使用的是百度地图SDK
导入头文件#import <BaiduMapAPI_Utils/BMKUtilsComponent.h>

[_mapView showAnnotations:tempArr animated:YES];
[self mapViewFitAnnotations:tempArr];

• (void)mapViewFitAnnotations:(NSArray *)annotations
  {
  if (annotations.count < 2) return;

  BMKPointAnnotation *annotation = annotations[0];
  CLLocationCoordinate2D coor = annotation.coordinate;
  BMKMapPoint pt = BMKMapPointForCoordinate(coor);

  CGFloat ltX, ltY, rbX, rbY;

  ltX = pt.x;
  ltY = pt.y;
  rbX = pt.x;
  rbY = pt.y;

  for (int i = 1; i < annotations.count; i++) {
  BMKPointAnnotation *annotation = annotations[i];
  CLLocationCoordinate2D coor = annotation.coordinate;
  BMKMapPoint pt = BMKMapPointForCoordinate(coor);
  if (pt.x < ltX) ltX = pt.x;
  if (pt.x > rbX) rbX = pt.x;
  if (pt.y > ltY) ltY = pt.y;
  if (pt.y < rbY) rbY = pt.y;
  }
  BMKMapRect rect;
  rect.origin = BMKMapPointMake(ltX , ltY);
  rect.size = BMKMapSizeMake(rbX - ltX, rbY - ltY);
  [_mapView setVisibleMapRect:rect];
  _mapView.zoomLevel = _mapView.zoomLevel - 2;
  }