

    //remove all pins from map 
    [resultMapView removeAnnotations:resultMapView.annotations]; 

    if ([members count] > 0) { 

     @try { 
      //calculate new region to show on map   
      Member *firstMember = [members objectAtIndex:0]; 
      double max_long = [firstMember.locLong doubleValue]; 
      double min_long = [firstMember.locLong doubleValue]; 
      double max_lat = [firstMember.locLat doubleValue]; 
      double min_lat = [firstMember.locLat doubleValue]; 

      //find min and max values 
      for (Member *member in members) { 
       if ([member.locLat doubleValue] > max_lat) {max_lat = [member.locLat doubleValue];} 
       if ([member.locLat doubleValue] < min_lat) {min_lat = [member.locLat doubleValue];} 
       if ([member.locLong doubleValue] > max_long) {max_long = [member.locLong doubleValue];} 
       if ([member.locLong doubleValue] < min_long) {min_long = [member.locLong doubleValue];} 
      } 

      //calculate center of map 
      double center_long = (max_long + min_long)/2; 
      double center_lat = (max_lat + min_lat)/2; 

      //calculate deltas 
      double deltaLat = abs(max_lat - min_lat); 
      double deltaLong = abs(max_long - min_long); 

      //set minimal delta 
      if (deltaLat < 5) {deltaLat = 5;} 
      if (deltaLong < 5) {deltaLong = 5;} 

      //debug 
      //NSLog(@"center long: %f, center lat: %f", center_long, center_lat); 
      //NSLog(@"max_long: %f, min_long: %f, max_lat: %f, min_lat: %f", max_long, min_long, max_lat, min_lat); 

      //create new region and set map 
      CLLocationCoordinate2D coord = {latitude: center_lat, longitude: center_long}; 
      MKCoordinateSpan span = MKCoordinateSpanMake(deltaLat, deltaLong); 
      MKCoordinateRegion region = {coord, span}; 
      [resultMapView setRegion:region]; 


     } 
     @catch (NSException * e) { 
      NSLog(@"Error calculating new map region: %@", e); 
     } 
     @finally { 
      //show member pins 
      for (id member in members) { 
       [resultMapView addAnnotation:(Member *) member]; 
      } 
     } 



    } 

} 

Answer 3

//show member pins 
     for (id member in members) { 
      [resultMapView addAnnotation:(Member *) member]; 
     } 

這可以用

[resultMapView addAnnotations:members]; 

Answer 4

代替你可以簡單地使用此代碼和平：

-(void)updateMemberPins 
{ 
    if([members count] == 0) 
     return; 

    double minLat = 90; 
    double minLon = 180; 
    double maxLat = -90; 
    double maxLon = -180; 

    for(Member *member in members) 
    { 
     minLat = fmin(minLat, [member.locLat doubleValue]); 
     minLon = fmin(minLon, [member.locLong doubleValue]); 
     maxLat = fmax(maxLat, [member.locLat doubleValue]); 
     maxLon = fmax(maxLon, [member.locLong doubleValue]); 
    } 

    NSLog(@"MAX LAT: %f, MIN LAT: %f, MAX LONG: %f, MIN LONG: %f,", maxLat, minLat, maxLon, minLon); 

    double midLat = (minLat + maxLat)/2; 
    double midLong = (minLon + maxLon)/2; 

    double deltaLat = abs(maxLat - minLat); 
    double deltaLong = abs(maxLon - minLon); 

    if (deltaLat < 5) {deltaLat = 5;} 
    if (deltaLong < 5) {deltaLong = 5;} 

    //... 
}